Bio

Academic Appointments


Administrative Appointments


  • Director, Stanford MSTP (2008 - 2013)
  • Associate Director, Stanford Medical Scientist Training Program (2001 - 2008)
  • Member, Medical Science Review Board, Juvenile Diabetes Research Foundation (2002 - Present)

Honors & Awards


  • Ho-Am Prize in Medicine, Ho-Am Foundation (2014)
  • Gerald and Kayla Grodsky Basic Science Research Award, Juvenile Diabetes Research Foundation (JDRF) (2013)
  • Investigator, Howard Hughes Medical Institute (2008-present)
  • Pew Biomedical Research Scholar, The Pew Charitable Trusts (1999-2003)
  • Named Investigator Award, Stanford-NIH Digestive Diseases Center (2000)
  • Career Development Award, American Diabetes Association (1999-2003)
  • Faculty Scholar Award, Donald E. and Delia B. Baxter Foundation (1999-2001)
  • Henry J. Kaiser Family Foundation Award for Excellence in Preclinical Teaching, Stanford University School of Medicine (2002)
  • Junior Faculty Scholar, Howard Hughes Medical Institute/Stanford University School of Medicine (1999-2001)
  • Faculty Scholar Award, SmithKline Beecham-Stanford University School of Medicine (1999-2001)
  • Living and Giving Award, Juvenile Diabetes Research Foundation Northern California Chapter (2004)

Professional Education


  • A.B., Harvard University, Biochemical Sciences (1985)
  • M.D., Stanford University, Medicine (1992)
  • Ph.D., Stanford University, Biochemistry (1992)

Research & Scholarship

Current Research and Scholarly Interests


Organ development requires mechanisms to establish an integrated, stereotyped tissue pattern from multiple distinct cellular components. Many vital organs derive from the endodermal and mesodermal germ layers to form the gastrointestinal and respiratory tracts, yet little is known about the genetic programs that coordinate steps culminating in proper organ morphogenesis and axial position, cell differentiation and physiologic function. Our goal is to identify and understand the pathways that govern organogenesis of the pancreas, a vital organ with endocrine and exocrine functions.


We are using Drosophila, chicks and mice, organisms accessible to embryological, genetic and molecular methods, to identify cell interactions and signaling pathways that regulate early steps in pancreatic islet development. Some of the pathways active during ontogeny also regulate pancreatic growth during adulthood, and we are studying the role of these genetic pathways in growth control and function of the mature pancreas in mice. Armed with an understanding of the mechanisms regulating normal development of insulin-producing cells and other islet cells, we have been able to differentiate functional glucose-responsive islets from embryonic stem cells and other cell lines. These are capable of rescuing glucose regulation and survival in experimental animal models of diabetes mellitus. We are now using this in vitro culture system to isolate candidate islet stem/precursor populations from adult human stem cell populations. We are also using Drosophila to study neuroendocrine cells that govern metabolism. We have discovered that two cell types, one which produces insulin, the other which produces a glucagon-like peptide called AKH, are crucial regulators of glucose homeostasis in Drosophila. Genetic, biochemical, and electrophysiologic studies are being used to elucidate the programs that control development and function of these cells, which comprise the Drosophila endocrine 'pancreas'. In turn, we expect that these studies will identify important conserved functions that govern islet cell biology.

Teaching

2013-14 Courses


Graduate and Fellowship Programs


Publications

Journal Articles


  • Reconstituting pancreas development from purified progenitor cells reveals genes essential for islet differentiation PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Sugiyama, T., Benitez, C. M., Ghodasara, A., Liu, L., McLean, G. W., Lee, J., Blauwkamp, T. A., Nusse, R., Wright, C. V., Gu, G., Kim, S. K. 2013; 110 (31): 12691-12696

    Abstract

    Developmental biology is challenged to reveal the function of numerous candidate genes implicated by recent genome-scale studies as regulators of organ development and diseases. Recapitulating organogenesis from purified progenitor cells that can be genetically manipulated would provide powerful opportunities to dissect such gene functions. Here we describe systems for reconstructing pancreas development, including islet ?-cell and ?-cell differentiation, from single fetal progenitor cells. A strict requirement for native genetic regulators of in vivo pancreas development, such as Ngn3, Arx, and Pax4, revealed the authenticity of differentiation programs in vitro. Efficient genetic screens permitted by this system revealed that Prdm16 is required for pancreatic islet development in vivo. Discovering the function of genes regulating pancreas development with our system should enrich strategies for regenerating islets for treating diabetes mellitus.

