Bio

Academic Appointments


Administrative Appointments


  • Scientific Advisory Board, Founding Member, The Stem Cell Advisors (2008 - Present)
  • Visiting Professor, Institute of Neuroscience, Chinese Academy of Sciences, Shanghai (2005 - Present)
  • Adjunct Associate Research Scientist, The Parkinson's Institute, Sunnyvale, CA (2005 - Present)
  • Scientific Advisory Board, Children's Neurobiological Solutions (2005 - Present)
  • Committee Chair, Stanford Stem Cell Research Oversight Committee (2006 - 2009)
  • Scientific Advisory Board, Michael J. Fox Foundation (2002 - 2010)
  • Scientific Advisor, Kinetics Foundation (2001 - 2007)

Honors & Awards


  • Blume Award in Parkinson's Disease Research, Blume Foundation (2007-2012)
  • Hearst Faculty Scholar, Hearst Foundation (2007)
  • Kinetics Foundation Award for Research in Stem Cell Biology, The Kinetics Foundation (2004)
  • Grass Lectureship, The Grass Foundation (2003)
  • Margot Anderson Wings of Hope Award, Margot Anderson Foundation (2002)
  • Mitsubishi Pharma Stem Cell Research Award, Mitsubishi Pharma Inc. (2002)
  • Michael J Fox Fellowship in Stem Cell Research at Stanford, Michael J. Fox Foundation (2002)
  • Judith Graham Pool Award, National Hemophilia Foundation (1991)

Professional Education


  • BS, Andrews University, Biology (1981)
  • Ph.D., University of Washington, Experimental Pathology (1990)

Community and International Work


  • Route 28 Summits in Neurobiology

    Topic

    Current Topics in Biomedical Research

    Partnering Organization(s)

    Stanford, University of Washington, Max Delbruck Center Berlin, University of Gothenburg

    Populations Served

    Graduate and Postgraduate Students

    Location

    International

    Ongoing Project

    Yes

    Opportunities for Student Involvement

    Yes

  • Working Group in Parkinson's Disease at Stanford

    Topic

    Parkinson's Disease Research

    Partnering Organization(s)

    Stanford University, The Parkinson's Institute, UCSF

    Populations Served

    Parkinson's Disease Research and Patient Communities

    Location

    International

    Ongoing Project

    Yes

    Opportunities for Student Involvement

    Yes

Research & Scholarship

Current Research and Scholarly Interests


Human brain development and maintenance is orchestrated by a complex interaction of genetic and environmental factors. Our research examines how neural stem cells respond to these cues to add and integrate new neurons into functional circuits.

NEURAL STEM CELLS IN DEVELOPMENT: Our studies of neurogenesis in the developing brain focus on the influence of maternal health or illness on fetal brain development. In mice, even mild maternal illness during early pregnancy can alter stem cell activity in the developing fetal brain. This leads to subtle changes in social behavior and cognition reminiscent of autism. Prior epidemiological studies have noted that autoimmune events, allergies, or infections during pregnancy may increase the risk of autism in the child. Our ongoing research focuses on genetic risk factors for autism that may exacerbate the effects of maternal illness on fetal brain development.

NEURAL STEM CELLS IN THE ADULT: Our studies of stem cells in the adult focus on the hippocampus, one of the few areas where neurogenesis naturally continues throughout life. We have found that this region contains a unique arrangement of cells and signals that instruct stem cells to generate new neurons. Our goal is to determine if manipulating these signals might augment neurogenesis and enhance stem cell mediated CNS repair.

STEM CELLS TO STUDY CNS INJURY AND DISEASE: Using information gained from studying neural stem cells in development and in the adult, we have been able to reconstruct the conditions of neurogenesis in the Petri dish. We are now able to use human embryonic stem cells and non-embryonic induced pluripotent stem cells to generate several types of human neurons, including those lost in Parkinson’s disease.

Pluripotent stem cells from patients who suffer from neurological disorders promise to be fundamentally important tools for identifying disease mechanisms or for providing neurons for repair. Understanding how new neurons are produced, and more importantly integrated, is critical for guiding efforts to restore function. With sufficient insights into the native control of neurogenesis, it may be possible to ameliorate the devastating effects of neurodevelopmental disease, injury, or aging-related disorders such as Parkinson’s or Alzheimer’s disease.

Teaching

2013-14 Courses


Publications

Journal Articles


  • PET Imaging of Stroke-Induced Neuroinflammation in Mice Using [F-18]PBR06 MOLECULAR IMAGING AND BIOLOGY Lartey, F. M., Ahn, G., Shen, B., Cord, K., Smith, T., Chua, J. Y., Rosenblum, S., Liu, H., James, M. L., Chernikova, S., Lee, S. W., Pisani, L. J., Tirouvanziam, R., Chen, J. W., Palmer, T. D., Chin, F. T., Guzman, R., Graves, E. E., Loo, B. W. 2014; 16 (1): 109-117

    Abstract

    The purpose of this study is to evaluate the 18 kDa translocator protein (TSPO) radioligand [(18)F]N-fluoroacetyl-N-(2,5-dimethoxybenzyl)-2-phenoxyaniline ([(18)F]PBR06) as a positron emission tomography (PET) imaging biomarker of stroke-induced neuroinflammation in a rodent model.Stroke was induced by transient middle cerebral artery occlusion in Balb/c mice. Dynamic PET/CT imaging with displacement and preblocking using PK111195 was performed 3 days later. PET data were correlated with immunohistochemistry (IHC) for the activated microglial markers TSPO and CD68 and with autoradiography.[(18)F]PBR06 accumulation peaked within the first 5 min postinjection, then decreased gradually, remaining significantly higher in infarct compared to noninfarct regions. Displacement or preblocking with PK11195 eliminated the difference in [(18)F]PBR06 uptake between infarct and noninfarct regions. Autoradiography and IHC correlated well spatially with uptake on PET.[(18)F]PBR06 PET specifically images TSPO in microglial neuroinflammation in a mouse model of stroke and shows promise for imaging and monitoring microglial activation/neuroinflammation in other disease models.

    View details for DOI 10.1007/s11307-013-0664-5

    View details for Web of Science ID 000329793200014

    View details for PubMedID 23836504

  • Neuronal Rac1 Is Required for Learning-Evoked Neurogenesis JOURNAL OF NEUROSCIENCE Haditsch, U., Anderson, M. P., Freewoman, J., Cord, B., Babu, H., Brakebusch, C., Palmer, T. D. 2013; 33 (30): 12229-12241

    Abstract

    Hippocampus-dependent learning and memory relies on synaptic plasticity as well as network adaptations provided by the addition of adult-born neurons. We have previously shown that activity-induced intracellular signaling through the Rho family small GTPase Rac1 is necessary in forebrain projection neurons for normal synaptic plasticity in vivo, and here we show that selective loss of neuronal Rac1 also impairs the learning-evoked increase in neurogenesis in the adult mouse hippocampus. Earlier work has indicated that experience elevates the abundance of adult-born neurons in the hippocampus primarily by enhancing the survival of neurons produced just before the learning event. Loss of Rac1 in mature projection neurons did reduce learning-evoked neurogenesis but, contrary to our expectations, these effects were not mediated by altering the survival of young neurons in the hippocampus. Instead, loss of neuronal Rac1 activation selectively impaired a learning-evoked increase in the proliferation and accumulation of neural precursors generated during the learning event itself. This indicates that experience-induced alterations in neurogenesis can be mechanistically resolved into two effects: (1) the well documented but Rac1-independent signaling cascade that enhances the survival of young postmitotic neurons; and (2) a previously unrecognized Rac1-dependent signaling cascade that stimulates the proliferative production and retention of new neurons generated during learning itself.

    View details for DOI 10.1523/JNEUROSCI.2939-12.2013

    View details for Web of Science ID 000322168600010

    View details for PubMedID 23884931

  • Absence of CCL2 is sufficient to restore hippocampal neurogenesis following cranial irradiation. Brain, behavior, and immunity Lee, S. W., Haditsch, U., Cord, B. J., Guzman, R., Kim, S. J., Boettcher, C., Priller, J., Ormerod, B. K., Palmer, T. D. 2013; 30: 33-44

    Abstract

    Cranial irradiation for the treatment of brain tumors causes a delayed and progressive cognitive decline that is pronounced in young patients. Dysregulation of neural stem and progenitor cells is thought to contribute to these effects by altering early childhood brain development. Earlier work has shown that irradiation creates a chronic neuroinflammatory state that severely and selectively impairs postnatal and adult neurogenesis. Here we show that irradiation induces a transient non-classical cytokine response with selective upregulation of CCL2/monocyte chemoattractant protein-1 (MCP-1). Absence of CCL2 signaling in the hours after irradiation is alone sufficient to attenuate chronic microglia activation and allow the recovery of neurogenesis in the weeks following irradiation. This identifies CCL2 signaling as a potential clinical target for moderating the long-term defects in neural stem cell function following cranial radiation in children.

    View details for DOI 10.1016/j.bbi.2012.09.010

    View details for PubMedID 23041279

  • Differential roles of TNFR1 and TNFR2 signaling in adult hippocampal neurogenesis. Brain, behavior, and immunity Chen, Z., Palmer, T. D. 2013; 30: 45-53

    Abstract

    Tumor necrosis factor alpha (TNF?) is a potent inhibitor of neurogenesis in vitro but here we show that TNF? signaling has both positive and negative effects on neurogenesis in vivo and is required to moderate the negative impact of cranial irradiation on hippocampal neurogenesis. In vitro, basal levels of TNF? signaling through TNFR2 are required for normal neural progenitor cell proliferation while basal signaling through TNFR1 impairs neural progenitor proliferation. TNFR1 also mediates further reductions in proliferation and elevated cell death following exposure to recombinant TNF?. In vivo, TNFR1(-/-) and TNF?(-/-) animals have elevated baseline neurogenesis in the hippocampus, whereas absence of TNFR2 decreases baseline neurogenesis. TNF? is also implicated in defects in neurogenesis that follow radiation injury but we find that loss of TNFR1 has no protective effects on neurogenesis and loss of TNF? or TNFR2 worsened the effects of radiation injury on neurogenesis. We conclude that the immunomodulatory signaling of TNF? mediated by TNFR2 is more significant to radiation injury outcome than the proinflammatory signaling mediated through TNFR1.

    View details for DOI 10.1016/j.bbi.2013.01.083

    View details for PubMedID 23402793

  • Lineage tracing with Axin2 reveals distinct developmental and adult populations of Wnt/ß-catenin-responsive neural stem cells. Proceedings of the National Academy of Sciences of the United States of America Bowman, A. N., van Amerongen, R., Palmer, T. D., Nusse, R. 2013; 110 (18): 7324-7329

    Abstract

    Since the discovery of neural stem cells in the mammalian brain, there has been significant interest in understanding their contribution to tissue homeostasis at both the cellular and molecular level. Wnt/?-catenin signaling is crucial for development of the central nervous system and has been implicated in stem cell maintenance in multiple tissues. Based on this, we hypothesized that the Wnt pathway likely controls neural stem cell maintenance and differentiation along the entire developmental continuum. To test this, we performed lineage tracing experiments using the recently developed tamoxifen-inducible Cre at Axin2 mouse strain to follow the developmental fate of Wnt/?-catenin-responsive cells in both the embryonic and postnatal mouse brain. From as early as embryonic day 8.5 onwards, Axin2(+) cells can give rise to spatially and functionally restricted populations of adult neural stem cells in the subventricular zone. Similarly, progeny from Axin2(+) cells labeled from E12.5 contribute to both the subventricular zone and the dentate gyrus of the hippocampus. Labeling in the postnatal brain, in turn, demonstrates the persistence of long-lived, Wnt/?-catenin-responsive stem cells in both of these sites. These results demonstrate the continued importance of Wnt/?-catenin signaling for neural stem and progenitor cell formation and function throughout developmental time.

    View details for DOI 10.1073/pnas.1305411110

    View details for PubMedID 23589866

  • PPAR gamma activation prevents impairments in spatial memory and neurogenesis following transient illness BRAIN BEHAVIOR AND IMMUNITY Ormerod, B. K., Hanft, S. J., Asokan, A., Haditsch, U., Lee, S. W., Palmer, T. D. 2013; 29: 28-38

    Abstract

    The detrimental effects of illness on cognition are familiar to virtually everyone. Some effects resolve quickly while others may linger after the illness resolves. We found that a transient immune response stimulated by lipopolysaccharide (LPS) compromised hippocampal neurogenesis and impaired hippocampus-dependent spatial memory. The immune event caused an ?50% reduction in the number of neurons generated during the illness and the onset of the memory impairment was delayed and coincided with the time when neurons generated during the illness would have become functional within the hippocampus. Broad spectrum non-steroidal anti-inflammatory drugs attenuated these effects but selective Cox-2 inhibition was ineffective while PPAR? activation was surprisingly effective at protecting both neurogenesis and memory from the effects of LPS-produced transient illness. These data may highlight novel mechanisms behind chronic inflammatory and neuroinflammatory episodes that are known to compromise hippocampus-dependent forms of learning and memory.

