Dr. Jacinda Sampson received her MD and a PhD in biochemistry from University of Alabama at Birmingham, and completed her neurology residency and neurogenetics fellowship at the University of Utah. She served at Columbia University Medical Center prior to joining Stanford University Medical Center in 2015. Her areas of interest include myotonic dystrophies, Duchenne muscular dystrophy, and neurogenetic disorders such as neurofibromatosis, hereditary spastic paraparesis, spinocerebellar ataxia, among others. She is interested in clinical trials for treatment of neurogenetic disorders, and is the clinical application of next-generation genomic sequencing to genetic testing.

Clinical Focus

  • Neurology
  • Neurogenetics

Academic Appointments

Honors & Awards

  • Stephen Q. Shafer Award for Humanism in Neurology, Columbia University Neurology Residents (2014)

Professional Education

  • Fellowship:University of Utah School of Medicine Registrar (2006) UT
  • Board Certification: Neurology, American Board of Psychiatry and Neurology (2005)
  • Residency:University of Utah School of Medicine (2004) UT
  • Internship:University of Utah School of Medicine (2001) UT
  • Medical Education:University of Alabama at Birmingham (2000) AL
  • Fellowship, University of Utah School of Medicine, Neurogenetics (2006)
  • Residency, University of Utah School of Medicine, Neurology (2004)
  • Internship, University of Utah School of Medicine, Internal Medicine (2001)
  • PhD, University of Alabama, Biochemistry (1999)
  • MD, University of Alabama School of Medicine, Medical Degree (2000)


All Publications

  • Loss-of-Function Mutations in LGI4, a Secreted Ligand Involved in Schwann Cell Myelination, Are Responsible for Arthrogryposis Multiplex Congenita AMERICAN JOURNAL OF HUMAN GENETICS Xue, S., Maluenda, J., Marguet, F., Shboul, M., Quevarec, L., Bonnard, C., Ng, A. Y., Tohari, S., Thong Teck Tan, T. T., Kong, M. K., Monaghan, K. G., Cho, M. T., Siskind, C. E., Sampson, J. B., Rocha, C. T., Alkazaleh, F., Gonzales, M., Rigonnot, L., Whalen, S., Gut, M., Gut, I., Bucourt, M., Venkatesh, B., Laquerriere, A., Reversade, B., Melki, J. 2017; 100 (4): 659-665


    Arthrogryposis multiplex congenita (AMC) is a developmental condition characterized by multiple joint contractures resulting from reduced or absent fetal movements. Through genetic mapping of disease loci and whole-exome sequencing in four unrelated multiplex families presenting with severe AMC, we identified biallelic loss-of-function mutations in LGI4 (leucine-rich glioma-inactivated 4). LGI4 is a ligand secreted by Schwann cells that regulates peripheral nerve myelination via its cognate receptor ADAM22 expressed by neurons. Immunolabeling experiments and transmission electron microscopy of the sciatic nerve from one of the affected individuals revealed a lack of myelin. Functional tests using affected individual-derived iPSCs showed that these germline mutations caused aberrant splicing of the endogenous LGI4 transcript and in a cell-based assay impaired the secretion of truncated LGI4 protein. This is consistent with previous studies reporting arthrogryposis in Lgi4-deficient mice due to peripheral hypomyelination. This study adds to the recent reports implicating defective axoglial function as a key cause of AMC.

    View details for DOI 10.1016/j.ajhg.2017.02.006

    View details for Web of Science ID 000398389600008

    View details for PubMedID 28318499

  • Specific functional pathologies of Cx43 mutations associated with oculodentodigital dysplasia. Molecular biology of the cell Kelly, J. J., Esseltine, J. L., Shao, Q., Jabs, E. W., Sampson, J., Auranen, M., Bai, D., Laird, D. W. 2016; 27 (14): 2172-2185