    View details for DOI 10.1073/pnas.1304507110

    View details for Web of Science ID 000322441500050

    View details for PubMedID 23852729

  • Neonatal beta Cell Development in Mice and Humans Is Regulated by Calcineurin/NFAT DEVELOPMENTAL CELL Goodyer, W. R., Gu, X., Liu, Y., Bottino, R., Crabtree, G. R., Kim, S. K. 2012; 23 (1): 21-34

    Abstract

    Little is known about the mechanisms governing neonatal growth and maturation of organs. Here we demonstrate that calcineurin/Nuclear Factor of Activated T cells (Cn/NFAT) signaling regulates neonatal pancreatic development in mouse and human islets. Inactivation of calcineurin b1 (Cnb1) in mouse islets impaired dense core granule biogenesis, decreased insulin secretion, and reduced cell proliferation and mass, culminating in lethal diabetes. Pancreatic ? cells lacking Cnb1 failed to express genes revealed to be direct NFAT targets required for replication, insulin storage, and secretion. In contrast, glucokinase activation stimulated Cn-dependent expression of these genes. Calcineurin inhibitors, such as tacrolimus, used for human immunosuppression, induce diabetes. Tacrolimus exposure reduced Cn/NFAT-dependent expression of factors essential for insulin dense core granule formation and secretion and neonatal ? cell proliferation, consistent with our genetic studies. Discovery of conserved pathways regulating ? cell maturation and proliferation suggests new strategies for controlling ? cell growth or replacement in human islet diseases.

    View details for DOI 10.1016/j.devcel.2012.05.014

    View details for Web of Science ID 000306583800007

    View details for PubMedID 22814600

  • PDGF signalling controls age-dependent proliferation in pancreatic beta-cells NATURE Chen, H., Gu, X., Liu, Y., Wang, J., Wirt, S. E., Bottino, R., Schorle, H., Sage, J., Kim, S. K. 2011; 478 (7369): 349-?

    Abstract

    Determining the signalling pathways that direct tissue expansion is a principal goal of regenerative biology. Vigorous pancreatic ?-cell replication in juvenile mice and humans declines with age, and elucidating the basis for this decay may reveal strategies for inducing ?-cell expansion, a long-sought goal for diabetes therapy. Here we show that platelet-derived growth factor receptor (Pdgfr) signalling controls age-dependent ?-cell proliferation in mouse and human pancreatic islets. With age, declining ?-cell Pdgfr levels were accompanied by reductions in ?-cell enhancer of zeste homologue 2 (Ezh2) levels and ?-cell replication. Conditional inactivation of the Pdgfra gene in ?-cells accelerated these changes, preventing mouse neonatal ?-cell expansion and adult ?-cell regeneration. Targeted human PDGFR-? activation in mouse ?-cells stimulated Erk1/2 phosphorylation, leading to Ezh2-dependent expansion of adult ?-cells. Adult human islets lack PDGF signalling competence, but exposure of juvenile human islets to PDGF-AA stimulated ?-cell proliferation. The discovery of a conserved pathway controlling age-dependent ?-cell proliferation indicates new strategies for ?-cell expansion.

    View details for DOI 10.1038/nature10502

    View details for Web of Science ID 000296021100038

    View details for PubMedID 21993628

  • Calcineurin/NFAT signalling regulates pancreatic beta-cell growth and function NATURE Heit, J. J., Apelqvist, A. A., Gu, X., Winslow, M. M., Neilson, J. R., Crabtree, G. R., Kim, S. K. 2006; 443 (7109): 345-349