    View details for DOI 10.1016/j.bbi.2012.10.017

    View details for Web of Science ID 000315365400004

    View details for PubMedID 23108061

  • Neuronal rac1 is required for learning-evoked neurogenesis. The Journal of neuroscience : the official journal of the Society for Neuroscience Haditsch, U., Anderson, M. P., Freewoman, J., Cord, B., Babu, H., Brakebusch, C., Palmer, T. D. 2013; 33 (30): 12229-41

    Abstract

    Hippocampus-dependent learning and memory relies on synaptic plasticity as well as network adaptations provided by the addition of adult-born neurons. We have previously shown that activity-induced intracellular signaling through the Rho family small GTPase Rac1 is necessary in forebrain projection neurons for normal synaptic plasticity in vivo, and here we show that selective loss of neuronal Rac1 also impairs the learning-evoked increase in neurogenesis in the adult mouse hippocampus. Earlier work has indicated that experience elevates the abundance of adult-born neurons in the hippocampus primarily by enhancing the survival of neurons produced just before the learning event. Loss of Rac1 in mature projection neurons did reduce learning-evoked neurogenesis but, contrary to our expectations, these effects were not mediated by altering the survival of young neurons in the hippocampus. Instead, loss of neuronal Rac1 activation selectively impaired a learning-evoked increase in the proliferation and accumulation of neural precursors generated during the learning event itself. This indicates that experience-induced alterations in neurogenesis can be mechanistically resolved into two effects: (1) the well documented but Rac1-independent signaling cascade that enhances the survival of young postmitotic neurons; and (2) a previously unrecognized Rac1-dependent signaling cascade that stimulates the proliferative production and retention of new neurons generated during learning itself.

    View details for PubMedID 23884931

  • Adult neural progenitor cells reactivate superbursting in mature neural networks EXPERIMENTAL NEUROLOGY Stephens, C. L., Toda, H., Palmer, T. D., DeMarse, T. B., Ormerod, B. K. 2012; 234 (1): 20-30

    Abstract

    Behavioral recovery in animal models of human CNS syndromes suggests that transplanted stem cell derivatives can augment damaged neural networks but the mechanisms behind potentiated recovery remain elusive. Here we use microelectrode array (MEA) technology to document neural activity and network integration as rat primary neurons and rat hippocampal neural progenitor cells (NPCs) differentiate and mature. The natural transition from neuroblast to functional excitatory neuron consists of intermediate phases of differentiation characterized by coupled activity. High-frequency network-wide bursting or "superbursting" is a hallmark of early plasticity that is ultimately refined into mature stable neural network activity. Microelectrode array (MEA)-plated neurons transition through this stage of coupled superbursting before establishing mature neuronal phenotypes in vitro. When plated alone, adult rat hippocampal NPC-derived neurons fail to establish the synchronized bursting activity that neurons in primary and embryonic stem cell-derived cultures readily form. However, adult rat hippocampal NPCs evoke re-emergent superbursting in electrophysiologically mature rat primary neural cultures. Developmental superbursting is thought to accompany transient states of heightened plasticity both in culture preparations and across brain regions. Future work exploring whether NPCs can re-stimulate developmental states in injury models would be an interesting test of their regenerative potential.

    View details for DOI 10.1016/j.expneurol.2011.12.009

    View details for Web of Science ID 000301617500004

    View details for PubMedID 22198136

  • Using iPSC-derived neurons to uncover cellular phenotypes associated with Timothy syndrome NATURE MEDICINE Pasca, S. P., Portmann, T., Voineagu, I., Yazawa, M., Shcheglovitov, A., Pasca, A. M., Cord, B., Palmer, T. D., Chikahisa, S., Nishino, S., Bernstein, J. A., Hallmayer, J., Geschwind, D. H., Dolmetsch, R. E. 2011; 17 (12): 1657-U176

    Abstract

    Monogenic neurodevelopmental disorders provide key insights into the pathogenesis of disease and help us understand how specific genes control the development of the human brain. Timothy syndrome is caused by a missense mutation in the L-type calcium channel Ca(v)1.2 that is associated with developmental delay and autism. We generated cortical neuronal precursor cells and neurons from induced pluripotent stem cells derived from individuals with Timothy syndrome. Cells from these individuals have defects in calcium (Ca(2+)) signaling and activity-dependent gene expression. They also show abnormalities in differentiation, including decreased expression of genes that are expressed in lower cortical layers and in callosal projection neurons. In addition, neurons derived from individuals with Timothy syndrome show abnormal expression of tyrosine hydroxylase and increased production of norepinephrine and dopamine. This phenotype can be reversed by treatment with roscovitine, a cyclin-dependent kinase inhibitor and atypical L-type-channel blocker. These findings provide strong evidence that Ca(v)1.2 regulates the differentiation of cortical neurons in humans and offer new insights into the causes of autism in individuals with Timothy syndrome.

    View details for DOI 10.1038/nm.2576

    View details for Web of Science ID 000297978000039

    View details for PubMedID 22120178

  • SNCA Triplication Parkinson's Patient's iPSC-derived DA Neurons Accumulate alpha-Synuclein and Are Susceptible to Oxidative Stress PLOS ONE Byers, B., Cord, B., Ha Nam Nguyen, H. N., Schuele, B., Fenno, L., Lee, P. C., Deisseroth, K., Langston, J. W., Pera, R. R., Palmer, T. D. 2011; 6 (11)

    Abstract

    Parkinson's disease (PD) is an incurable age-related neurodegenerative disorder affecting both the central and peripheral nervous systems. Although common, the etiology of PD remains poorly understood. Genetic studies infer that the disease results from a complex interaction between genetics and environment and there is growing evidence that PD may represent a constellation of diseases with overlapping yet distinct underlying mechanisms. Novel clinical approaches will require a better understanding of the mechanisms at work within an individual as well as methods to identify the specific array of mechanisms that have contributed to the disease. Induced pluripotent stem cell (iPSC) strategies provide an opportunity to directly study the affected neuronal subtypes in a given patient. Here we report the generation of iPSC-derived midbrain dopaminergic neurons from a patient with a triplication in the ?-synuclein gene (SNCA). We observed that the iPSCs readily differentiated into functional neurons. Importantly, the PD-affected line exhibited disease-related phenotypes in culture: accumulation of ?-synuclein, inherent overexpression of markers of oxidative stress, and sensitivity to peroxide induced oxidative stress. These findings show that the dominantly-acting PD mutation is intrinsically capable of perturbing normal cell function in culture and confirm that these features reflect, at least in part, a cell autonomous disease process that is independent of exposure to the entire complexity of the diseased brain.

    View details for DOI 10.1371/journal.pone.0026159

    View details for Web of Science ID 000297555400007

    View details for PubMedID 22110584

  • The CCR2/CCL2 Interaction Mediates the Transendothelial Recruitment of Intravascularly Delivered Neural Stem Cells to the Ischemic Brain STROKE Andres, R. H., Choi, R., Pendharkar, A. V., Gaeta, X., Wang, N., Nathan, J. K., Chua, J. Y., Lee, S. W., Palmer, T. D., Steinberg, G. K., Guzman, R. 2011; 42 (10): 2923-U387

    Abstract

    The inflammatory response is a critical component of ischemic stroke. In addition to its physiological role, the mechanisms behind transendothelial recruitment of immune cells also offer a unique therapeutic opportunity for translational stem cell therapies. Recent reports have demonstrated homing of neural stem cells (NSC) into the injured brain areas after intravascular delivery. However, the mechanisms underlying the process of transendothelial recruitment remain largely unknown. Here we describe the critical role of the chemokine CCL2 and its receptor CCR2 in targeted homing of NSC after ischemia.Twenty-four hours after induction of stroke using the hypoxia-ischemia model in mice CCR2+/+ and CCR2-/- reporter NSC were intra-arterially delivered. Histology and bioluminescence imaging were used to investigate NSC homing to the ischemic brain. Functional outcome was assessed with the horizontal ladder test.Using NSC isolated from CCR2+/+ and CCR2-/- mice, we show that receptor deficiency significantly impaired transendothelial diapedesis specifically in response to CCL2. Accordingly, wild-type NSC injected into CCL2-/- mice exhibited significantly decreased homing. Bioluminescence imaging showed robust recruitment of CCR2+/+ cells within 6 hours after transplantation in contrast to CCR2-/- cells. Mice receiving CCR2+/+ grafts after ischemic injury showed a significantly improved recovery of neurological deficits as compared to animals with transplantation of CCR2-/- NSC.The CCL2/CCR2 interaction is critical for transendothelial recruitment of intravascularly delivered NSC in response to ischemic injury. This finding could have significant implications in advancing minimally invasive intravascular therapeutics for regenerative medicine or cell-based drug delivery systems for central nervous system diseases.

    View details for DOI 10.1161/STROKEAHA.110.606368

    View details for Web of Science ID 000295217100052

    View details for PubMedID 21836091

  • Placental TNF-alpha Signaling in Illness-Induced Complications of Pregnancy AMERICAN JOURNAL OF PATHOLOGY Carpentier, P. A., Dingman, A. L., Palmer, T. D. 2011; 178 (6): 2802-2810

    Abstract

    Maternal infections are implicated in a variety of complications during pregnancy, including pregnancy loss, prematurity, and increased risk of neurodevelopmental disorders in the child. Here, we show in mice that even mild innate immune activation by low-dose lipopolysaccharide in early pregnancy causes hemorrhages in the placenta and increases the risk of pregnancy loss. Surviving fetuses exhibit hypoxia in the brain and impaired fetal neurogenesis. Maternal Toll-like receptor 4 signaling is a critical mediator of this process, and its activation is accompanied by elevated proinflammatory cytokines in the placenta. We evaluated the role of tumor necrosis factor-? (TNF-?) signaling and show that TNF receptor 1 (TNFR1) is necessary for the illness-induced placental pathology, accompanying fetal hypoxia, and neuroproliferative defects in the fetal brain. We also show that placental TNFR1 in the absence of maternal TNFR1 is sufficient for placental pathology to develop and that a clinically relevant TNF-? antagonist prevents placental pathology and fetal loss. Our observations suggest that the placenta is highly sensitive to proinflammatory signaling in early pregnancy and that TNF-? is an effective target for preventing illness-related placental defects and related risks to the fetus and fetal brain development.

    View details for DOI 10.1016/j.ajpath.2011.02.042

    View details for Web of Science ID 000298306900035

    View details for PubMedID 21641402

  • MHC Mismatch Inhibits Neurogenesis and Neuron Maturation in Stem Cell Allografts PLOS ONE Chen, Z., Phillips, L. K., Gould, E., Campisi, J., Lee, S. W., Ormerod, B. K., Zwierzchoniewska, M., Martinez, O. M., Palmer, T. D. 2011; 6 (3)

    Abstract

    The role of histocompatibility and immune recognition in stem cell transplant therapy has been controversial, with many reports arguing that undifferentiated stem cells are protected from immune recognition due to the absence of major histocompatibility complex (MHC) markers. This argument is even more persuasive in transplantation into the central nervous system (CNS) where the graft rejection response is minimal.In this study, we evaluate graft survival and neuron production in perfectly matched vs. strongly mismatched neural stem cells transplanted into the hippocampus in mice. Although allogeneic cells survive, we observe that MHC-mismatch decreases surviving cell numbers and strongly inhibits the differentiation and retention of graft-derived as well as endogenously produced new neurons. Immune suppression with cyclosporine-A did not improve outcome but non-steroidal anti-inflammatory drugs, indomethacin or rosiglitazone, were able to restore allogeneic neuron production, integration and retention to the level of syngeneic grafts.These results suggest an important but unsuspected role for innate, rather than adaptive, immunity in the survival and function of MHC-mismatched cellular grafts in the CNS.

    View details for DOI 10.1371/journal.pone.0014787

    View details for Web of Science ID 000289055700001

    View details for PubMedID 21479168

  • LRRK2 mutant iPSC-derived DA neurons demonstrate increased susceptibility to oxidative stress. Cell stem cell Nguyen, H. N., Byers, B., Cord, B., Shcheglovitov, A., Byrne, J., Gujar, P., Kee, K., Schüle, B., Dolmetsch, R. E., Langston, W., Palmer, T. D., Pera, R. R. 2011; 8 (3): 267-280

    Abstract

    Studies of Parkinson's disease (PD) have been hindered by lack of access to affected human dopaminergic (DA) neurons. Here, we report generation of induced pluripotent stem cells that carry the p.G2019S mutation (G2019S-iPSCs) in the Leucine-Rich Repeat Kinase-2 (LRRK2) gene, the most common PD-related mutation, and their differentiation into DA neurons. The high penetrance of the LRRK2 mutation and its clinical resemblance to sporadic PD suggest that these cells could provide a valuable platform for disease analysis and drug development. We found that DA neurons derived from G2019S-iPSCs showed increased expression of key oxidative stress-response genes and ?-synuclein protein. The mutant neurons were also more sensitive to caspase-3 activation and cell death caused by exposure to stress agents, such as hydrogen peroxide, MG-132, and 6-hydroxydopamine, than control DA neurons. This enhanced stress sensitivity is consistent with existing understanding of early PD phenotypes and represents a potential therapeutic target.

    View details for DOI 10.1016/j.stem.2011.01.013

    View details for PubMedID 21362567

  • Transplanted Stem Cell-Secreted Vascular Endothelial Growth Factor Effects Poststroke Recovery, Inflammation, and Vascular Repair STEM CELLS Horie, N., Pereira, M. P., Niizuma, K., Sun, G., Keren-Gill, H., Encarnacion, A., Shamloo, M., Hamilton, S. A., Jiang, K., Huhn, S., Palmer, T. D., Bliss, T. M., Steinberg, G. K. 2011; 29 (2): 274-285

    Abstract

    Cell transplantation offers a novel therapeutic strategy for stroke; however, how transplanted cells function in vivo is poorly understood. We show for the first time that after subacute transplantation into the ischemic brain of human central nervous system stem cells grown as neurospheres (hCNS-SCns), the stem cell-secreted factor, human vascular endothelial growth factor (hVEGF), is necessary for cell-induced functional recovery. We correlate this functional recovery to hVEGF-induced effects on the host brain including multiple facets of vascular repair and its unexpected suppression of the inflammatory response. We found that transplanted hCNS-SCns affected multiple parameters in the brain with different kinetics: early improvement in blood-brain barrier integrity and suppression of inflammation was followed by a delayed spatiotemporal regulated increase in neovascularization. These events coincided with a bimodal pattern of functional recovery, with, an early recovery independent of neovascularization, and a delayed hVEGF-dependent recovery coincident with neovascularization. Therefore, cell transplantation therapy offers an exciting multimodal strategy for brain repair in stroke and potentially other disorders with a vascular or inflammatory component.