    Oculodentodigital dysplasia (ODDD) is a rare genetic disease that affects the development of multiple organs in the human body. More than 70 mutations in the gap junction connexin43 (Cx43) gene, GJA1, are associated with ODDD, most of which are inherited in an autosomal dominant manner. Many patients exhibit similar clinical presentations. However, there is high intrafamilial and interfamilial phenotypic variability. To better understand this variability, we established primary human dermal fibroblast cultures from several ODDD patients and unaffected controls. In the present study, we characterized three fibroblast lines expressing heterozygous p.L7V, p.G138R, and p.G143S Cx43 variants. All ODDD fibroblasts exhibited slower growth, reduced migration, and defective cell polarization, traits common to all ODDD fibroblasts studied so far. However, we found striking differences in overall expression levels, with p.L7V down-regulated at the mRNA and protein level. Although all of the Cx43 variants could traffic to the cell surface, there were stark differences in gap junction plaque formation, gap junctional intercellular communication, Cx43 phosphorylation, and hemichannel activity among Cx43 variants, as well as subtle differences in myofibroblast differentiation. Together these findings enabled us to discover mutation-specific pathologies that may help to predict future clinical outcomes.

    View details for DOI 10.1091/mbc.E16-01-0062

    View details for PubMedID 27226478

  • Manipulating Cx43 expression triggers gene reprogramming events in dermal fibroblasts from oculodentodigital dysplasia patients. Biochemical journal Esseltine, J. L., Shao, Q., Huang, T., Kelly, J. J., Sampson, J., Laird, D. W. 2015; 472 (1): 55-69


    Oculodentodigital dysplasia (ODDD) is primarily an autosomal dominant disorder linked to over 70 GJA1 gene [connexin43 (Cx43)] mutations. For nearly a decade, our laboratory has been investigating the relationship between Cx43 and ODDD by expressing disease-linked mutants in reference cells, tissue-relevant cell lines, 3D organ cultures and by using genetically modified mouse models of human disease. Although salient features of Cx43 mutants have been revealed, these models do not necessarily reflect the complexity of the human context. To further overcome these limitations, we have acquired dermal fibroblasts from two ODDD-affected individuals harbouring D3N and V216L mutations in Cx43, along with familial controls. Using these ODDD patient dermal fibroblasts, which naturally produce less GJA1 gene product, along with RNAi and RNA activation (RNAa) approaches, we show that manipulating Cx43 expression triggers cellular gene reprogramming. Quantitative RT-PCR, Western blot and immunofluorescent analysis of ODDD patient fibroblasts show unusually high levels of extracellular matrix (ECM)-interacting proteins, including integrin α5β1, matrix metalloproteinases as well as secreted ECM proteins collagen-I and laminin. Cx43 knockdown in familial control cells produces similar effects on ECM expression, whereas Cx43 transcriptional up-regulation using RNAa decreases production of collagen-I. Interestingly, the enhanced levels of ECM-associated proteins in ODDD V216L fibroblasts is not only a consequence of increased ECM gene expression, but also due to an apparent deficit in collagen-I secretion which may further contribute to impaired collagen gel contraction in ODDD fibroblasts. These findings further illuminate the altered function of Cx43 in ODDD-affected individuals and highlight the impact of manipulating Cx43 expression in human cells.

    View details for DOI 10.1042/BJ20150652

    View details for PubMedID 26349540

  • Nuclear localization of SMN and FUS is not altered in fibroblasts from patients with sporadic ALS AMYOTROPHIC LATERAL SCLEROSIS AND FRONTOTEMPORAL DEGENERATION Kariya, S., Sampson, J. B., Northrop, L. E., Lucarelli, C. M., Naini, A. B., Re, D. B., Hirano, M., Mitsumoto, H. 2014; 15 (7-8): 581-587


    Abstract Sporadic amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with no established biological marker. Recent observation of a reduced number of gems (survival motor neuron protein (SMN)-positive nuclear bodies) in cells from patients with familial ALS and the mouse models suggests an involvement of SMN in ALS pathology. At a molecular level, fused in sarcoma (FUS), one of the familial ALS-linked proteins, has been demonstrated to directly interact with SMN, while impaired nuclear localization of mutated FUS causes defective gem formation. Our objective was to determine whether gems and/or nuclear FUS levels in skin derived fibroblasts from sporadic ALS patients are consistently reduced and thus could constitute a novel and readily available biomarker of the disease. Fibroblasts from 20 patients and 17 age-matched healthy controls were cultured and co-immunostained for SMN and FUS. Results showed that no difference was detected between the two groups in the number of gems and in expression pattern of FUS. The number of gems negatively correlated with the age at biopsy in both ALS and control subjects. In conclusion, the expression pattern of SMN and FUS in fibroblasts cannot serve as a biomarker for sporadic ALS. Donor age-dependent gem reduction is a novel observation that links SMN with cellular senescence.