    Abstract

    The growth and function of organs such as pancreatic islets adapt to meet physiological challenges and maintain metabolic balance, but the mechanisms controlling these facultative responses are unclear. Diabetes in patients treated with calcineurin inhibitors such as cyclosporin A indicates that calcineurin/nuclear factor of activated T-cells (NFAT) signalling might control adaptive islet responses, but the roles of this pathway in beta-cells in vivo are not understood. Here we show that mice with a beta-cell-specific deletion of the calcineurin phosphatase regulatory subunit, calcineurin b1 (Cnb1), develop age-dependent diabetes characterized by decreased beta-cell proliferation and mass, reduced pancreatic insulin content and hypoinsulinaemia. Moreover, beta-cells lacking Cnb1 have a reduced expression of established regulators of beta-cell proliferation. Conditional expression of active NFATc1 in Cnb1-deficient beta-cells rescues these defects and prevents diabetes. In normal adult beta-cells, conditional NFAT activation promotes the expression of cell-cycle regulators and increases beta-cell proliferation and mass, resulting in hyperinsulinaemia. Conditional NFAT activation also induces the expression of genes critical for beta-cell endocrine function, including all six genes mutated in hereditary forms of monogenic type 2 diabetes. Thus, calcineurin/NFAT signalling regulates multiple factors that control growth and hallmark beta-cell functions, revealing unique models for the pathogenesis and therapy of diabetes.

    View details for DOI 10.1038/nature05097

    View details for Web of Science ID 000240622000048

    View details for PubMedID 16988714

  • Conserved mechanisms of glucose sensing and regulation by Drosophila corpora cardiaca cells NATURE Kim, S. K., Rulifson, E. J. 2004; 431 (7006): 316-320

    Abstract

    Antagonistic activities of glucagon and insulin control metabolism in mammals, and disruption of this balance underlies diabetes pathogenesis. Insulin-producing cells (IPCs) in the brain of insects such as Drosophila also regulate serum glucose, but it remains unclear whether insulin is the sole hormonal regulator of glucose homeostasis and whether mechanisms of glucose-sensing and response in IPCs resemble those in pancreatic islets. Here we show, by targeted cell ablation, that Drosophila corpora cardiaca (CC) cells of the ring gland are also essential for larval glucose homeostasis. Unlike IPCs, CC cells express Drosophila cognates of sulphonylurea receptor (Sur) and potassium channel (Ir), proteins that comprise ATP-sensitive potassium channels regulating hormone secretion by islets and other mammalian glucose-sensing cells. They also produce adipokinetic hormone, a polypeptide with glucagon-like functions. Glucose regulation by CC cells is impaired by exposure to sulphonylureas, drugs that target the Sur subunit. Furthermore, ubiquitous expression of an akh transgene reverses the effect of CC ablation on serum glucose. Thus, Drosophila CC cells are crucial regulators of glucose homeostasis and they use glucose-sensing and response mechanisms similar to islet cells.

    View details for DOI 10.1038/nature02897

    View details for Web of Science ID 000223864000043

    View details for PubMedID 15372035

  • Topical hypochlorite ameliorates NF-kappa B-mediated skin diseases in mice JOURNAL OF CLINICAL INVESTIGATION Leung, T. H., Zhang, L. F., Wang, J., Ning, S., Knox, S. J., Kim, S. K. 2013; 123 (12): 5361-5370

    Abstract

    Nuclear factor-?B (NF-?B) regulates cellular responses to inflammation and aging, and alterations in NF-?B signaling underlie the pathogenesis of multiple human diseases. Effective clinical therapeutics targeting this pathway remain unavailable. In primary human keratinocytes, we found that hypochlorite (HOCl) reversibly inhibited the expression of CCL2 and SOD2, two NF-?B-dependent genes. In cultured cells, HOCl inhibited the activity of inhibitor of NF-?B kinase (IKK), a key regulator of NF-?B activation, by oxidizing cysteine residues Cys114 and Cys115. In NF-?B reporter mice, topical HOCl reduced LPS-induced NF-?B signaling in skin. We further evaluated topical HOCl use in two mouse models of NF-?B-driven epidermal disease. For mice with acute radiation dermatitis, topical HOCl inhibited the expression of NF-?B-dependent genes, decreased disease severity, and prevented skin ulceration. In aged mice, topical HOCl attenuated age-dependent production of p16INK4a and expression of the DNA repair gene Rad50. Additionally, skin of aged HOCl-treated mice acquired enhanced epidermal thickness and proliferation, comparable to skin in juvenile animals. These data suggest that topical HOCl reduces NF-?B-mediated epidermal pathology in radiation dermatitis and skin aging through IKK modulation and motivate the exploration of HOCl use for clinical aims.