    View details for DOI 10.1002/stem.584

    View details for Web of Science ID 000287698600011

    View details for PubMedID 21732485

  • A protocol for isolation and enriched monolayer cultivation of neural precursor cells from mouse dentate gyrus. Frontiers in neuroscience Babu, H., Claasen, J., Kannan, S., Rünker, A. E., Palmer, T., Kempermann, G. 2011; 5: 89-?

    Abstract

    In vitro assays are valuable tools to study the characteristics of adult neural precursor cells under controlled conditions with a defined set of parameters. We here present a detailed protocol based on our previous original publication (Babu et al., 2007) to isolate neural precursor cells from the hippocampus of adult mice and maintain and propagate them as adherent monolayer cultures. The strategy is based on the use of Percoll density gradient centrifugation to enrich precursor cells from the micro-dissected dentate gyrus. Based on the expression of Nestin and Sox2, a culture-purity of more than 98% can be achieved. The cultures are expanded under serum-free conditions in Neurobasal A medium with addition of the mitogens Epidermal growth factor and Fibroblast growth factor 2 as well as the supplements Glutamax-1 and B27. Under differentiation conditions, the precursor cells reliably generate approximately 30% neurons with appropriate morphological, molecular, and electrophysiological characteristics that might reflect granule cell properties as their in vivo counterpart. We also highlight potential modifications to the protocol.

    View details for DOI 10.3389/fnins.2011.00089

    View details for PubMedID 21811434

  • Transplanted Stem Cell-Secreted VEGF Effects Post-Stroke Recovery, Inflammation, and Vascular Repair. Stem cells (Dayton, Ohio) Horie, N., Pereira, M. P., Niizuma, K., Sun, G., Keren-Gill, H., Encarnacion, A., Shamloo, M., Hamilton, S. A., Jiang, K., Huhn, S., Palmer, T. D., Bliss, T. M., Steinberg, G. K. 2011

    Abstract

    Cell transplantation offers a novel therapeutic strategy for stroke; however, how transplanted cells function in vivo is poorly understood. We show for the first time that after sub-acute transplantation into the ischemic brain of human central nervous system stem cells grown as neurospheres (hCNS-SCns), the stem cell-secreted factor, human VEGF (hVEGF), is necessary for cell-induced functional recovery. We correlate this functional recovery to hVEGF-induced effects on the host brain including multiple facets of vascular repair, and its unexpected suppression of the inflammatory response. We found that transplanted hCNS-SCns affected multiple parameters in the brain with different kinetics: early improvement in blood-brain barrier (BBB) integrity and suppression of inflammation was followed by a delayed spatio-temporal regulated increase in neovascularization. These events coincided with a bi-modal pattern of functional recovery: an early recovery independent of neovascularization, and a delayed hVEGF-dependent recovery coincident with neovascularization. Therefore, cell transplantation therapy offers an exciting multi-modal strategy for brain repair in stroke and potentially other disorders with a vascular or inflammatory component.

    View details for PubMedID 21240943

  • Characterization of axon guidance cue sensitivity of human embryonic stem cell-derived dopaminergic neurons MOLECULAR AND CELLULAR NEUROSCIENCE Cord, B. J., Li, J., Works, M., McConnell, S. K., Palmer, T., Hynes, M. A. 2010; 45 (4): 324-334

    Abstract

    Dopaminergic neurons derived from human embryonic stem cells will be useful in future transplantation studies of Parkinson's disease patients. As newly generated neurons must integrate and reconnect with host cells, the ability of hESC-derived neurons to respond to axon guidance cues will be critical. Both Netrin-1 and Slit-2 guide rodent embryonic dopaminergic (DA) neurons in vitro and in vivo, but very little is known about the response of hESC-derived DA neurons to any axonal guidance cues. Here we examined the ability of Netrin-1 and Slit-2 to affect human ESC DA axons in vitro. hESC DA neurons mature over time in culture with the developmental profile of DA neurons in vivo, including expression of the DA neuron markers FoxA2, En-1 and Nurr-1, and receptors for both Netrin and Slit. hESC DA neurons respond to exogenous Netrin-1 and Slit-2, showing an increased responsiveness to Netrin-1 as the neurons mature in culture. These responses were maintained in the presence of pro-inflammatory cytokines that might be encountered in the diseased brain. These studies are the first to evaluate and confirm that suitably matured human ES-derived DA neurons can respond appropriately to axon guidance cues.

    View details for DOI 10.1016/j.mcn.2010.07.004

    View details for Web of Science ID 000283970100002

    View details for PubMedID 20637284

  • Mitochondrial Protection Attenuates Inflammation-Induced Impairment of Neurogenesis In Vitro and In Vivo JOURNAL OF NEUROSCIENCE Voloboueva, L. A., Lee, S. W., Emery, J. F., Palmer, T. D., Giffard, R. G. 2010; 30 (37): 12242-12251

    Abstract

    The impairment of hippocampal neurogenesis has been linked to the pathogenesis of neurological disorders from chronic neurodegenerative disease to the progressive cognitive impairment of children who receive brain irradiation. Numerous studies provide evidence that inflammation downregulates neurogenesis, with multiple factors contributing to this impairment. Although mitochondria are one of the primary targets of inflammatory injury, the role of mitochondrial function in the modulation of neurogenesis remains relatively unstudied. In this study, we used neurosphere-derived cells to show that immature doublecortin (Dcx)-positive neurons are uniquely sensitive to mitochondrial inhibition, demonstrating rapid loss of mitochondrial potential and cell viability compared with glial cells and more mature neurons. Mitochondrial inhibition for 24 h produced no significant changes in astrocyte or oligodendrocyte viability, but reduced viability of mature neurons by 30%, and reduced survival of Dcx(+) cells by 60%. We demonstrate that protection of mitochondrial function with mitochondrial metabolites or the mitochondrial chaperone mtHsp75/mortalin partially reverses the inflammation-associated impairment of neurogenesis in vitro and in irradiated mice in vivo. Our findings highlight mitochondrial mechanisms involved in neurogenesis and indicate mitochondria as a potential target for protective strategies to prevent the impairment of neurogenesis by inflammation.

    View details for DOI 10.1523/JNEUROSCI.1752-10.2010

    View details for Web of Science ID 000281798700003

    View details for PubMedID 20844120

  • Murine Embryonic Stem Cell-Derived Pyramidal Neurons Integrate into the Cerebral Cortex and Appropriately Project Axons to Subcortical Targets JOURNAL OF NEUROSCIENCE Ideguchi, M., Palmer, T. D., Recht, L. D., Weimann, J. M. 2010; 30 (3): 894-904

    Abstract

    Although embryonic stem (ES) cells have been induced to differentiate into diverse neuronal cell types, the production of cortical projection neurons with the correct morphology and axonal connectivity has not been demonstrated. Here, we show that in vitro patterning is critical for generating neural precursor cells (ES-NPCs) competent to form cortical pyramidal neurons. During the first week of neural induction, these ES-NPCs begin to express genes that are specific for forebrain progenitors; an additional week of differentiation produces mature neurons with many features of cortical pyramidal neurons. After transplantation into the murine cerebral cortex, these specified ES-NPCs manifest the correct dendritic and axonal connectivity for their areal location. ES-NPCs transplanted into the deep layers of the motor cortex differentiate into layer 5 pyramidal neurons and extend axons to distant subcortical targets such as the pons and as far caudal as the pyramidal decussation and descending spinal tract and, importantly, do not extend axons to inappropriate targets such as the superior colliculus (SC). ES-NPCs transplanted into the visual cortex extend axons to the dorsal aspect of the SC and pons but avoid ventral SC and the pyramidal tract, whereas cells transplanted deep into the somatosensory cortex project axons to the ventral SC, avoiding the dorsal SC. Thus, these data establish that ES-derived cortical projection neurons can integrate into anatomically relevant circuits.

    View details for DOI 10.1523/JNEUROSCI.4318-09.2010

    View details for Web of Science ID 000273779200011

    View details for PubMedID 20089898

  • FoxO3 Regulates Neural Stem Cell Homeostasis CELL STEM CELL Renault, V. M., Rafalski, V. A., Morgan, A. A., Salih, D. A., Brett, J. O., Webb, A. E., Villeda, S. A., Thekkat, P. U., Guillerey, C., Denko, N. C., Palmer, T. D., Bufte, A. J., Brunet, A. 2009; 5 (5): 527-539

    Abstract

    In the nervous system, neural stem cells (NSCs) are necessary for the generation of new neurons and for cognitive function. Here we show that FoxO3, a member of a transcription factor family known to extend lifespan in invertebrates, regulates the NSC pool. We find that adult FoxO3(-/-) mice have fewer NSCs in vivo than wild-type counterparts. NSCs isolated from adult FoxO3(-/-) mice have decreased self-renewal and an impaired ability to generate different neural lineages. Identification of the FoxO3-dependent gene expression profile in NSCs suggests that FoxO3 regulates the NSC pool by inducing a program of genes that preserves quiescence, prevents premature differentiation, and controls oxygen metabolism. The ability of FoxO3 to prevent the premature depletion of NSCs might have important implications for counteracting brain aging in long-lived species.

    View details for DOI 10.1016/j.stem.2009.09.014

    View details for Web of Science ID 000272019500014

    View details for PubMedID 19896443

  • Immune Influence on Adult Neural Stem Cell Regulation and Function NEURON Carpentier, P. A., Palmer, T. D. 2009; 64 (1): 79-92

    Abstract

    Neural stem cells (NSCs) lie at the heart of central nervous system development and repair, and deficiency or dysregulation of NSCs or their progeny can have significant consequences at any stage of life. Immune signaling is emerging as one of the influential variables that define resident NSC behavior. Perturbations in local immune signaling accompany virtually every injury or disease state, and signaling cascades that mediate immune activation, resolution, or chronic persistence influence resident stem and progenitor cells. Some aspects of immune signaling are beneficial, promoting intrinsic plasticity and cell replacement, while others appear to inhibit the very type of regenerative response that might restore or replace neural networks lost in injury or disease. Here we review known and speculative roles that immune signaling plays in the postnatal and adult brain, focusing on how environments encountered in disease or injury may influence the activity and fate of endogenous or transplanted NSCs.

    View details for DOI 10.1016/j.neuron.2009.08.038

    View details for Web of Science ID 000271454400013

    View details for PubMedID 19840551

  • A central role for the small GTPase Rac1 in hippocampal plasticity and spatial learning and memory MOLECULAR AND CELLULAR NEUROSCIENCE Haditsch, U., Leone, D. P., Farinelli, M., Chrostek-Grashoff, A., Brakebusch, C., Mansuy, I. M., McConnell, S. K., Palmer, T. D. 2009; 41 (4): 409-419

    Abstract

    Rac1 is a member of the Rho family of small GTPases that are important for structural aspects of the mature neuronal synapse including basal spine density and shape, activity-dependent spine enlargement, and AMPA receptor clustering in vitro. Here we demonstrate that selective elimination of Rac1 in excitatory neurons in the forebrain in vivo not only affects spine structure, but also impairs synaptic plasticity in the hippocampus with consequent defects in hippocampus-dependent spatial learning. Furthermore, Rac1 mutants display deficits in working/episodic-like memory in the delayed matching-to-place (DMP) task suggesting that Rac1 is a central regulator of rapid encoding of novel spatial information in vivo.

    View details for DOI 10.1016/j.mcn.2009.04.005

    View details for Web of Science ID 000267686500003

    View details for PubMedID 19394428

  • Functional Engraftment of the Medial Ganglionic Eminence Cells in Experimental Stroke Model CELL TRANSPLANTATION Daadi, M. M., Lee, S. H., Arac, A., Grueter, B. A., Bhatnagar, R., Maag, A., Schaar, B., Malenka, R. C., Palmer, T. D., Steinberg, G. K. 2009; 18 (7): 815-826

    Abstract

    Currently there are no effective treatments targeting residual anatomical and behavioral deficits resulting from stroke. Evidence suggests that cell transplantation therapy may enhance functional recovery after stroke through multiple mechanisms. We used a syngeneic model of neural transplantation to explore graft-host communications that enhance cellular engraftment.The medial ganglionic eminence (MGE) cells were derived from 15-day-old transgenic rat embryos carrying green fluorescent protein (GFP), a marker, to easily track the transplanted cells. Adult rats were subjected to transient intraluminal occlusion of the medial cerebral artery. Two weeks after stroke, the grafts were deposited into four sites, along the rostro-caudal axis and medially to the stroke in the penumbra zone. Control groups included vehicle and fibroblast transplants. Animals were subjected to motor behavioral tests at 4 week posttransplant survival time. Morphological analysis demonstrated that the grafted MGE cells differentiated into multiple neuronal subtypes, established synaptic contact with host cells, increased the expression of synaptic markers, and enhanced axonal reorganization in the injured area. Initial patch-clamp recording demonstrated that the MGE cells received postsynaptic currents from host cells. Behavioral analysis showed reduced motor deficits in the rotarod and elevated body swing tests. These findings suggest that graft-host interactions influence the fate of grafted neural precursors and that functional recovery could be mediated by neurotrophic support, new synaptic circuit elaboration, and enhancement of the stroke-induced neuroplasticity.