    View details for DOI 10.3109/21678421.2014.907319

    View details for Web of Science ID 000346926100017

    View details for PubMedID 24809826

  • ATALUREN TREATMENT OF PATIENTS WITH NONSENSE MUTATION DYSTROPHINOPATHY MUSCLE & NERVE Bushby, K., Finkel, R., Wong, B., Barohn, R., Campbell, C., Comi, G. P., Connolly, A. M., Day, J. W., Flanigan, K. M., Goemans, N., Jones, K. J., Mercuri, E., Quinlivan, R., Renfroe, J. B., Russman, B., Ryan, M. M., Tulinius, M., Voit, T., Moore, S. A., Sweeney, H. L., Abresch, R. T., Coleman, K. L., Eagle, M., Florence, J., Gappmaier, E., Glanzman, A. M., Henricson, E., Barth, J., Elfring, G. L., Reha, A., Spiegel, R. J., O'Donnell, M. W., Peltz, S. W., McDonald, C. M. 2014; 50 (4): 477-487


    Dystrophinopathy is a rare, severe muscle disorder, and nonsense mutations are found in 13% of cases. Ataluren was developed to enable ribosomal readthrough of premature stop codons in nonsense mutation (nm) genetic disorders.Randomized, double-blind, placebo-controlled study; males ≥5 years with nm-dystrophinopathy received study drug orally 3 times daily, ataluren 10, 10, 20 mg/kg (N = 57); ataluren 20, 20, 40 mg/kg (N = 60); or placebo (N = 57) for 48 weeks. The primary endpoint was change in 6-Minute Walk Distance (6MWD) at Week 48.Ataluren was generally well tolerated. The primary endpoint favored ataluren 10, 10, 20 mg/kg versus placebo; the week 48 6MWD Δ = 31.3 meters, post hoc P = 0.056. Secondary endpoints (timed function tests) showed meaningful differences between ataluren 10, 10, 20 mg/kg, and placebo.As the first investigational new drug targeting the underlying cause of nm-dystrophinopathy, ataluren offers promise as a treatment for this orphan genetic disorder with high unmet medical need. Muscle Nerve 50: 477-487, 2014.

    View details for DOI 10.1002/mus.24332

    View details for Web of Science ID 000342634100002

    View details for PubMedID 25042182

  • The G60S Cx43 mutant enhances keratinocyte proliferation and differentiation EXPERIMENTAL DERMATOLOGY Churko, J. M., Kelly, J. J., Macdonald, A., Lee, J., Sampson, J., Bai, D., Laird, D. W. 2012; 21 (8): 612-618


    Transient knock-down of the gap junction protein Cx43 by antisense and siRNA, or gap junction block with mimetic peptides, have been shown to enhance epidermal wound healing. However, patients with oculodentodigital dysplasia (ODDD) express mutant Cx43 that leads to a chronic reduction in gap junctional intercellular communication. To determine whether mutant Cx43 in keratinocytes would impact upon the wound healing process, we localized Cx43 in human and mouse skin tissue expressing mutant Cx43 and assessed the ability of primary keratinocytes derived from a mouse model of ODDD to proliferate, migrate and differentiate. In the epidermis from an ODDD patient and in the epidermis of mice expressing the G60S mutant or in keratinocytes obtained from mutant mice, Cx43 was frequently found within intracellular compartments and rarely localized to punctate sites of cell-cell apposition. Primary keratinocytes derived from G60S mutant mice proliferated faster but migrated similarly to keratinocytes derived from wild-type control mice. Keratinocytes derived from mutant mice expressed abundant Cx43 and higher levels of involucrin and loricrin under low calcium conditions. However, after calcium-induced differentiation, similar levels of Cx43, involucrin and loricrin were observed. Thus, we conclude that during wound healing, mutant Cx43 may enhance keratinocyte proliferation and promote early differentiation of keratinocytes.