    View details for DOI 10.1172/JCI70895

    View details for Web of Science ID 000327826100039

    View details for PubMedID 24231355

  • Expansion and conversion of human pancreatic ductal cells into insulin-secreting endocrine cells ELIFE Lee, J., Sugiyama, T., Liu, Y., Wang, J., Gu, X., Lei, J., Markmann, J. F., Miyazaki, S., Miyazaki, J., Szot, G. L., Bottino, R., Kim, S. K. 2013; 2

    Abstract

    Pancreatic islet ?-cell insufficiency underlies pathogenesis of diabetes mellitus; thus, functional ?-cell replacement from renewable sources is the focus of intensive worldwide effort. However, in vitro production of progeny that secrete insulin in response to physiological cues from primary human cells has proven elusive. Here we describe fractionation, expansion and conversion of primary adult human pancreatic ductal cells into progeny resembling native ?-cells. FACS-sorted adult human ductal cells clonally expanded as spheres in culture, while retaining ductal characteristics. Expression of the cardinal islet developmental regulators Neurog3, MafA, Pdx1 and Pax6 converted exocrine duct cells into endocrine progeny with hallmark ?-cell properties, including the ability to synthesize, process and store insulin, and secrete it in response to glucose or other depolarizing stimuli. These studies provide evidence that genetic reprogramming of expandable human pancreatic cells with defined factors may serve as a general strategy for islet replacement in diabetes. DOI: http://dx.doi.org/10.7554/eLife.00940.001.

    View details for DOI 10.7554/eLife.00940

    View details for Web of Science ID 000328641800001

    View details for PubMedID 24252877

  • Gene regulatory networks governing pancreas development. Developmental cell Arda, H. E., Benitez, C. M., Kim, S. K. 2013; 25 (1): 5-13

    Abstract

    Elucidation of cellular and gene regulatory networks (GRNs) governing organ development will accelerate progress toward tissue replacement. Here, we have compiled reference GRNs underlying pancreas development from data mining that integrates multiple approaches, including mutant analysis, lineage tracing, cell purification, gene expression and enhancer analysis, and biochemical studies of gene regulation. Using established computational tools, we integrated and represented these networks in frameworks that should enhance understanding of the surging output of genomic-scale genetic and epigenetic studies of pancreas development and diseases such as diabetes and pancreatic cancer. We envision similar approaches would be useful for understanding the development of other organs.

    View details for DOI 10.1016/j.devcel.2013.03.016

    View details for PubMedID 23597482

  • Combined modulation of polycomb and trithorax genes rejuvenates ? cell replication. The Journal of clinical investigation Zhou, J. X., Dhawan, S., Fu, H., Snyder, E., Bottino, R., Kundu, S., Kim, S. K., Bhushan, A. 2013; 123 (11): 4849-58

    Abstract

    Inadequate functional ? cell mass underlies both type 1 and type 2 diabetes. ? Cell growth and regeneration also decrease with age through mechanisms that are not fully understood. Age-dependent loss of enhancer of zeste homolog 2 (EZH2) prevents adult ? cell replication through derepression of the gene encoding cyclin-dependent kinase inhibitor 2a (INK4a). We investigated whether replenishing EZH2 could reverse the age-dependent increase of Ink4a transcription. We generated an inducible pancreatic ? cell-specific Ezh2 transgenic mouse model and showed that transgene expression of Ezh2 was sufficient to increase ? cell replication and regeneration in young adult mice. In mice older than 8 months, induction of Ezh2 was unable to repress Ink4a. Older mice had an enrichment of a trithorax group (TrxG) protein complex at the Ink4a locus. Knockdown of TrxG complex components, in conjunction with expression of Ezh2, resulted in Ink4a repression and increased replication of ? cells in aged mice. These results indicate that combined modulation of polycomb group proteins, such as EZH2, along with TrxG proteins to repress Ink4a can rejuvenate the replication capacity of aged ? cells. This study provides potential therapeutic targets for expansion of adult ? cell mass.