    View details for DOI 10.3727/096368909X470829

    View details for Web of Science ID 000271253200013

    View details for PubMedID 19500468

  • Endogenous Wnt Signaling Maintains Neural Progenitor Cell Potency STEM CELLS Wexler, E. M., Paucer, A., Kornblum, H. I., Plamer, T. D., Geschwind, D. H. 2009; 27 (5): 1130-1141

    Abstract

    Wnt signaling regulates neural stem cell (NSC) function and development throughout an individual's lifetime. Intriguingly, adult hippocampal progenitors (AHPs) produce several Wnts, and the intracellular machinery necessary to respond to them, creating the potential for an active autocrine-signaling loop within this stem cell niche. However, the standard luciferase-based Wnt assay failed to detect this signaling loop. This assay is inherently less temporally sensitive to activity among a population of unsynchronized proliferating cells because it relies on the rapidly degrading reporter luciferase. We circumvented this limitation using a promoter assay that employs green fluorescent protein (GFP), as a relatively long-lived reporter of canonical Wnt activity. We found that at baseline, AHPs secreted functional Wnt that self-stimulates low-level canonical Wnt signaling. Elimination baseline Wnt activity, via application of an extracellular Wnt antagonist promoted neurogenesis, based on a combination of unbiased gene expression analysis and cell-fate analysis. A detailed clonal analysis of progenitors transduced with specific intracellular antagonists of canonical signaling, either Axin or truncated cadherin (beta-catenin sequestering), revealed that loss of baseline signaling depletes the population of multipotent precursors, thereby driving an increasing fraction to assume a committed cell fate (i.e., unipotent progenitors). Similarly, baseline Wnt signaling repressed differentiation of human NSCs. Although the specific Wnts produced by neural precursors vary with age and between species, their effects remain remarkably consistent. In sum, this study establishes that autonomous Wnt signaling is a conserved feature of the neurogenic niche that preserves the delicate balance between NSC maintenance and differentiation.

    View details for DOI 10.1002/stem.36

    View details for Web of Science ID 000266179500016

    View details for PubMedID 19418460

  • Wnt-mediated self-renewal of neural stem/progenitor cells PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Kalani, M. Y., Cheshier, S. H., Cord, B. J., Bababeygy, S. R., Vogel, H., Weissman, I. L., Palmer, T. D., Nusse, R. 2008; 105 (44): 16970-16975

    Abstract

    In this work we have uncovered a role for Wnt signaling as an important regulator of stem cell self-renewal in the developing brain. We identified Wnt-responsive cells in the subventricular zone of the developing E14.5 mouse brain. Responding cell populations were enriched for self-renewing stem cells in primary culture, suggesting that Wnt signaling is a hallmark of self-renewing activity in vivo. We also tested whether Wnt signals directly influence neural stem cells. Using inhibitors of the Wnt pathway, we found that Wnt signaling is required for the efficient cloning and expansion of single-cell derived populations that are able to generate new stem cells as well as neurons, astrocytes, and oligodendrocytes. The addition of exogenous Wnt3a protein enhances clonal outgrowth, demonstrating not only a critical role for the Wnt pathway for the regulation of neurogenesis but also its use for the expansion of neural stem cells in cell culture and in tissue engineering.

    View details for DOI 10.1073/pnas.0808616105

    View details for Web of Science ID 000260913800033

    View details for PubMedID 18957545

  • Long-term transgene expression in mouse neural progenitor cells modified with phi C31 integrase JOURNAL OF NEUROSCIENCE METHODS Keravala, A., Ormerod, B. K., Palmer, T. D., Calos, M. P. 2008; 173 (2): 299-305

    Abstract

    Stem cells can potentially be utilized in combined gene/cell therapies for neural diseases. We examined the ability of the non-viral phiC31 integrase system to promote stable transgene expression in mouse neural progenitor cells (mNPCs). phiC31 integrase catalyzes the sequence-specific integration of attB-containing plasmids into pseudo attP sites in mammalian genomes, to produce long-term transgene expression. We achieved gene transfer by co-nucleofection of a plasmid carrying the luciferase marker gene and an attB site and a plasmid expressing integrase in mNPCs that had been generated in a neurosphere preparation. Luciferase expression was quantified in live cells for 8 weeks, revealing persistence of gene expression. Sequence-specific integration at a preferred pseudo attP site in the mouse genome was detected by using PCR. Furthermore, sustained transgene expression was demonstrated in genetically modified NPCs that were cultured in conditions that promoted either growth or differentiation into neurons and astrocytes. Our results demonstrate that the phiC31 integrase system produces stable transgene expression in adult mNPCs and their progeny and may be useful in strategies for combating neurodegenerative disorders.

    View details for DOI 10.1016/j.jneumeth.2008.06.005

    View details for Web of Science ID 000258906300016

    View details for PubMedID 18606184

  • Neurogenesis and alterations of neural stem cells in mouse models of cerebral amyloidosis AMERICAN JOURNAL OF PATHOLOGY Ermini, F. V., Grathwohl, S., Radde, R., Yamaguchi, M., Staufenbiel, M., Palmer, T. D., Jucker, M. 2008; 172 (6): 1520-1528

    Abstract

    The hippocampus in Alzheimer's disease is burdened with amyloid plaques and is one of the few locations where neurogenesis continues throughout adult life. To evaluate the impact of amyloid-beta deposition on neural stem cells, hippocampal neurogenesis was assessed using bromodeoxyuridine incorporation and doublecortin staining in two amyloid precursor protein (APP) transgenic mouse models. In 5-month-old APP23 mice prior to amyloid deposition, neurogenesis showed no robust difference relative to wild-type control mice, but 25-month-old amyloid-depositing APP23 mice showed significant increases in neurogenesis compared to controls. In contrast, 8-month-old amyloid-depositing APPPS1 mice revealed decreases in neurogenesis compared to controls. To study whether alterations in neurogenesis are the result of amyloid-induced changes at the level of neural stem cells, APPPS1 mice were crossed with mice expressing green fluorescence protein (GFP) under a central nervous system-specific nestin promoter. Eight-month-old nestin-GFP x APPPS1 mice exhibited decreases in quiescent nestin-positive astrocyte-like stem cells, while transient amplifying progenitor cells did not change in number. Strikingly, both astrocyte-like and transient-amplifying progenitor cells revealed an aberrant morphologic reaction toward congophilic amyloid-deposits. A similar reaction toward the amyloid was no longer observed in doublecortin-positive immature neurons. Results provide evidence for a disruption of neural stem cell biology in an amyloidogenic environment and support findings that neurogenesis is differently affected among various transgenic mouse models of Alzheimer's disease.

    View details for DOI 10.2353/ajpath.2008.060520

    View details for Web of Science ID 000256326800010

    View details for PubMedID 18467698

  • Cellular repair of CNS disorders: an immunological perspective HUMAN MOLECULAR GENETICS Chen, Z., Palmer, T. D. 2008; 17: R84-R92

    Abstract

    Cellular repair is a promising strategy for treating central nervous system (CNS) disorders. Several strategies have been contemplated including replacement of neurons or glia that have been lost due to injury or disease, use of cellular grafts to modify or augment the functions of remaining neurons and/or use of cellular grafts to protect neural tissue by local delivery of growth or trophic factors. Depending on the specific disease target, there may be one or many cell types that could be considered for therapy. In each case, an additional variable must be considered--the role of the immune system in both the injury process itself and in the response to incoming cells. Cellular transplants can be roughly categorized into autografts, allografts and xenografts. Despite the immunological privilege of the CNS, allografts and xenografts can elicit activation of the innate and adaptive immune system. In this article, we evaluate the various effects that immune cells and signals may have on the survival, proliferation, differentiation and migration/integration of transplanted cells in therapeutic approaches to CNS injury and disease.

    View details for DOI 10.1093/hmg/ddn104

    View details for Web of Science ID 000258261600014

    View details for PubMedID 18632702

  • Neural progenitor cells transplanted into the uninjured brain undergo targeted migration after stroke onset JOURNAL OF NEUROSCIENCE RESEARCH Guzman, R., Bliss, T., Angeles, A. D., Moseley, M., Palmer, T., Steinberg, G. 2008; 86 (4): 873-882

    Abstract

    Endogenous neural stem cells normally reside in their niche, the subventricular zone, in the uninjured rodent brain. Upon stroke, these cells become more proliferative and migrate away from the subventricular zone into the surrounding parenchyma. It is not known whether this stroke-induced behavior is due to changes in the niche or introduction of attractive cues in the infarct zone, or both. A related question is how transplanted neural stem cells respond to subsequent insults, including whether exogenous stem cells have the plasticity to respond to subsequent injuries after engraftment. We addressed this issue by transplanting neural progenitor cells (NPCs) into the uninjured brain and then subjecting the animal to stroke. We were able to follow the transplanted NPCs in vivo by labeling them with superparamagnetic iron oxide particles and imaging them via high-resolution magnetic resonance imaging (MRI) during engraftment and subsequent to stroke. We find that transplanted NPCs that are latent can be activated in response to stroke and exhibit directional migration into the parenchyma, similar to endogenous neural NPCs, without a niche environment.

    View details for DOI 10.1002/jnr.21542

    View details for Web of Science ID 000253961700013

    View details for PubMedID 17975825

  • Lithium regulates adult hippocampal progenitor development through canonical Wnt pathway activation MOLECULAR PSYCHIATRY Wexler, E. M., Geschwind, D. H., Palmer, T. D. 2008; 13 (3): 285-292

    Abstract

    Neural stem cells give rise to new hippocampal neurons throughout adulthood, and defects in neurogenesis may predispose an individual to mood disorders, such as major depression. Our understanding of the signals controlling this process is limited, so we explored potential pathways regulating adult hippocampal progenitor (AHP) proliferation and neuronal differentiation. We demonstrate that the mood stabilizer lithium directly expands pools of AHPs in vitro, and induces them to become neurons at therapeutically relevant concentrations. We show that these effects are independent of inositol monophosphatase, but dependent on Wnt pathway components. Both downregulation of glycogen synthase kinase-3beta, a lithium-sensitive component of the canonical Wnt signaling pathway, and elevated beta-catenin, a downstream component of the same pathway produce effects similar to lithium. In contrast, RNAi-mediated inhibition of beta-catenin abolishes the proliferative effects of lithium, suggesting that Wnt signal transduction may underlie lithium's therapeutic effect. Together, these data strengthen the connection between psychopharmacologic treatment and the process of adult neurogenesis, while also suggesting the pursuit of modulators of Wnt signaling as a new class of more effective mood stabilizers/antidepressants.

    View details for DOI 10.1038/sj.mp.4002093

    View details for Web of Science ID 000253238600009

    View details for PubMedID 17968353

  • Neurodegeneration and cell replacement PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES Ormerod, B. K., Palmer, T. D., Caldwell, M. A. 2008; 363 (1489): 153-170

    Abstract

    The past decade has witnessed ground-breaking advances in human stem cell biology with scientists validating adult neurogenesis and establishing methods to isolate and propagate stem cell populations suitable for transplantation. These advances have forged promising strategies against human neurodegenerative diseases. For example, growth factor administration could stimulate intrinsic repair from endogenous neural stem cells, and cultured stem cells engineered into biopumps could be transplanted to deliver neuroprotective or restorative agents. Stem cells could also be transplanted to generate new neural elements that augment and potentially replace degenerating central nervous system (CNS) circuitry. Early efforts in neural tissue transplantation have shown that these strategies can improve functional outcome, but the ultimate success of clinical stem cell-based strategies will depend on detailed understanding of stem cell biology in the degenerating brain and detailed evaluation of their functional efficacy and safety in preclinical animal models.

    View details for DOI 10.1098/rstb.2006.2018

    View details for Web of Science ID 000251562600012

    View details for PubMedID 17331894

  • Long-term monitoring of transplanted human neural stem cells in developmental and pathological contexts with MRI PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Guzman, R., Uchida, N., Bliss, T. M., He, D., Christopherson, K. K., Stellwagen, D., Capela, A., Greve, J., Malenka, R. C., Moseley, M. E., Palmer, T. D., Steinberg, G. K. 2007; 104 (24): 10211-10216

    Abstract

    Noninvasive monitoring of stem cells, using high-resolution molecular imaging, will be instrumental to improve clinical neural transplantation strategies. We show that labeling of human central nervous system stem cells grown as neurospheres with magnetic nanoparticles does not adversely affect survival, migration, and differentiation or alter neuronal electrophysiological characteristics. Using MRI, we show that human central nervous system stem cells transplanted either to the neonatal, the adult, or the injured rodent brain respond to cues characteristic for the ambient microenvironment resulting in distinct migration patterns. Nanoparticle-labeled human central nervous system stem cells survive long-term and differentiate in a site-specific manner identical to that seen for transplants of unlabeled cells. We also demonstrate the impact of graft location on cell migration and describe magnetic resonance characteristics of graft cell death and subsequent clearance. Knowledge of migration patterns and implementation of noninvasive stem cell tracking might help to improve the design of future clinical neural stem cell transplantation.

    View details for DOI 10.1073/pnas.0608519104

    View details for Web of Science ID 000247363000053

    View details for PubMedID 17553967

  • Chronically increased transforming growth factor-beta 1 strongly inhibits hippocampal neurogenesis in aged mice AMERICAN JOURNAL OF PATHOLOGY Buckwalter, M. S., Yamane, M., Coleman, B. S., Ormerod, B. K., Chin, J. T., Palmer, T., Wyss-Coray, T. 2006; 169 (1): 154-164

    Abstract

    There is increasing evidence that hippocampal learning correlates strongly with neurogenesis in the adult brain. Increases in neurogenesis after brain injury also correlate with improved outcomes. With aging the capacity to generate new neurons decreases dramatically, both under normal conditions and after injury. How this decrease occurs is not fully understood, but we hypothesized that transforming growth factor (TGF)-beta1, a cell cycle regulator that rapidly increases after injury and with age, might play a role. We found that chronic overproduction of TGF-beta1 from astrocytes almost completely blocked the generation of new neurons in aged transgenic mice. Even young adult TGF-beta1 mice had 60% fewer immature, doublecortin-positive, hippocampal neurons than wild-type littermate controls. Bromodeoxyuridine labeling of dividing cells in 2-month-old TGF-beta1 mice confirmed this decrease in neuro-genesis and revealed a similar decrease in astrogenesis. Treatment of early neural progenitor cells with TGF-beta1 inhibited their proliferation. This strongly suggests that TGF-beta1 directly affects these cells before their differentiation into neurons and astrocytes. Together, these data show that TGF-beta1 is a potent inhibitor of hippocampal neural progenitor cell proliferation in adult mice and suggest that it plays a key role in limiting injury and age-related neurogenesis.