    View details for DOI 10.1111/j.1600-0625.2012.01532.x

    View details for Web of Science ID 000306222700009

    View details for PubMedID 22775996

  • Human Dermal Fibroblasts Derived from Oculodentodigital Dysplasia Patients Suggest That Patients May Have Wound-Healing Defects HUMAN MUTATION Churko, J. M., Shao, Q., Gong, X., Swoboda, K. J., Bai, D., Sampson, J., Laird, D. W. 2011; 32 (4): 456-466


    Oculodentodigital dysplasia (ODDD) is primarily an autosomal dominant human disease caused by any one of over 60 mutations in the GJA1 gene encoding the gap junction protein Cx43. In the present study, wound healing was investigated in a G60S ODDD mutant mouse model and by using dermal fibroblasts isolated from two ODDD patients harboring the p.D3N and p.V216L mutants along with dermal fibroblasts isolated from their respective unaffected relatives. Punch biopsies revealed a delay in wound closure in the G60S mutant mice in comparison to wild-type littermates, and this delay appeared to be due to defects in the dermal fibroblasts. Although both the p.D3N and p.V216L mutants reduced gap junctional intercellular communication in human dermal fibroblasts, immunolocalization studies revealed that Cx43 gap junctions were prevalent at the cell surface of p.D3N expressing fibroblasts but greatly reduced in p.V216L expressing fibroblasts. Mutant expressing fibroblasts were further found to have reduced proliferation and migration capabilities. Finally, in response to TGFβ1, mutant expressing fibroblasts expressed significantly less alpha smooth muscle actin suggesting they were inefficient in their ability to differentiate into myofibroblasts. Collectively, our results suggest that ODDD patients may have subclinical defects in wound healing due to impaired function of dermal fibroblasts.

    View details for DOI 10.1002/humu.21472

    View details for Web of Science ID 000288464100018

    View details for PubMedID 21305658

  • Nonsense Mutation-Associated Becker Muscular Dystrophy: Interplay Between Exon Definition and Splicing Regulatory Elements within the DMD Gene HUMAN MUTATION Flanigan, K. M., Dunn, D. M., von Niederhausern, A., Soltanzadeh, P., Howard, M. T., Sampson, J. B., Swoboda, K. J., Bromberg, M. B., Mendell, J. R., Taylor, L. E., Anderson, C. B., Pestronk, A., Florence, J. M., Connolly, A. M., Mathews, K. D., Wong, B., Finkel, R. S., Bonnemann, C. G., Day, J. W., McDonald, C., Weiss, R. B. 2011; 32 (3): 299-308


    Nonsense mutations are usually predicted to function as null alleles due to premature termination of protein translation. However, nonsense mutations in the DMD gene, encoding the dystrophin protein, have been associated with both the severe Duchenne Muscular Dystrophy (DMD) and milder Becker Muscular Dystrophy (BMD) phenotypes. In a large survey, we identified 243 unique nonsense mutations in the DMD gene, and for 210 of these we could establish definitive phenotypes. We analyzed the reading frame predicted by exons flanking those in which nonsense mutations were found, and present evidence that nonsense mutations resulting in BMD likely do so by inducing exon skipping, confirming that exonic point mutations affecting exon definition have played a significant role in determining phenotype. We present a new model based on the combination of exon definition and intronic splicing regulatory elements for the selective association of BMD nonsense mutations with a subset of DMD exons prone to mutation-induced exon skipping.

    View details for DOI 10.1002/humu.21426

    View details for Web of Science ID 000288034100007

    View details for PubMedID 21972111

  • Clinical and genetic characterization of manifesting carriers of DMD mutations NEUROMUSCULAR DISORDERS Soltanzadeh, P., Friez, M. J., Dunn, D., von Niederhausern, A., Gurvich, O. L., Swoboda, K. J., Sampson, J. B., Pestronk, A., Connolly, A. M., Florence, J. M., Finkel, R. S., Boennemann, C. G., Medne, L., Mendell, J. R., Mathews, K. D., Wong, B. L., Sussman, M. D., Zonana, J., Kovak, K., Gospe, S. M., Gappmaier, E., Taylor, L. E., Howard, M. T., Weiss, R. B., Flanigan, K. M. 2010; 20 (8): 499-504