    View details for DOI 10.1172/JCI69468

    View details for PubMedID 24216481

  • A Molecular Signature for Purified Definitive Endoderm Guides Differentiation and Isolation of Endoderm from Mouse and Human Embryonic Stem Cells STEM CELLS AND DEVELOPMENT Wang, P., McKnight, K. D., Wong, D. J., Rodriguez, R. T., Sugiyama, T., Gu, X., Ghodasara, A., Qu, K., Chang, H. Y., Kim, S. K. 2012; 21 (12): 2273-2287

    Abstract

    Embryonic definitive endoderm (DE) generates the epithelial compartment of vital organs such as liver, pancreas, and intestine. However, purification of DE in mammals has not been achieved, limiting the molecular "definition" of endoderm, and hindering our understanding of DE development and attempts to produce endoderm from sources such as embryonic stem (ES) cells. Here, we describe purification of mouse DE using fluorescence-activated cell sorting (FACS) and mice harboring a transgene encoding enhanced green fluorescent protein (eGFP) inserted into the Sox17 locus, which is expressed in the embryonic endoderm. Comparison of patterns of signaling pathway activation in native mouse DE and endoderm-like cells generated from ES cells produced novel culture modifications that generated Sox17-eGFP? progeny whose gene expression resembled DE more closely than achieved with standard methods. These studies also produced new FACS methods for purifying DE from nontransgenic mice and mouse ES cell cultures. Parallel studies of a new human SOX17-eGFP ES cell line allowed analysis of endoderm differentiation in vitro, leading to culture modifications that enhanced expression of an endoderm-like signature. This work should accelerate our understanding of mechanisms regulating DE development in mice and humans, and guide further use of ES cells for tissue replacement.

    View details for DOI 10.1089/scd.2011.0416

    View details for Web of Science ID 000307295500018

    View details for PubMedID 22236333

  • Deconstructing Pancreas Developmental Biology COLD SPRING HARBOR PERSPECTIVES IN BIOLOGY Benitez, C. M., Goodyer, W. R., Kim, S. K. 2012; 4 (6)

    Abstract

    The relentless nature and increasing prevalence of human pancreatic diseases, in particular, diabetes mellitus and adenocarcinoma, has motivated further understanding of pancreas organogenesis. The pancreas is a multifunctional organ whose epithelial cells govern a diversity of physiologically vital endocrine and exocrine functions. The mechanisms governing the birth, differentiation, morphogenesis, growth, maturation, and maintenance of the endocrine and exocrine components in the pancreas have been discovered recently with increasing tempo. This includes recent studies unveiling mechanisms permitting unexpected flexibility in the developmental potential of immature and mature pancreatic cell subsets, including the ability to interconvert fates. In this article, we describe how classical cell biology, genetic analysis, lineage tracing, and embryological investigations are being complemented by powerful modern methods including epigenetic analysis, time-lapse imaging, and flow cytometry-based cell purification to dissect fundamental processes of pancreas development.

    View details for DOI 10.1101/cshperspect.a012401

    View details for Web of Science ID 000308028500015

    View details for PubMedID 22587935

  • Gut insulin from Foxo1 loss NATURE GENETICS Kim, S. K. 2012; 44 (4): 363-364

    Abstract

    Neuroendocrine cells, including those in the gut, have a vast array of functions. A new study shows that conditional inactivation of the gene encoding Foxo1 in mouse intestinal endocrine cells converts them into cells synthesizing and secreting insulin. Ectopic gut insulin production was sufficient to ameliorate glucose control in mice with conditional pancreatic ?-cell loss and diabetes mellitus.

    View details for DOI 10.1038/ng.2226

    View details for Web of Science ID 000302130600005

    View details for PubMedID 22456735

  • Specification of Drosophila Corpora Cardiaca Neuroendocrine Cells from Mesoderm Is Regulated by Notch Signaling PLOS GENETICS Park, S., Bustamante, E. L., Antonova, J., McLean, G. W., Kim, S. K. 2011; 7 (8)

    Abstract

    Drosophila neuroendocrine cells comprising the corpora cardiaca (CC) are essential for systemic glucose regulation and represent functional orthologues of vertebrate pancreatic ?-cells. Although Drosophila CC cells have been regarded as developmental orthologues of pituitary gland, the genetic regulation of CC development is poorly understood. From a genetic screen, we identified multiple novel regulators of CC development, including Notch signaling factors. Our studies demonstrate that the disruption of Notch signaling can lead to the expansion of CC cells. Live imaging demonstrates localized emergence of extra precursor cells as the basis of CC expansion in Notch mutants. Contrary to a recent report, we unexpectedly found that CC cells originate from head mesoderm. We show that Tinman expression in head mesoderm is regulated by Notch signaling and that the combination of Daughterless and Tinman is sufficient for ectopic CC specification in mesoderm. Understanding the cellular, genetic, signaling, and transcriptional basis of CC cell specification and expansion should accelerate discovery of molecular mechanisms regulating ontogeny of organs that control metabolism.