    View details for DOI 10.2353/ajpath.2006.051272

    View details for Web of Science ID 000238664700014

    View details for PubMedID 16816369

  • Transplantation of hNT neurons into the ischemic cortex: Cell survival and effect on sensorimotor behavior JOURNAL OF NEUROSCIENCE RESEARCH Bliss, T. M., Kelly, S., Shah, A. K., Foo, W. C., Kohli, P., Stokes, C., Sun, G. H., Ma, M., Masel, J., Kleppner, S. R., Schallert, T., Palmer, T., Steinberg, G. K. 2006; 83 (6): 1004-1014

    Abstract

    Cell transplantation offers a potential new treatment for stroke. Animal studies using models that produce ischemic damage in both the striatum and the frontal cortex have shown beneficial effects when hNT cells (postmitotic immature neurons) were transplanted into the ischemic striatum. In this study, we investigated the effect of hNT cells in a model of stroke in which the striatum remains intact and damage is restricted to the cortex. hNT cells were transplanted into the ischemic cortex 1 week after stroke induced by distal middle cerebral artery occlusion (dMCAo). The cells exhibited robust survival at 4 weeks posttransplant even at the lesion border. hNT cells did not migrate, but they did extend long neurites into the surrounding parenchyma mainly through the white matter. Neurite extension was predominantly toward the lesion in ischemic animals but was bidirectional in uninjured animals. Extension of neurites through the cortex toward the lesion was also seen when there was some surviving cortical tissue between the graft and the infarct. Prolonged deficits were obtained in four tests of sensory-motor function. hNT-transplanted animals showed a significant improvement in functional recovery on one motor test, but there was no effect on the other three tests relative to control animals. Thus, despite clear evidence of graft survival and neurite extension, the functional benefit of hNT cells after ischemia is not guaranteed. Functional benefit could depend on other variables, such as infarct location, whether the cells mature, the behavioral tests employed, rehabilitation training, or as yet unidentified factors.

    View details for DOI 10.1002/jnr.20800

    View details for Web of Science ID 000237217100008

    View details for PubMedID 16496370

  • Exploring the regulation of human neural precursor cell differentiation using arrays of signaling microenvironments MOLECULAR SYSTEMS BIOLOGY Soen, Y., Mori, A., Palmer, T. D., Brown, P. O. 2006; 2

    Abstract

    Cells of a developing embryo integrate a complex array of local and long-range signals that act in concert with cell-intrinsic determinants to influence developmental decisions. To systematically investigate the effects of molecular microenvironments on cell fate decisions, we developed an experimental method based on parallel exposure of cells to diverse combinations of extracellular signals followed by quantitative, multi-parameter analysis of cellular responses. Primary human neural precursor cells were captured and cultured on printed microenvironment arrays composed of mixtures of extracellular matrix components, morphogens, and other signaling proteins. Quantitative single cell analysis revealed striking effects of some of these signals on the extent and direction of differentiation. We found that Wnt and Notch co-stimulation could maintain the cells in an undifferentiated-like, proliferative state, whereas bone morphogenetic protein 4 induced an 'indeterminate' differentiation phenotype characterized by simultaneous expression of glial and neuronal markers. Multi-parameter analysis of responses to conflicting signals revealed interactions more complex than previously envisaged including dominance relations that may reflect a cell-intrinsic system for robust specification of responses in complex microenvironments.

    View details for DOI 10.1038/msb4100076

    View details for Web of Science ID 000243245400037

    View details for PubMedID 16820778

  • Neurogenesis in rats after focal cerebral ischemia is enhanced by indomethacin STROKE Hoehn, B. D., Palmer, T. D., Steinberg, G. K. 2005; 36 (12): 2718-2724

    Abstract

    Newborn cells may participate in repair following ischemic brain injury, but their survival and function may be influenced by inflammation.We investigated the effects of indomethacin, a nonsteroidal antiinflammatory drug, on the fate of newborn cells following transient focal ischemia.Bromodeoxyuridine (BrdU)-labeled cells, including migrating neuroblasts, were observed in the neighboring striatum and overlying cortex 1 day poststroke. The density of BrdU+ cells labeled with doublecortin, nestin, glial fibrillary acidic protein, or NG2 was increased at 14 and 28 days. Indomethacin increased BrdU+ cells of all lineages and reduced microglial/monocyte activation.Indomethacin enhanced the accumulation of newborn cells following stroke.

    View details for DOI 10.1161/01.STR.0000190020.30282.cc

    View details for Web of Science ID 000233452400047

    View details for PubMedID 16282546

  • Sleep restriction suppresses neurogenesis induced by hippocampus-dependent learning JOURNAL OF NEUROPHYSIOLOGY Hairston, I. S., Little, M. T., Scanlon, M. D., Barakat, M. T., Palmer, T. D., Sapolsky, R. M., Heller, H. C. 2005; 94 (6): 4224-4233

    Abstract

    Sleep deprivation impairs hippocampal-dependent learning, which, in turn, is associated with increased survival of newborn cells in the hippocampus. We tested whether the deleterious effects of sleep restriction on hippocampus-dependent memory were associated with reduced cell survival in the hippocampus. We show that sleep restriction impaired hippocampus-dependent learning and abolished learning-induced neurogenesis. Animals were trained in a water maze on either a spatial learning (hippocampus-dependent) task or a nonspatial (hippocampus-independent) task for 4 days. Sleep-restricted animals were kept awake for one-half of their rest phase on each of the training days. Consistent with previous reports, animals trained on the hippocampus-dependent task expressed increased survival of newborn cells in comparison with animals trained on the hippocampus-independent task. This increase was abolished by sleep restriction that caused overall reduced cell survival in all animals. Sleep restriction also selectively impaired spatial learning while performance in the nonspatial task was, surprisingly, improved. Further analysis showed that in both training groups fully rested animals applied a spatial strategy irrespective of task requirements; this strategy interfered with performance in the nonspatial task. Conversely, in sleep-restricted animals, this preferred spatial strategy was eliminated, favoring the use of nonspatial information, and hence improving performance in the nonspatial task. These findings suggest that sleep loss altered behavioral strategies to those that do not depend on the hippocampus, concomitantly reversing the neurogenic effects of hippocampus-dependent learning.

    View details for DOI 10.1152/jn.00218.2005

    View details for Web of Science ID 000233317100053

    View details for PubMedID 16014798

  • Transplanted human fetal neural stem cells survive, migrate, and differentiate in ischemic rat cerebral cortex PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Kelly, S., Bliss, T. M., Shah, A. K., Sun, G. H., Ma, M., Foo, W. C., Masel, J., Yenari, M. A., Weissman, I. L., Uchida, N., Palmer, T., Steinberg, G. K. 2004; 101 (32): 11839-11844

    Abstract

    We characterize the survival, migration, and differentiation of human neurospheres derived from CNS stem cells transplanted into the ischemic cortex of rats 7 days after distal middle cerebral artery occlusion. Transplanted neurospheres survived robustly in naive and ischemic brains 4 wk posttransplant. Survival was influenced by proximity of the graft to the stroke lesion and was negatively correlated with the number of IB4-positive inflammatory cells. Targeted migration of the human cells was seen in ischemic animals, with many human cells migrating long distances ( approximately 1.2 mm) predominantly toward the lesion; in naive rats, cells migrated radially from the injection site in smaller number and over shorter distances (0.2 mm). The majority of migrating cells in ischemic rats had a neuronal phenotype. Migrating cells between the graft and the lesion expressed the neuroblast marker doublecortin, whereas human cells at the lesion border expressed the immature neuronal marker beta-tubulin, although a small percentage of cells at the lesion border also expressed glial fibrillary acid protein (GFAP). Thus, transplanted human CNS (hCNS)-derived neurospheres survived robustly in naive and ischemic brains, and the microenvironment influenced their migration and fate.

    View details for DOI 10.1073/pnas.0404474101

    View details for Web of Science ID 000223276700056

    View details for PubMedID 15280535

  • Neuroscience. Cellular interactions in the stem cell niche. Science Wurmser, A. E., Palmer, T. D., Gage, F. H. 2004; 304 (5675): 1253-1255

    View details for PubMedID 15166350

  • Excitation-neurogenesis coupling in adult neural stem/progenitor cells NEURON Deisseroth, K., Singla, S., Toda, H., Monje, M., Palmer, T. D., Malenka, R. C. 2004; 42 (4): 535-552

    Abstract

    A wide variety of in vivo manipulations influence neurogenesis in the adult hippocampus. It is not known, however, if adult neural stem/progenitor cells (NPCs) can intrinsically sense excitatory neural activity and thereby implement a direct coupling between excitation and neurogenesis. Moreover, the theoretical significance of activity-dependent neurogenesis in hippocampal-type memory processing networks has not been explored. Here we demonstrate that excitatory stimuli act directly on adult hippocampal NPCs to favor neuron production. The excitation is sensed via Ca(v)1.2/1.3 (L-type) Ca(2+) channels and NMDA receptors on the proliferating precursors. Excitation through this pathway acts to inhibit expression of the glial fate genes Hes1 and Id2 and increase expression of NeuroD, a positive regulator of neuronal differentiation. These activity-sensing properties of the adult NPCs, when applied as an "excitation-neurogenesis coupling rule" within a Hebbian neural network, predict significant advantages for both the temporary storage and the clearance of memories.

    View details for Web of Science ID 000221708300006

    View details for PubMedID 15157417

  • Novel neuronal phenotypes from neural progenitor cells JOURNAL OF NEUROSCIENCE Markakis, E. A., Palmer, T. D., Randolph-Moore, L., RAKIC, P., Gage, F. H. 2004; 24 (12): 2886-2897

    Abstract

    We report the first isolation of progenitor cells from the hypothalamus, a derivative of the embryonic basal plate that does not exhibit neurogenesis postnatally. Neurons derived from hypothalamic progenitor cells were compared with those derived from progenitor cultures of hippocampus, an embryonic alar plate derivative that continues to support neurogenesis in vivo into adulthood. Aside from their different embryonic origins and their different neurogenic potential in vivo, these brain regions were chosen because they are populated with cells of three different categories: Category I cells are generated in both hippocampus and hypothalamus, Category II cells are generated in the hypothalamus but are absent from the hippocampus, and Category III is a cell type generated in the olfactory placode that migrates into the hypothalamus during development. Stem-like cells isolated from other brain regions, with the ability to generate neurons and glia, produce neurons of several phenotypes including gabaergic, dopaminergic, and cholinergic lineages. In the present study, we extended our observations into neuroendocrine phenotypes. The cultured neural precursors from 7-week-old rat hypothalamus readily generated neuropeptide-expressing neurons. Hippocampal and hypothalamic progenitor cultures converged to indistinguishable populations and produced neurons of all three categories, confirming that even short-term culture confers or selects for immature progenitors with enough plasticity to elaborate neuronal phenotypes usually inhibited in vivo by the local microenvironment. The range of phenotypes generated from neuronal precursors in vitro now includes the peptides found in the neuroendocrine system: corticotropin-releasing hormone, growth hormone-releasing hormone, gonadotropin-releasing hormone, oxytocin, somatostatin, thyrotropin-releasing hormone, and vasopressin.

    View details for DOI 10.1523/JNEUROSCI.4161-03.2004

    View details for Web of Science ID 000220500900004

    View details for PubMedID 15044527

  • Radiation response of neural precursor cells: Linking cellular sensitivity to cell cycle checkpoints, apoptosis and oxidative stress RADIATION RESEARCH Limoli, C. L., Giedzinski, E., Rola, R., Otsuka, S., Palmer, T. D., Fike, J. R. 2004; 161 (1): 17-27

    Abstract

    Therapeutic irradiation of the brain can cause a progressive cognitive dysfunction that may involve defects in neurogenesis. In an effort to understand the mechanisms underlying radiation-induced stem cell dysfunction, neural precursor cells isolated from the adult rat hippocampus were analyzed for acute (0-24 h) and chronic (3-33 days) changes in apoptosis and reactive oxygen species (ROS) after exposure to X rays. Irradiated neural precursor cells exhibited an acute dose-dependent apoptosis accompanied by an increase in ROS that persisted over a 3-4-week period. The radiation effects included the activation of cell cycle checkpoints that were associated with increased Trp53 phosphorylation and Trp53 and p21 (Cdkn1a) protein levels. In vivo, neural precursor cells within the hippocampal dentate subgranular zone exhibited significant sensitivity to radiation. Proliferating precursor cells and their progeny (i.e. immature neurons) exhibited dose-dependent reductions in cell number. These reductions were less severe in Trp53-null mice, possibly due to the disruption of apoptosis. These data suggest that the apoptotic and ROS responses may be tied to Trp53-dependent regulation of cell cycle control and stress-activated pathways. The temporal coincidence between in vitro and in vivo measurements of apoptosis suggests that oxidative stress may provide a mechanistic explanation for radiation-induced inhibition of neurogenesis in the development of cognitive impairment.