    Manifesting carriers of DMD gene mutations may present diagnostic challenges, particularly in the absence of a family history of dystrophinopathy. We review the clinical and genetic features in 15 manifesting carriers identified among 860 subjects within the United Dystrophinopathy Project, a large clinical dystrophinopathy cohort whose members undergo comprehensive DMD mutation analysis. We defined manifesting carriers as females with significant weakness, excluding those with only myalgias/cramps. DNA extracted from peripheral blood was used to study X-chromosome inactivation patterns. Among these manifesting carriers, age at symptom onset ranged from 2 to 47 years. Seven had no family history and eight had male relatives with Duchenne muscular dystrophy (DMD). Clinical severity among the manifesting carriers varied from a DMD-like progression to a very mild Becker muscular dystrophy-like phenotype. Eight had exonic deletions or duplications and six had point mutations. One patient had two mutations (an exonic deletion and a splice site mutation), consistent with a heterozygous compound state. The X-chromosome inactivation pattern was skewed toward non-random in four out of seven informative deletions or duplications but was random in all cases with nonsense mutations. We present the results of DMD mutation analysis in this manifesting carrier cohort, including the first example of a presumably compound heterozygous DMD mutation. Our results demonstrate that improved molecular diagnostic methods facilitate the identification of DMD mutations in manifesting carriers, and confirm the heterogeneity of mutational mechanisms as well as the wide spectrum of phenotypes.

    View details for DOI 10.1016/j.nmd.2010.05.010

    View details for Web of Science ID 000281347900003

    View details for PubMedID 20630757

  • Identification of Uncommon Recurrent Potocki-Lupski Syndrome-Associated Duplications and the Distribution of Rearrangement Types and Mechanisms in PTLS AMERICAN JOURNAL OF HUMAN GENETICS Zhang, F., Potocki, L., Sampson, J. B., Liu, P., Sanchez-Valle, A., Robbins-Furman, P., Delicado Navarro, A., Wheeler, P. G., Spence, J. E., Brasington, C. K., Withers, M. A., Lupski, J. R. 2010; 86 (3): 462-470


    Nonallelic homologous recombination (NAHR) can mediate recurrent rearrangements in the human genome and cause genomic disorders. Smith-Magenis syndrome (SMS) and Potocki-Lupski syndrome (PTLS) are genomic disorders associated with a 3.7 Mb deletion and its reciprocal duplication in 17p11.2, respectively. In addition to these common recurrent rearrangements, an uncommon recurrent 5 Mb SMS-associated deletion has been identified. However, its reciprocal duplication predicted by the NAHR mechanism had not been identified. Here we report the molecular assays on 74 subjects with PTLS-associated duplications, 35 of whom are newly investigated. By both oligonucleotide-based comparative genomic hybridization and recombination hot spot analyses, we identified two cases of the predicted 5 Mb uncommon recurrent PTLS-associated duplication. Interestingly, the crossovers occur in proximity to a recently delineated allelic homologous recombination (AHR) hot spot-associated sequence motif, further documenting the common hot spot features shared between NAHR and AHR. An additional eight subjects with nonrecurrent PTLS duplications were identified. The smallest region of overlap (SRO) for all of the 74 PTLS duplications examined is narrowed to a 125 kb interval containing only RAI1, a gene recently further implicated in autism. Sequence complexities consistent with DNA replication-based mechanisms were identified in four of eight (50%) newly identified nonrecurrent PTLS duplications. Our findings of the uncommon recurrent PTLS-associated duplication at a relative prevalence reflecting the de novo mutation rate and the distribution of 17p11.2 duplication types in PTLS reveal insights into both the contributions of new mutations and the different underlying mechanisms that generate genomic rearrangements causing genomic disorders.

    View details for DOI 10.1016/j.ajhg.2010.02.001

    View details for Web of Science ID 000275678800018

    View details for PubMedID 20188345

  • Mutational Spectrum of DMD Mutations in Dystrophinopathy Patients: Application of Modern Diagnostic Techniques to a Large Cohort HUMAN MUTATION Flanigan, K. M., Dunn, D. M., von Niederhausern, A., Soltanzadeh, P., Gappmaier, E., Howard, M. T., Sampson, J. B., Mendell, J. R., Wall, C., King, W. M., Pestronk, A., Florence, J. M., Connolly, A. M., Mathews, K. D., Stephan, C. M., Laubenthal, K. S., Wong, B. L., Morehart, P. J., Meyer, A., Finkel, R. S., Bonnemann, C. G., Medne, L., Day, J. W., Dalton, J. C., Margolis, M. K., Hinton, V. J., Weiss, R. B. 2009; 30 (12): 1657-1666