    View details for DOI 10.1371/journal.pgen.1002241

    View details for Web of Science ID 000294297000036

    View details for PubMedID 21901108

  • Extensive and coordinated transcription of noncoding RNAs within cell-cycle promoters NATURE GENETICS Hung, T., Wang, Y., Lin, M. F., Koegel, A. K., Kotake, Y., Grant, G. D., Horlings, H. M., Shah, N., Umbricht, C., Wang, P., Wang, Y., Kong, B., Langerod, A., Borresen-Dale, A., Kim, S. K., van de Vijver, M., Sukumar, S., Whitfield, M. L., Kellis, M., Xiong, Y., Wong, D. J., Chang, H. Y. 2011; 43 (7): 621-U196

    Abstract

    Transcription of long noncoding RNAs (lncRNAs) within gene regulatory elements can modulate gene activity in response to external stimuli, but the scope and functions of such activity are not known. Here we use an ultrahigh-density array that tiles the promoters of 56 cell-cycle genes to interrogate 108 samples representing diverse perturbations. We identify 216 transcribed regions that encode putative lncRNAs, many with RT-PCR-validated periodic expression during the cell cycle, show altered expression in human cancers and are regulated in expression by specific oncogenic stimuli, stem cell differentiation or DNA damage. DNA damage induces five lncRNAs from the CDKN1A promoter, and one such lncRNA, named PANDA, is induced in a p53-dependent manner. PANDA interacts with the transcription factor NF-YA to limit expression of pro-apoptotic genes; PANDA depletion markedly sensitized human fibroblasts to apoptosis by doxorubicin. These findings suggest potentially widespread roles for promoter lncRNAs in cell-growth control.

    View details for DOI 10.1038/ng.848

    View details for Web of Science ID 000292184600005

    View details for PubMedID 21642992

  • Targeting SOX17 in Human Embryonic Stem Cells Creates Unique Strategies for Isolating and Analyzing Developing Endoderm CELL STEM CELL Wang, P., Rodriguez, R. T., Wang, J., Ghodasara, A., Kim, S. K. 2011; 8 (3): 335-346

    Abstract

    Human embryonic stem cells (hESCs) can provide insights into development of inaccessible human tissues such as embryonic endoderm. Progress in this area has been hindered by a lack of methods for isolating endodermal cells and tracing fates of their differentiated progeny. By using homologous recombination in human ESCs, we inserted an enhanced green fluorescent protein (eGFP) transgene into the SOX17 locus, a postulated marker of human endoderm. FACS purification and gene expression profiling confirmed that SOX17(+)-hESC progeny expressed endodermal markers and unveiled specific cell surface protein combinations that permitted FACS-based isolation of primitive gut tube endodermal cells produced from unmodified human ESCs and from induced pluripotent stem cells (iPSC). Differentiating SOX17(+) endodermal cells expressed markers of liver, pancreas, and intestinal epithelium in vitro and gave rise to endodermal progeny in vivo. Thus, prospective isolation, lineage tracing, and developmental studies of SOX17(+) hESC progeny have revealed fundamental aspects of human endodermal biology.

    View details for DOI 10.1016/j.stem.2011.01.017

    View details for Web of Science ID 000288404400015

    View details for PubMedID 21362573

  • Deconstructing Pancreas Development to Reconstruct Human Islets from Pluripotent Stem Cells CELL STEM CELL McKnight, K. D., Wang, P., Kim, S. K. 2010; 6 (4): 300-308

    Abstract

    There is considerable excitement about harnessing the potential of human stem cells to replace pancreatic islets that are destroyed in type 1 diabetes mellitus. However, our current understanding of the mechanisms underlying pancreas and islet ontogeny has come largely from the powerful genetic, developmental, and embryological approaches available in nonhuman organisms. Successful islet reconstruction from human pluripotent cells will require greater attention to "deconstructing" human pancreas and islet developmental biology and consistent application of conditional genetics, lineage tracing, and cell purification to stem cell biology.