    View details for Web of Science ID 000187627300003

    View details for PubMedID 14680400

  • Inflammatory blockade restores adult hippocampal neurogenesis SCIENCE Monje, M. L., Toda, H., Palmer, T. D. 2003; 302 (5651): 1760-1765

    Abstract

    Cranial radiation therapy causes a progressive decline in cognitive function that is linked to impaired neurogenesis. Chronic inflammation accompanies radiation injury, suggesting that inflammatory processes may contribute to neural stem cell dysfunction. Here, we show that neuroinflammation alone inhibits neurogenesis and that inflammatory blockade with indomethacin, a common nonsteroidal anti-inflammatory drug, restores neurogenesis after endotoxin-induced inflammation and augments neurogenesis after cranial irradiation.

    View details for Web of Science ID 000186970100047

    View details for PubMedID 14615545

  • New roles for astrocytes: The nightlife of an 'astrocyte'. La vida loca! TRENDS IN NEUROSCIENCES Horner, P. J., Palmer, T. D. 2003; 26 (11): 597-603

    Abstract

    Like a newly popular nightspot, the biology of adult stem cells has emerged from obscurity to become one of the most lively new disciplines of the decade. The neurosciences have not escaped this trendy pastime and, from amid the noise and excitement, the astrocyte emerges as a beguiling companion to the adult neural stem cell. A once receding partner to neurons and oligodendrocytes, the astrocyte even takes on an alter ego of the stem cell itself (S. Goldman, this issue of TINS). Putting ego aside, the 'astrocyte' is also (and perhaps more importantly) an integral component of neural progenitor hotspots, where the craziness or 'la vida loca' of the nightlife might not be so wild when compared with our traditional understanding of the astrocyte. Here, astrocytes contribute to the instructive confluence of location, atmosphere and cellular neighbors that define the daily 'vida local' or everyday local life of an adult stem cell. This review discusses astrocytes as influential components in the local stem cell niche.

    View details for DOI 10.1016/j.tins.2003.09.010

    View details for Web of Science ID 000186452800007

    View details for PubMedID 14585599

  • VEGF is necessary for exercise-induced adult hippocampal neurogenesis EUROPEAN JOURNAL OF NEUROSCIENCE Fabel, K., Fabel, K., Tam, B., Kaufer, D., Baiker, A., Simmons, N., Kuo, C. J., Palmer, T. D. 2003; 18 (10): 2803-2812

    Abstract

    Declining learning and memory function is associated with the attenuation of adult hippocampal neurogenesis. As in humans, chronic stress or depression in animals is accompanied by hippocampal dysfunction, and neurogenesis is correspondingly down regulated, in part, by the activity of the hypothalamic-pituitary-adrenal axis as well as glutamatergic and serotonergic networks. Antidepressants can reverse this effect over time but one of the most clinically effective moderators of stress or depression and robust stimulators of neurogenesis is simple voluntary physical exercise such as running. Curiously, running also elevates circulating stress hormone levels yet neurogenesis is doubled in running animals. In evaluating the signalling that running provides to the central nervous system in mice, we have found that peripheral vascular endothelial growth factor (VEGF) is necessary for the effects of running on adult hippocampal neurogenesis. Peripheral blockade of VEGF abolished running-induced neurogenesis but had no detectable effect on baseline neurogenesis in non-running animals. These data suggest that VEGF is an important element of a 'somatic regulator' of adult neurogenesis and that these somatic signalling networks can function independently of the central regulatory networks that are typically considered in the context of hippocampal neurogenesis.

    View details for DOI 10.1046/j.1460-9568.2003.03041.x

    View details for Web of Science ID 000186799700014

    View details for PubMedID 14656329

  • Stem cell-derived neural stem/progenitor cell supporting factor is an autocrine/paracrine survival factor for adult neural stem/progenitor cells JOURNAL OF BIOLOGICAL CHEMISTRY Toda, H., Tsuji, M., Nakano, I., Kobuke, K., Hayashi, T., Kasahara, H., Takahashi, J., Mizoguchi, A., Houtani, T., Sugimoto, T., Hashimoto, N., Palmer, T. D., Honjo, T., Tashiro, K. 2003; 278 (37): 35491-35500

    Abstract

    Recent evidence suggests that adult neural stem/progenitor cells (ANSCs) secrete autocrine/paracrine factors and that these intrinsic factors are involved in the maintenance of adult neurogenesis. We identified a novel secretory molecule, stem cell-derived neural stem/progenitor cell supporting factor (SDNSF), from adult hippocampal neural stem/progenitor cells by using the signal sequence trap method. The expression of SDNSF in adult central nervous system was localized to hippocampus including dentate gyrus, where the neurogenesis persists throughout life. In induced neurogenesis status seen in ischemically treated hippocampus, the expression of SDNSF was up-regulated. As functional aspects, SDNSF protein provided a dose-dependent survival effect for ANSC following basic fibroblast growth factor 2 (FGF-2) withdrawal. ANSCs treated by SDNSF also retain self-renewal potential and multipotency in the absence of FGF-2. However, SDNSF did not have mitogenic activity, nor was it a cofactor that promoted the mitogenic effects of FGF-2. These data suggested an important role of SDNSF as an autocrine/paracrine factor in maintaining stem cell potential and lifelong neurogenesis in adult central nervous system.

    View details for DOI 10.1074/jbc.M305342200

    View details for Web of Science ID 000185164400091

    View details for PubMedID 12832409

  • IGF-I has a direct proliferative effect in adult hippocampal progenitor cells MOLECULAR AND CELLULAR NEUROSCIENCE Aberg, M. A., Aberg, N. D., Palmer, T. D., Alborn, A. M., Carlsson-Skwirut, C., Bang, P., Rosengren, L. E., Olsson, T., Gage, F. H., Eriksson, P. S. 2003; 24 (1): 23-40

    Abstract

    The aim of the present study was to investigate the potential direct effects of insulin-like growth factor-I (IGF-I) on adult rat hippocampal stem/progenitor cells (AHPs). IGF-I-treated cultures showed a dose-dependent increase in thymidine incorporation, total number of cells, and number of cells entering the mitosis phase. Pretreatment with fibroblast growth factor-2 (FGF-2) increased the IGF-I receptor (IGF-IR) expression, and both FGF-2 and IGF-I were required for maximal proliferation. Time-lapse recordings showed that IGF-I at 100 ng/ml decreased differentiation and increased proliferation of single AHPs. Specific inhibition of mitogen-activated protein kinase kinase (MAPKK), phosphatidylinositol 3-kinase (PI3-K), or the downstream effector of the PI3-K pathway, serine/threonine p70 S6 kinase (p70(S6K)), showed that both the MAPK and the PI3-K pathways participate in IGF-I-induced proliferation but that the MAPK activation is obligatory. These results were confirmed with dominant-negative constructs for these pathways. Stimulation of differentiation was found at a low dose (1 ng/ml) of IGF-I, clonal analysis indicating an instructive component of IGF-I signaling.

    View details for DOI 10.1016/S1044-7431(03)00082-4

    View details for Web of Science ID 000185796500003

    View details for PubMedID 14550766

  • Extreme sensitivity of adult neurogenesis to low doses of X-irradiation CANCER RESEARCH Mizumatsu, S., Monje, M. L., Morhardt, D. R., Rola, R., Palmer, T. D., Fike, J. R. 2003; 63 (14): 4021-4027

    Abstract

    Therapeutic irradiation of the brain is associated with a number of adverse effects, including cognitive impairment. Although the pathogenesis of radiation-induced cognitive injury is unknown, it may involve loss of neural precursor cells from the subgranular zone (SGZ) of the hippocampal dentate gyrus and alterations in new cell production (neurogenesis). Young adult male C57BL mice received whole brain irradiation, and 6-48 h later, hippocampal tissue was assessed using immunohistochemistry for detection of apoptosis and numbers of proliferating cells and immature neurons. Apoptosis peaked 12 h after irradiation, and its extent was dose dependent. Forty-eight h after irradiation, proliferating SGZ cells were reduced by 93-96%; immature neurons were decreased from 40 to 60% in a dose-dependent fashion. To determine whether acute cell sensitivity translated into long-term changes, we quantified neurogenesis 2 months after irradiation with 0, 2, 5, or 10 Gy. Multiple injections of BrdUrd were given to label proliferating cells, and 3 weeks later, confocal microscopy was used to determine the percentage of BrdUrd-labeled cells that showed mature cell phenotypes. The production of new neurons was significantly reduced by X-rays; that change was dose dependent. In contrast, there were no apparent effects on the production of new astrocytes or oligodendrocytes. Measures of activated microglia indicated that changes in neurogenesis were associated with a significant inflammatory response. Given the known effects of radiation on cognitive function and the relationship between hippocampal neurogenesis and associated memory formation, our data suggest that precursor cell radiation response and altered neurogenesis may play a contributory if not causative role in radiation-induced cognitive impairment.

    View details for Web of Science ID 000184379800031

    View details for PubMedID 12874001

  • Radiation injury and neurogenesis CURRENT OPINION IN NEUROLOGY Monje, M. L., Palmer, T. 2003; 16 (2): 129-134

    Abstract

    For many cancers, survival depends on aggressive combined therapies, but treatment comes at a price. Children and adults who receive radiotherapy involving the brain frequently experience a progressive cognitive decline. The overt pathologies of radiation injury such as white matter necrosis or vasculopathy are the obvious "smoking guns" of dysfunction. However, many patients exhibit severe learning and memory deficits with no overt pathologic changes. This is especially true when the radiation field involves the temporal lobes. The cause of this debilitating dysfunction is currently unknown and untreatable.Within the temporal lobe, the hippocampal formation plays a central role in short-term learning and memory--the functions most notably affected by radiation. Recent work has also shown that hippocampus-dependent learning and memory are strongly influenced by the activity of neural stem cells and their proliferative progeny. The hippocampal granule cell layer undergoes continuous renewal and restructuring by the addition of new neurons. Radiation at much lower doses than that needed to injure the more resistant post-mitotic neurons and glia of the brain has been found to affect these highly proliferative progenitors severely. The stem/progenitor cell is so sensitive to radiation that a single low dose to the cranium of a mature rat is sufficient to ablate hippocampal neurogenesis.Progressive learning and memory deficits following irradiation may be caused by the accumulating hippocampal dysfunction that results from a long-term absence of normal stem/progenitor activity. Here, the authors describe the nature of this stem cell dysfunction and contemplate how restoration of stem/progenitor cell activity might be approached in experimental models and, eventually, the clinic.

    View details for DOI 10.1097/01.wco.0000063772.8181.b7

    View details for Web of Science ID 000182542200002

    View details for PubMedID 12644738

  • Copernican stem cells: Regulatory constellations in adult hippocampal neurogenesis JOURNAL OF CELLULAR BIOCHEMISTRY Fabel, K., Toda, H., Fabel, K., Palmer, T. 2003; 88 (1): 41-50

    Abstract

    In the adult, neurogenesis occurs where constellations of signaling molecules are correctly orchestrated and where competent cells are present to interpret these signals. As the instruments used to observe adult neurogenesis become more sophisticated, the concept of a discrete competent "stem cell" has become less concrete. Neural progenitor cells once thought committed to a single lineage can be influenced to become multipotent and somatic tissues appear to yield cells capable of tremendous peripheral and central lineage potential. The variety of cell types that appear competent to generate neurons suggests that the "Hilios" of adult neurogenesis may not necessarily be a single cellular entity but rather the sum of signals that dictate, "Make a new neuron here." These signals may not be limited to the recruitment of preexisting neural stem cells but may also, in some subtle way, reprogram local precursors to create "stem-like cells," where needed.

    View details for DOI 10.1002/jcb.10377

    View details for Web of Science ID 000180029700008

    View details for PubMedID 12461773

  • Irradiation induces neural precursor-cell dysfunction NATURE MEDICINE Monje, M. L., Mizumatsu, S., Fike, J. R., Palmer, T. D. 2002; 8 (9): 955-962

    Abstract

    In both pediatric and adult patients, cranial radiation therapy causes a debilitating cognitive decline that is poorly understood and currently untreatable. This decline is characterized by hippocampal dysfunction, and seems to involve a radiation-induced decrease in postnatal hippocampal neurogenesis. Here we show that the deficit in neurogenesis reflects alterations in the microenvironment that regulates progenitor-cell fate, as well as a defect in the proliferative capacity of the neural progenitor-cell population. Not only is hippocampal neurogenesis ablated, but the remaining neural precursors adopt glial fates and transplants of non-irradiated neural precursor cells fail to differentiate into neurons in the irradiated hippocampus. The inhibition of neurogenesis is accompanied by marked alterations in the neurogenic microenvironment, including disruption of the microvascular angiogenesis associated with adult neurogenesis and a marked increase in the number and activation status of microglia within the neurogenic zone. These findings provide clear targets for future therapeutic interventions.

    View details for DOI 10.1038/nm749

    View details for Web of Science ID 000177757900030

    View details for PubMedID 12161748

  • Adult neurogenesis and the vascular Nietzsche NEURON Palmer, T. D. 2002; 34 (6): 856-858

    Abstract

    Adult neurogenesis is mediated by immature neural precursors that divide within the residual germinal matrices of the brain. In the paper by in this issue of Neuron, the "cause and effect" of adult neurogenesis takes a major step forward with the description of a vascular signaling network that influences neuronal precursor migration and fate.

    View details for Web of Science ID 000176249700003

    View details for PubMedID 12086632

  • Where, oh where, have my stem cells gone? TRENDS IN NEUROSCIENCES Wexler, E., Palmer, T. 2002; 25 (5): 225-227

    Abstract

    During the summer of 2001, Americans were treated to high political drama courtesy of the debate over embryonic and adult stem cell research. The popular press was flush with predictions about how neural stem cells would reverse, almost by magic, the devastation caused by diseases such as Alzheimer's, Parkinson's, stroke or spinal cord injury. Unfortunately, this promise remains unfulfilled because we have such a poor understanding of how stem cells function. With regard to adult stem cells, we are not even completely sure where they are, or how or when they got there. A provocative study by Ourednik et al. published in Science suggests that in primates, adult neural stem cells are allocated during early corticogenesis. The study also provides evidence for the existence of stem cells dispersed throughout the frontal cortex and striatum.