    Mutations in the DMD gene, encoding the dystrophin protein, are responsible for the dystrophinopathies Duchenne Muscular Dystrophy (DMD), Becker Muscular Dystrophy (BMD), and X-linked Dilated Cardiomyopathy (XLDC). Mutation analysis has traditionally been challenging, due to the large gene size (79 exons over 2.2 Mb of genomic DNA). We report a very large aggregate data set comprised of DMD mutations detected in samples from patients enrolled in the United Dystrophinopathy Project, a multicenter research consortium, and in referral samples submitted for mutation analysis with a diagnosis of dystrophinopathy. We report 1,111 mutations in the DMD gene, including 891 mutations with associated phenotypes. These results encompass 506 point mutations (including 294 nonsense mutations) and significantly expand the number of mutations associated with the dystrophinopathies, highlighting the utility of modern diagnostic techniques. Our data supports the uniform hypermutability of CGA>TGA mutations, establishes the frequency of polymorphic muscle (Dp427m) protein isoforms and reveals unique genomic haplotypes associated with "private" mutations. We note that 60% of these patients would be predicted to benefit from skipping of a single DMD exon using antisense oligonucleotide therapy, and 62% would be predicted to benefit from an inclusive multiexonskipping approach directed toward exons 45 through 55.

    View details for DOI 10.1002/humu.21114

    View details for Web of Science ID 000272796400007

    View details for PubMedID 19937601

  • Paraneoplastic myopathy: response to intravenous immunoglobulin NEUROMUSCULAR DISORDERS Sampson, J. B., Smith, S. M., Smith, A. G., Singleton, J. R., Chin, S., Pestronk, A., Flanigan, K. M. 2007; 17 (5): 404-408


    Necrotizing myopathy is an unusual and severe form of paraneoplastic myopathy in which inflammation is minimal or absent. We report two cases of necrotizing myopathy which demonstrated significant response to intravenous immunoglobulin (IVIG) (one in spite of tumor progression). A third case represents the first association of anti-signal recognition particle (anti-SRP) syndrome with large-cell lung cancer. These cases highlight the role of histopathologic diagnosis in directing the treatment of paraneoplastic myopathy, and the role for IVIG in treatment of the syndrome.

    View details for DOI 10.1016/j.nmd.2007.01.004

    View details for Web of Science ID 000247041000007

    View details for PubMedID 17336069

  • Inhibition of human surfactant protein a function by oxidation intermediates of nitrite FREE RADICAL BIOLOGY AND MEDICINE Davis, I. C., Zhu, S., Sampson, J. B., Crow, J. P., Matalon, S. 2002; 33 (12): 1703-1713


    NitraNitration of protein tyrosine residues by peroxynitrite (ONOO - ) has been implicated in a variety of inflammatory diseases such as acute respiratory distress syndrome (ARDS). Pulmonary surfactant protein A (SP-A) has multiple functions including host defense. We report here that a mixture of hypochlorous acid (HOCl) and nitrite (NO 2 - ) induces nitration, oxidation, and chlorination of tyrosine residues in human SP-A and inhibits SP-A's ability to aggregate lipids and bind mannose. Nitration and oxidation of SP-A was not altered by the presence of lipids, suggesting that proteins are preferred targets in lipid-rich mixtures such as pulmonary surfactant. Moreover, both horseradish peroxidase and myeloperoxidase (MPO) can utilize NO 2 - and hydrogen peroxide (H 2 O 2 ) as substrates to catalyze tyrosine nitration in SP-A and inhibit its lipid aggregation function. SP-A nitration and oxidation by MPO is markedly enhanced in the presence of physiological concentrations of Cl - and the lipid aggregation function of SP-A is completely abolished. Collectively, our results suggest that MPO released by activated neutrophils during inflammation utilizes physiological or pathological levels of NO 2 - to nitrate proteins, and may provide an additional mechanism in addition to ONOO - formation, for tissue injury in ARDS and other inflammatory diseases associated with upregulated *NO and oxidant production.