    View details for DOI 10.1016/j.stem.2010.03.003

    View details for Web of Science ID 000276823300009

    View details for PubMedID 20362535

  • Polycomb protein Ezh2 regulates pancreatic beta-cell Ink4a/Arf expression and regeneration in diabetes mellitus GENES & DEVELOPMENT Chen, H., Gu, X., Su, I., Bottino, R., Contreras, J. L., Tarakhovsky, A., Kim, S. K. 2009; 23 (8): 975-985

    Abstract

    Proliferation of pancreatic islet beta cells is an important mechanism for self-renewal and for adaptive islet expansion. Increased expression of the Ink4a/Arf locus, which encodes the cyclin-dependent kinase inhibitor p16(INK4a) and tumor suppressor p19(Arf), limits beta-cell regeneration in aging mice, but the basis of beta-cell Ink4a/Arf regulation is poorly understood. Here we show that Enhancer of zeste homolog 2 (Ezh2), a histone methyltransferase and component of a Polycomb group (PcG) protein complex, represses Ink4a/Arf in islet beta cells. Ezh2 levels decline in aging islet beta cells, and this attrition coincides with reduced histone H3 trimethylation at Ink4a/Arf, and increased levels of p16(INK4a) and p19(Arf). Conditional deletion of beta-cell Ezh2 in juvenile mice also reduced H3 trimethylation at the Ink4a/Arf locus, leading to precocious increases of p16(INK4a) and p19(Arf). These mutant mice had reduced beta-cell proliferation and mass, hypoinsulinemia, and mild diabetes, phenotypes rescued by germline deletion of Ink4a/Arf. beta-Cell destruction with streptozotocin in controls led to increased Ezh2 expression that accompanied adaptive beta-cell proliferation and re-establishment of beta-cell mass; in contrast, mutant mice treated similarly failed to regenerate beta cells, resulting in lethal diabetes. Our discovery of Ezh2-dependent beta-cell proliferation revealed unique epigenetic mechanisms underlying normal beta-cell expansion and beta-cell regenerative failure in diabetes pathogenesis.

    View details for DOI 10.1101/gad.1742509

    View details for Web of Science ID 000265449900010

    View details for PubMedID 19390090

  • Fluorescence-activated cell sorting purification of pancreatic progenitor cells DIABETES OBESITY & METABOLISM Sugiyama, T., Kim, S. K. 2008; 10: 179-185

    Abstract

    Here we review progress on isolation and characterization of progenitor cells in the pancreas. We discuss advantages and current limitations of experiments with purified pancreatic cells, and areas where future growth in our understanding is needed to advance experiments in pancreas biology based on cell purification.

    View details for DOI 10.1111/j.1463-13262008.00954.x

    View details for Web of Science ID 000262726300019

    View details for PubMedID 18834445

  • Characterization of six new human embryonic stem cell lines (HSF7, -8, -9, -10, -12, and -13) derived under minimal-animal component conditions STEM CELLS AND DEVELOPMENT Chavez, S. L., Meneses, J. J., Nguyen, H. N., Kim, S. K., Pera, R. A. 2008; 17 (3): 535-546

    Abstract

    Human embryonic stem cells (hESCs) provide a renewable source of a variety of cell types with the potential for use in both scientific research and clinical cell-based therapy. Several hESC lines have previously been isolated and characterized, however, the majority of these lines were generated in the presence of animal serum and animal-derived feeder cells. Therefore, the exposure of the hESC to animal products may have induced phenotypic and/or genomic changes in the hESC lines not characteristic of normal hESC. Moreover, those hESC lines exposed to animal components may not be used for therapeutic applications due to the risk of graft rejection and pathogenic transmission from animal sources. In this study, we characterized six new hESC lines derived from human blastocysts under minimal-animal component conditions and cultured with human fetal lung fibroblasts. The hESC lines retained the ability to self-renew, are karytopically normal, and express stage-specific embryonic antigen-3 (SSEA-3), SSEA-4, TRA-1-60, and TRA-1-81, but not SSEA-1, markers of pluripotent hESC. In addition, we show that telomerase activity decreased in each of the hESC lines following differentiation into embryoid bodies, albeit to different degrees. Finally, we demonstrate that the hESC lines are capable of differentiating into the three embryonic germ layers in vitro and form complex teratomas in vivo. This suggests that the hESC lines described here are valuable models for both future in vitro and in vivo studies, which may aid in the progression toward clinical-grade cell therapy.