    View details for Web of Science ID 000175141300002

    View details for PubMedID 11972951

  • Functional neurogenesis in the adult hippocampus NATURE van Praag, H., Schinder, A. F., Christie, B. R., Toni, N., Palmer, T. D., Gage, F. H. 2002; 415 (6875): 1030-1034

    Abstract

    There is extensive evidence indicating that new neurons are generated in the dentate gyrus of the adult mammalian hippocampus, a region of the brain that is important for learning and memory. However, it is not known whether these new neurons become functional, as the methods used to study adult neurogenesis are limited to fixed tissue. We use here a retroviral vector expressing green fluorescent protein that only labels dividing cells, and that can be visualized in live hippocampal slices. We report that newly generated cells in the adult mouse hippocampus have neuronal morphology and can display passive membrane properties, action potentials and functional synaptic inputs similar to those found in mature dentate granule cells. Our findings demonstrate that newly generated cells mature into functional neurons in the adult mammalian brain.

    View details for Web of Science ID 000174075000047

    View details for PubMedID 11875571

  • Expression of IL-17B in neurons and evaluation of its possible role in the chromosome 5q-linked form of Charcot-Marie-Tooth disease NEUROMUSCULAR DISORDERS Moore, E. E., Presnell, S., Garrigues, U., Guilbot, A., LeGuern, E., Smith, D., Yao, L., Whitmore, T. E., Gilbert, T., Palmer, T. D., Horner, P. J., Kuestner, R. E. 2002; 12 (2): 141-150

    Abstract

    IL-17B is a recently identified homolog of IL-17. Northern analysis revealed that IL-17B mRNA is expressed at very high levels in spinal cord and at much lower and more variable levels in trachea, prostate, lung, small intestine, testes, adrenal, and pancreas. In developing mouse embryos IL-17B expression was first detected at day 11 and appeared to peak at day 15. In situ analysis of mouse spinal cord, dorsal root ganglia, and brain demonstrated that IL-17B mRNA is primarily expressed by the neurons. Immunohistochemical analysis of human spinal cord, dorsal root ganglia, cerebral cortex, cerebellum, and hippocampus demonstrated that IL-17B protein is primarily localized to the neuronal cell bodies and axons. Radiation hybrid mapping localized the IL-17B gene to a region on human chromosome 5q that is associated with a rare autosomal recessive form of Charcot-Marie-Tooth demyelinating disease. However, no changes were found in the coding regions, splice junctions, intron 1, or the 5' and 3' untranslated regions of IL-17B genes of patients affected with this disease.

    View details for Web of Science ID 000173055200006

    View details for PubMedID 11738356

  • Adult neurogenesis: a compensatory mechanism for neuronal damage EUROPEAN ARCHIVES OF PSYCHIATRY AND CLINICAL NEUROSCIENCE Kuhn, H. G., Palmer, T. D., Fuchs, E. 2001; 251 (4): 152-158

    Abstract

    It is now evident that the adult vertebrate brain including the human brain is efficiently and continuously generating new neurons. In the first part we describe the current view of how neurons are generated in the adult brain and the possible compensatory reactions to pathological situations in which neuronal damage might stimulate neural stem cell activity. In the second part, we discuss the current knowledge on the signals and cells involved in the process of neurogenesis. This knowledge is important because any neuronal replacement strategy depends on our ability to induce or modulate each step on the way to a new neuron: stem cell proliferation, cell fate determination, progenitor migration, and differentiation into specific neuronal phenotypes. Identification of the molecular signals that control these events are essential for the application of neural stem cell biology to develop repair strategies for neurodegenerative disorders.

    View details for Web of Science ID 000171591100002

    View details for PubMedID 11697579

  • Cell culture - Progenitor cells from human brain after death NATURE Palmer, T. D., Schwartz, P. H., Taupin, P., Kaspar, B., Stein, S. A., Gage, F. H. 2001; 411 (6833): 42-43

    View details for Web of Science ID 000168432800034

    View details for PubMedID 11333968

  • Vascular niche for adult hippocampal neurogenesis JOURNAL OF COMPARATIVE NEUROLOGY Palmer, T. D., Willhoite, A. R., Gage, F. H. 2000; 425 (4): 479-494

    Abstract

    The thin lamina between the hippocampal hilus and granule cell layer, or subgranule zone (SGZ), is an area of active proliferation within the adult hippocampus known to generate new neurons throughout adult life. Although the neuronal fate of many dividing cells is well documented, little information is available about the phenotypes of cells in S-phase or how the dividing cells might interact with neighboring cells in the process of neurogenesis. Here, we make the unexpected observation that dividing cells are found in dense clusters associated with the vasculature and roughly 37% of all dividing cells are immunoreactive for endothelial markers. Most of the newborn endothelial cells disappear over several weeks, suggesting that neurogenesis is intimately associated with a process of active vascular recruitment and subsequent remodeling. The present data provide the first evidence that adult neurogenesis occurs within an angiogenic niche. This environment may provide a novel interface where mesenchyme-derived cells and circulating factors influence plasticity in the adult central nervous system.

    View details for Web of Science ID 000089056200002

    View details for PubMedID 10975875

  • Proliferation and differentiation of progenitor cells throughout the intact adult rat spinal cord JOURNAL OF NEUROSCIENCE Horner, P. J., Power, A. E., Kempermann, G., Kuhn, H. G., Palmer, T. D., Winkler, J., Thal, L. J., Gage, F. H. 2000; 20 (6): 2218-2228

    Abstract

    The existence of multipotent progenitor populations in the adult forebrain has been widely studied. To extend this knowledge to the adult spinal cord we have examined the proliferation, distribution, and phenotypic fate of dividing cells in the adult rat spinal cord. Bromodeoxyuridine (BrdU) was used to label dividing cells in 13- to 14-week-old, intact Fischer rats. Single daily injections of BrdU were administered over a 12 d period. Animals were killed either 1 d or 4 weeks after the last injection of BrdU. We observed frequent cell division throughout the adult rodent spinal cord, particularly in white matter tracts (5-7% of all nuclei). The majority of BrdU-labeled cells colocalized with markers of immature glial cells. At 4 weeks, 10% of dividing cells expressed mature astrocyte and oligodendroglial markers. These data predict that 0.75% of all astrocytes and 0.82% of all oligodendrocytes are derived from a dividing population over a 4 week period. To determine the migratory nature of dividing cells, a single BrdU injection was given to animals that were killed 1 hr after the injection. In these tissues, the distribution and incidence of BrdU labeling matched those of the 4 week post injection (pi) groups, suggesting that proliferating cells divide in situ rather than migrate from the ependymal zone. These data suggest a higher level of cellular plasticity for the intact spinal cord than has previously been observed and that glial progenitors exist in the outer circumference of the spinal cord that can give rise to both astrocytes and oligodendrocytes.

    View details for Web of Science ID 000085724200021

    View details for PubMedID 10704497

  • The search for neural progenitor cells: prospects for the therapy of neurodegenerative disease MOLECULAR MEDICINE TODAY Shihabuddin, L. S., Palmer, T. D., Gage, F. H. 1999; 5 (11): 474-480

    Abstract

    The etiology of many neurodegenerative diseases has been identified in recent years. Treatment of central nervous system (CNS) disease could focus on one or more steps that lead to cell loss. In the past decade, cell therapy and/or ex vivo gene therapy have emerged as possible strategies for the treatment of neurodegenerative diseases. The ability to grow CNS-derived neural progenitor cells using growth factors has been extremely useful to study diverse phenomena including lineage choice, commitment and differentiation. By virtue of their biological properties and their presence in the adult CNS, neural progenitors represent good candidates for multiple cell-based therapies for neural diseases. Further identification of the molecules that direct the differentiation of adult neural progenitors may allow their activation in vivo to induce self-repair. This review addresses the nature, distribution and regulation of neural stem cells and the potential for applying these cells to both structural CNS repair and gene therapy.

    View details for Web of Science ID 000083258900006

    View details for PubMedID 10529788

  • Fibroblast growth factor-2 activates a latent neurogenic program in neural stem cells from diverse regions of the adult CNS JOURNAL OF NEUROSCIENCE Palmer, T. D., Markakis, E. A., Willhoite, A. R., Safar, F., Gage, F. H. 1999; 19 (19): 8487-8497

    Abstract

    During development of the mammalian brain, both neurons and glia are generated from multipotent neural stem cells. Although neurogenesis ceases in most areas at birth, stem cells continue to generate neurons within the subventricular zone and hippocampal dentate gyrus throughout adult life. In this work, we provide the first demonstration that precursors native to regions of the adult brain that generate only glia can also generate neurons after exposure to FGF-2 in vitro. When progenitors isolated from hippocampal tissue were directly compared with cells isolated from the neocortex, both populations were able to initiate a program of proliferative neurogenesis. Genetic marking and lineage analysis showed that a majority of the cells able to generate neurons were multipotent precursors; however, progeny from these precursors acquired the competence to differentiate into neurons only after exposure to FGF-2. The recruitment of similar FGF-2-responsive cells from the adult optic nerve, a structure well isolated from the neurogenic zones within the brain, confirmed that neuron-competent precursors naturally exist in widely divergent tissues of the adult brain.

    View details for Web of Science ID 000082805400036

    View details for PubMedID 10493749

  • Nurr1, an orphan nuclear receptor, is a transcriptional activator of endogenous tyrosine hydroxylase in neural progenitor cells derived from the adult brain DEVELOPMENT Sakurada, K., Ohshima-Sakurada, M., Palmer, T. D., Gage, F. H. 1999; 126 (18): 4017-4026

    Abstract

    Adult rat-derived hippocampal progenitor cells express many of the molecules implicated in midbrain dopaminergic determination, including FGF receptors 1, 2 and 3, the sonic hedgehog receptor components Smo and Ptc, and the region-specific transcription factors Ptx3 and Nurr1. Here we use undifferentiated progenitors to probe the events leading to the dopaminergic phenotype and find that the influences of Nurr1 can be temporally and mechanistically uncoupled from the patterning influences of sonic hedgehog and FGF-8 or the more generic process of neuronal differentiation itself. In gain-of-function experiments, Nurr1 is able to activate transcription of the tyrosine hydroxylase gene by binding a response element within a region of the tyrosine hydroxylase promoter necessary for midbrain-specific expression. This activation is mediated through a retinoid X receptor independent mechanism and occurs in all precursors, regardless of differentiation status. Overexpression of Nurr1 does not affect proliferation or stimulate neuronal differentiation and has no influence on the expression of other dopaminergic markers. This uncoupling of tyrosine hydroxylase expression from other dopaminergic markers suggests that the midbrain dopaminergic identity is dictated by a combination of pan-dopaminergic (e.g., Shh/FGF-8) and region-specific (Nurr1) mechanisms.

    View details for Web of Science ID 000082965700005

    View details for PubMedID 10457011

  • Retinoic acid and neurotrophins collaborate to regulate neurogenesis in adult-derived neural stem cell cultures JOURNAL OF NEUROBIOLOGY Takahashi, J., Palmer, T. D., Gage, F. H. 1999; 38 (1): 65-81

    Abstract

    The adult rat hippocampus contains fibroblast growth factor 2-responsive stem cells that are self-renewing and have the ability to generate both neurons and glia in vitro, but little is known about the molecular events that regulate stem cell differentiation. Hippocampus-derived stem cell clones were used to examine the effects of retinoic acid (RA) on neuronal differentiation. Exposure to RA caused an immediate up-regulation of NeuroD, increased p21 expression, and concurrent exit from cell cycle. These changes were accompanied by a threefold increase in the number of cells differentiating into immature neurons. An accompanying effect of RA was to sustain or up-regulate trkA, trkB, trkC, and p75NGFR expression. Without RA treatment, cells were minimally responsive to neurotrophins (NTs), whereas the sequential application of RA followed by brain-derived neurotrophic factor or NT-3 led to a significant increase in neurons displaying mature y-a-minobutyric acid, acetylcholinesterase, tyrosine hydroxylase, or calbindin phenotypes. Although NTs promoted maturation, they had little effect on the total number of neurons generated, suggesting that RA and neurotrophins acted at distinct stages in neurogenesis. RA first promoted the acquisition of a neuronal fate, and NTs subsequently enhanced maturation by way of RA-dependent expression of the Trk receptors. In combination, these sequential effects were sufficient to stimulate stem cell-derived progenitors to differentiate into neurons displaying a variety of transmitter phenotypes.

    View details for Web of Science ID 000077781100005

    View details for PubMedID 10027563

  • Widespread integration and survival of adult-derived neural progenitor cells in the developing optic retina MOLECULAR AND CELLULAR NEUROSCIENCE Takahashi, M., Palmer, T. D., Takahashi, J., Gage, F. H. 1998; 12 (6): 340-348

    Abstract

    Adult rat hippocampus-derived neural progenitor cells (AHPC) show considerable adaptability following grafting to several brain regions. To evaluate the plasticity of AHPCs within the optic retina, retrovirally engineered AHPCs were grafted into the vitreous cavity of the adult and newborn rat eye. Within the adult eye, AHPCs formed a uniform nondisruptive lamina in intimate contact with the inner limiting membrane. Within 4 weeks of grafting to the developing eye, the AHPCs were well integrated into the retina and adopted the morphologies and positions of Müller, amacrine, bipolar, horizontal, photoreceptor, and astroglial cells. Although the cells expressed neuronal or glial markers, none acquired end-stage markers unique to retinal neurons. This suggests that the adult-derived stem cells can adapt to a wide variety of heterologous environments and express some but not all features of retinal cells when exposed to the cues present late in retinal development.