    View details for Web of Science ID 000179840700010

    View details for PubMedID 12488138

  • Abstract

    Inhibition of nitric oxide synthesis prevents rat embryonic motor neurons from undergoing apoptosis when initially cultured without brain-derived neurotrophic factor. Using an improved cell culture medium, we found that the partial withdrawal of trophic support even weeks after motor neurons had differentiated into a mature phenotype still induced apoptosis through a process dependent upon nitric oxide. However, nitric oxide itself was not directly toxic to motor neurons. To investigate whether intracellular superoxide contributed to nitric oxide-dependent apoptosis, we developed a novel method using pH-sensitive liposomes to deliver Cu, Zn superoxide dismutase intracellularly into motor neurons. Intracellular superoxide dismutase prevented motor neuron apoptosis from trophic factor withdrawal, whereas empty liposomes, inactivated superoxide dismutase in liposomes or extracellular superoxide dismutase did not. Neither hydrogen peroxide nor nitrite added separately or in combination affected motor neuron survival. Our results suggest that a partial reduction in trophic support induced motor neuron apoptosis by a process requiring the endogenous production of both nitric oxide and superoxide, irrespective of the extent of motor neuron maturation in culture.

    View details for Web of Science ID 000085619000016

    View details for PubMedID 10699756

  • Myeloperoxidase and horseradish peroxidase catalyze tyrosine nitration in proteins from nitrite and hydrogen peroxide ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS Sampson, J. B., Ye, Y. Z., Rosen, H., Beckman, J. S. 1998; 356 (2): 207-213


    Nitration of tyrosine residues in proteins occurs in a wide range of inflammatory diseases involving neutrophil and macrophage activation. We report that both myeloperoxidase (MPO) and horseradish peroxidase (HRP) utilize nitrite (NO2-) and hydrogen peroxide (H2O2) as substrates to catalyze tyrosine nitration in proteins. MPO was approximately 10 times more effective than HRP as a nitration catalyst of bovine serum albumin (BSA). Nitration of BSA by MPO did not require chloride as a cofactor. Physiologic levels of chloride did not significantly inhibit nitration by MPO. Oxidation of chloride to hypochlorous acid (HOCl) is catalyzed by MPO but not by HRP, yet HRP also catalyzed nitration from hydrogen peroxide plus nitrite. Therefore, HOCl formation was not obligatory for tyrosine nitration. Although HOCl plus nitrite can nitrate the amino acid tyrosine in simple solutions, protein nitration by HOCl plus nitrite was not observed in heart homogenates, probably due to the presence of multiple alternative targets of both HOCl and HOCl plus nitrite. In contrast, MPO catalyzed nitration of many proteins in rat heart homogenates using NO2- plus H2O2, suggesting that peroxidase-catalyzed nitration of tyrosine could occur in the presence of competing substrates in vivo. HOCl could substitute for H2O2 as the oxidizing substrate for nitration of either BSA or tissue homogenates catalyzed by either peroxidase. Activated neutrophils may generate nitrotyrosine by several mechanisms, including peroxynitrite, HOCl plus nitrite, and a chloride-independent mechanism involving MPO, nitrite, and hydrogen peroxide.

    View details for Web of Science ID 000075362000013

    View details for PubMedID 9705211

  • DIFFERENTIAL MODULATION OF ASTROCYTE CYTOKINE GENE-EXPRESSION BY TGF-BETA JOURNAL OF IMMUNOLOGY Benveniste, E. N., Kwon, J. B., Chung, W. J., Sampson, J., Pandya, K., Tang, L. P. 1994; 153 (11): 5210-5221


    In this study, we demonstrate that TGF-beta inhibits TNF-alpha expression, and induces/enhances IL-6 expression by primary rat astrocytes. Treatment of astrocytes with TGF-beta alone had no effect on TNF-alpha mRNA or protein expression; however, TGF-beta suppressed induction of TNF-alpha expression by three different stimuli (IFN-gamma/LPS, IFN-gamma/IL-1 beta, TNF-alpha) at both the protein and mRNA level. The extent of TGF-beta-mediated inhibition was greatest when astrocytes were pretreated with TGF-beta for 6 to 24 h, then exposed to the inducing stimuli. Inhibition of TNF-alpha mRNA steady-state levels by TGF-beta was a result of inhibition of TNF-alpha gene transcription, rather than degradation of the TNF-alpha message. In contrast, TGF-beta alone induced expression of IL-6 by astrocytes and synergized with two other cytokines, IL-1 beta and TNF-alpha, for enhanced IL-6 expression. TGF-beta-induced/enhanced IL-6 expression was mediated by transcriptional activation of the IL-6 gene. These results indicate that TGF-beta is an important regulator of cytokine production by astrocytes under inflammatory conditions in the brain.

    View details for Web of Science ID A1994PT30100039

    View details for PubMedID 7963576