    View details for Web of Science ID 000078148200002

    View details for PubMedID 9888988

  • Multipotent progenitor cells in the adult dentate gyrus JOURNAL OF NEUROBIOLOGY Gage, F. H., Kempermann, G., Palmer, T. D., Peterson, D. A., Ray, J. 1998; 36 (2): 249-266

    Abstract

    Neurogenesis persists in the adult dentate gyrus of rodents throughout the life of the organism. The factors regulating proliferation, survival, migration, and differentiation of neuronal progenitors are now being elucidated. Cells from the adult hippocampus can be propagated, cloned in vitro, and induced to differentiate into neurons and glial cells. Cells cultured from the adult rodent hippocampus can be genetically marked and transplanted back to the adult brain, where they survive and differentiate into mature neurons and glial cells. Although multipotent stem cells exist in the adult rodent dentate gyrus, their biological significance remains elusive.

    View details for Web of Science ID 000075117100011

    View details for PubMedID 9712308

  • The adult rat hippocampus contains primordial neural stem cells MOLECULAR AND CELLULAR NEUROSCIENCE Palmer, T. D., Takahashi, J., Gage, F. H. 1997; 8 (6): 389-404

    Abstract

    Adult-derived hippocampal progenitors generate neurons, astrocytes, and oligodendrocytes in vitro and following grafting into the adult brain. Although these progenitors have a considerable capacity for in vitro self renewal, it is not known if each lineage is generated by separate committed precursors or by multipotent stem cells. By genetic marking, we have followed individual cells through the process of proliferative expansion, commitment, and differentiation. All three lineages are generated by single marked cells and the relative proportions of each lineage can be strongly influenced by environmental cues. Differentiation is accompanied by a characteristic progression of lineage-specific markers and can be potentiated by retinoic acid, elevated cyclic AMP, or neurotrophic factors. The ability to genetically mark and clone normal diploid hippocampal progenitors provides the first definitive evidence that multipotent neural stem cells exist outside of the adult striatal subventricular zone and supports the hypothesis that FGF-2-responsive neural stem cells may be broadly distributed in the adult brain.

    View details for Web of Science ID A1997WU79100002

    View details for PubMedID 9143557

  • SURVIVAL AND DIFFERENTIATION OF ADULT NEURONAL PROGENITOR CELLS TRANSPLANTED TO THE ADULT BRAIN PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Gage, F. H., Coates, P. W., Palmer, T. D., Kuhn, H. G., FISHER, L. J., SUHONEN, J. O., Peterson, D. A., Suhr, S. T., Ray, J. 1995; 92 (25): 11879-11883

    Abstract

    The dentate gyrus of the hippocampus is one of the few areas of the adult brain that undergoes neurogenesis. In the present study, cells capable of proliferation and neurogenesis were isolated and cultured from the adult rat hippocampus. In defined medium containing basic fibroblast growth factor (FGF-2), cells can survive, proliferate, and express neuronal and glial markers. Cells have been maintained in culture for 1 year through multiple passages. These cultured adult cells were labeled in vitro with bromodeoxyuridine and adenovirus expressing beta-galactosidase and were transplanted to the adult rat hippocampus. Surviving cells were evident through 3 months postimplantation with no evidence of tumor formation. Within 2 months postgrafting, labeled cells were found in the dentate gyrus, where they differentiated into neurons only in the intact region of the granule cell layer. Our results indicate that FGF-2 responsive progenitors can be isolated from the adult hippocampus and that these cells retain the capacity to generate mature neurons when grafted into the adult rat brain.

    View details for Web of Science ID A1995TJ22200115

    View details for PubMedID 8524867

  • FGF-2-RESPONSIVE NEURONAL PROGENITORS RESIDE IN PROLIFERATIVE AND QUIESCENT REGIONS OF THE ADULT RODENT BRAIN MOLECULAR AND CELLULAR NEUROSCIENCE Palmer, T. D., Ray, J., Gage, F. H. 1995; 6 (5): 474-486

    Abstract

    Neurogenesis is restricted to discrete germinal zones within the developing and the adult central nervous systems. With few exceptions, cells that migrate away from these zones and into the parenchyma no longer participate in the generation of new neurons. In this work, we have found that basic fibroblast growth factor is able to stimulate the proliferation of neuronal and glial progenitors isolated from the septum and striatum of adult rats. These progenitors are indistinguishable from those isolated from the adult hippocampus and subventricular zone, two regions that generate neurons well into adult life. Although a variety of cell types are initially isolated from each brain region, the progenitor-like cells from all four regions are capable of considerable proliferation and, with limited serial passage, can be cultured as enriched populations of immature cells that are capable of differentiating into mature glia and neurons following density arrest and growth factor withdrawal. The fact that cells isolated from the septum and striatum proliferate and have the ability to differentiate into neurons once they are removed from their local environment indicates that neurogenesis may be restricted to discrete areas of the developing and the adult brain by regional differences in regulatory signals rather than from an absence of progenitors capable of responding to neurogenic cues.

    View details for Web of Science ID A1995TD44000006

    View details for PubMedID 8581317

  • EFFICIENT EXPRESSION OF A PROTEIN-CODING GENE UNDER THE CONTROL OF AN RNA POLYMERASE-I PROMOTER NUCLEIC ACIDS RESEARCH Palmer, T. D., Miller, A. D., Reeder, R. H., McStay, B. 1993; 21 (15): 3451-3457

    Abstract

    In mammalian cells, RNA polymerase I transcripts are uncapped and retain a polyphosphate 5' terminus. It is probably for this reason that they are poorly translated as messenger RNA. We show in this report that insertion of an Internal Ribosome Entry Site (IRES) into the 5' leader of an RNA polymerase I transcript overcomes the block to translation, presumably by substituting for the 5' trimethyl G cap. Addition of an SV40 polyA addition signal also enhances protein production from the RNA polymerase I transcript. RNA Polymerase I driven expression vectors containing both elements produce protein at levels comparable to that produced from RNA polymerase II driven expression vectors which utilize a retroviral LTR. RNA Polymerase I driven expression vectors may have a variety of uses both for basic research and for practical expression of recombinant proteins.

    View details for Web of Science ID A1993LQ08300016

    View details for PubMedID 8393988

  • HIGH-LEVEL HUMAN ADENOSINE-DEAMINASE EXPRESSION IN DOG SKIN FIBROBLASTS IS NOT SUSTAINED FOLLOWING TRANSPLANTATION HUMAN GENE THERAPY Ramesh, N., Lau, S., Palmer, T. D., STORB, R., Osborne, W. R. 1993; 4 (1): 3-7

    Abstract

    Primary skin fibroblasts are an attractive target tissue for retroviral-mediated gene therapy; however, transient expression of therapeutic genes has been a recurrent problem in several rodent models. The gradual decrease in gene expression could be tissue or species specific. To investigate the phenomenon further, human adenosine deaminase (ADA) expression was monitored in genetically modified skin fibroblasts transplanted in beagle dogs. In culture, transduced canine fibroblasts expressed high levels of human ADA activity (33.6 mumoles adenosine metabolized per hour per milligram of soluble protein) in comparison to canine ADA in untreated control cells (1.3 mumol/hr.mg protein) and for 2 weeks following transplantation, the graft contained up to four-fold more enzyme activity from human ADA than the endogenous canine enzyme. However, by 10 weeks, human ADA expression was undetectable. At the time when human ADA expression was greatly reduced, DNA analysis showed the presence of vector sequences. These results directly parallel those observed in rodent models and suggest retroviral vector inactivation is a tissue-specific rather than species-specific mechanism.

    View details for Web of Science ID A1993KP28800002

    View details for PubMedID 8461381

  • GENETICALLY MODIFIED SKIN FIBROBLASTS PERSIST LONG AFTER TRANSPLANTATION BUT GRADUALLY INACTIVATE INTRODUCED GENES PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Palmer, T. D., Rosman, G. J., Osborne, W. R., Miller, A. D. 1991; 88 (4): 1330-1334

    Abstract

    Genetically engineered fibroblasts have been successfully used to produce therapeutic proteins in animals, but sustained production of the proteins has not been achieved. This limits the potential of fibroblast-mediated gene therapy in humans. We have studied the phenomenon of decreased production in rats by using retroviral vectors carrying genes encoding human adenosine deaminase and neomycin phosphotransferase. While transplanted skin fibroblasts containing vector sequences persisted at constant levels for at least 8.5 mo, vector expression decreased by greater than 1500-fold after 1 mo. Cellular or antibody-mediated immune responses were not detected in transplanted animals, and expression could not be restored in fibroblasts recultivated from the grafts. This phenomenon is reminiscent of sequence-specific gene inactivation observed in other cell types. Because genetic manipulation and expression of foreign proteins did not affect survival of the transplanted cells, effective long-term therapy may be possible with the use of alternative gene regulatory elements.

    View details for Web of Science ID A1991EY61700051

    View details for PubMedID 1847517

  • Gene transfer as an approach to cure patients with hemophilia A or B. Current studies in hematology and blood transfusion Thompson, A. R., Palmer, T. D., Lynch, C. M., Miller, A. D. 1991: 59-62

    View details for PubMedID 1954775

  • PRODUCTION OF HUMAN FACTOR-IX IN ANIMALS BY GENETICALLY MODIFIED SKIN FIBROBLASTS - POTENTIAL THERAPY FOR HEMOPHILIA-B BLOOD Palmer, T. D., Thompson, A. R., Miller, A. D. 1989; 73 (2): 438-445

    Abstract

    Inherited diseases might be treated by introducing normal genes into a patient's somatic tissues to correct the genetic defects. In the case of hemophilia resulting from a missing clotting factor, the required gene could be introduced into any cell as long as active factor reached the circulation. We previously showed that retroviral vectors can efficiently transfer genes into normal skin fibroblasts and that the infected cells can produce high levels of a therapeutic product in vitro. In the current study, we examined the ability of skin fibroblasts to secrete active clotting factor after infection with different retroviral vectors encoding human clotting factor IX. Normal human fibroblasts infected with one vector secreted greater than 3 micrograms factor IX/10(6) cells/24 h. Of this protein, greater than 70% was structurally and functionally indistinguishable from human factor IX derived from normal plasma. This suggests that infected autologous fibroblasts might provide therapeutic levels of factor IX if transplanted into patients suffering from hemophilia B. By transplanting normal diploid fibroblasts infected with the factor IX vectors, we showed that human factor IX can be produced and is circulated at readily detectable levels in rats and mice.

    View details for Web of Science ID A1989T128400015

    View details for PubMedID 2917183

  • EVIDENCE THAT THE PACKAGING SIGNAL OF MOLONEY MURINE LEUKEMIA-VIRUS EXTENDS INTO THE GAG REGION JOURNAL OF VIROLOGY Bender, M. A., Palmer, T. D., Gelinas, R. E., Miller, A. D. 1987; 61 (5): 1639-1646

    Abstract

    Replication-competent retroviruses can be modified to carry nonviral genes. Such gene transfer vectors help define regions of the retroviral genome that are required in cis for retroviral replication. Moloney murine leukemia virus has been used extensively in vector construction, and all of the internal protein-encoding regions can be removed and replaced with other genes while still allowing production of virions containing and transmitting the altered retroviral genome. However, inclusion of a portion of the gag region from Moloney murine leukemia virus markedly increases the titer of virus derived from these vectors. We determined that this effect was due to more efficient packaging of the vector RNA into particles and did not depend on protein synthesis from the gag region. We conclude that the retrovirus packaging signal extends into the gag region. We have found that retroviral vectors containing the complete packaging signal allow more efficient gene transfer into a variety of cell types. In addition, these results may help explain why many oncogenic retroviruses have retained gag sequences and often express transforming proteins that are gag-onc hybrids.

    View details for Web of Science ID A1987G923200044

    View details for PubMedID 3502707

  • EFFICIENT RETROVIRUS-MEDIATED TRANSFER AND EXPRESSION OF A HUMAN ADENOSINE-DEAMINASE GENE IN DIPLOID SKIN FIBROBLASTS FROM AN ADENOSINE DEAMINASE-DEFICIENT HUMAN PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Palmer, T. D., Hock, R. A., Osborne, W. R., Miller, A. D. 1987; 84 (4): 1055-1059

    Abstract

    Skin fibroblasts might be considered suitable recipients for therapeutic genes to cure several human genetic diseases; however, these cells are resistant to gene transfer by most methods. We have studied the ability of retroviral vectors to transfer genes into normal human diploid skin fibroblasts. Retroviruses carrying genes for neomycin or hygromycin B resistance conferred drug resistance to greater than 50% of the human fibroblasts after a single exposure to virus-containing medium. This represents at least a 500-fold increase in efficiency over other methods. Transfer was achieved in the absence of helper virus by using amphotropic retrovirus-packaging cells. A retrovirus vector containing a human adenosine deaminase (ADA) cDNA was constructed and used to infect ADA-fibroblasts from a patient with ADA deficiency. The infected cells produced 12-fold more ADA enzyme than fibroblasts from normal individuals and were able to rapidly metabolize exogenous deoxyadenosine and adenosine, metabolites that accumulate in plasma in ADA-deficient patients and are responsible for the severe combined immunodeficiency in these patients. These experiments indicate the potential of retrovirus-mediated gene transfer into human fibroblasts for gene therapy.

    View details for Web of Science ID A1987G228000034

    View details for PubMedID 3493485

  • TRANSFER OF GENES INTO HUMAN SOMATIC-CELLS USING RETROVIRUS VECTORS COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY Miller, A. D., Palmer, T. D., Hock, R. A. 1986; 51: 1013-1019

    View details for Web of Science ID A1986H050100034

    View details for PubMedID 3034492

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