    View details for DOI 10.1089/scd.2007.0216

    View details for Web of Science ID 000257115600014

    View details for PubMedID 18513167

  • Menin controls growth of pancreatic beta-cells in pregnant mice and promotes gestational diabetes mellitus SCIENCE Karnik, S. K., Chen, H., McLean, G. W., Heit, J. J., Gu, X., Zhang, A. Y., Fontaine, M., Yen, M. H., Kim, S. K. 2007; 318 (5851): 806-809

    Abstract

    During pregnancy, maternal pancreatic islets grow to match dynamic physiological demands, but the mechanisms regulating adaptive islet growth in this setting are poorly understood. Here we show that menin, a protein previously characterized as an endocrine tumor suppressor and transcriptional regulator, controls islet growth in pregnant mice. Pregnancy stimulated proliferation of maternal pancreatic islet beta-cells that was accompanied by reduced islet levels of menin and its targets. Transgenic expression of menin in maternal beta-cells prevented islet expansion and led to hyperglycemia and impaired glucose tolerance, hallmark features of gestational diabetes. Prolactin, a hormonal regulator of pregnancy, repressed islet menin levels and stimulated beta-cell proliferation. These results expand our understanding of mechanisms underlying diabetes pathogenesis and reveal potential targets for therapy in diabetes.

    View details for DOI 10.1126/science.1146812

    View details for Web of Science ID 000250583900043

    View details for PubMedID 17975067

  • Menin-mediated caspase 8 expression in suppressing multiple endocrine neoplasia type 1 JOURNAL OF BIOLOGICAL CHEMISTRY La, P., Yang, Y., Karnik, S. K., Silva, A. C., Schnepp, R. W., Kim, S. K., Hua, X. 2007; 282 (43): 31332-31340

    Abstract

    Multiple endocrine neoplasia type 1 (MEN1) is a familial tumor syndrome linked to mutation of the MEN1 gene, which encodes a tumor suppressor, menin. We previously reported that menin up-regulates the caspase 8 expression and promotes TNF-alpha-induced apoptosis. However, it remains unclear how menin up-regulates caspase 8 expression and whether menin-mediated caspase 8 expression plays a role in repressing MEN1 development. Here we show that menin binds the 5'-untranslated region (5'-UTR) of the Caspase 8 locus in vivo and activates transcription of a reporter gene through the 5'-UTR. Menin directly binds the 5'-UTR in a sequence-independent manner in vitro. Moreover, Men1 ablation in cells reduces acetylation of histones H3 and H4 at the 5'-UTR of the caspase 8 locus bound by menin in vivo. Notably, the MEN1-derived menin point mutants lose their ability to bind the caspase 8 locus and fail to induce caspase 8 expression and TNF-alpha-mediated apoptosis. Consistent with these observations, the expression level of caspase 8 is markedly reduced in insulinomas from Men1(+/-) mice. Together, our results indicate that menin enhances the caspase 8 expression by binding the caspase 8 locus, and suggest that menin suppresses MEN1 tumorigenesis, at least in part, by up-regulating caspase 8 expression.

    View details for DOI 10.1074/jbc.M609555200

    View details for Web of Science ID 000250309200022

    View details for PubMedID 17766243

  • Glucose infusion in mice - A new model to induce beta-cell replication DIABETES Alonso, L. C., Yokoe, T., Zhang, P., Scott, D. K., Kim, S. K., O'Donnell, C. P., Garcia-Ocana, A. 2007; 56 (7): 1792-1801

    Abstract

    Developing new techniques to induce beta-cells to replicate is a major goal in diabetes research. Endogenous beta-cells replicate in response to metabolic changes, such as obesity and pregnancy, which increase insulin requirement. Mouse genetic models promise to reveal the pathways responsible for compensatory beta-cell replication. However, no simple, short-term, physiological replication stimulus exists to test mouse models for compensatory replication. Here, we present a new tool to induce beta-cell replication in living mice. Four-day glucose infusion is well tolerated by mice as measured by hemodynamics, body weight, organ weight, food intake, and corticosterone level. Mild sustained hyperglycemia and hyperinsulinemia induce a robust and significant fivefold increase in beta-cell replication. Glucose-induced beta-cell replication is dose and time dependent. Beta-cell mass, islet number, beta-cell size, and beta-cell death are not altered by glucose infusion over this time frame. Glucose infusion increases both the total protein abundance and nuclear localization of cyclin D2 in islets, which has not been previously reported. Thus, we have developed a new model to study the regulation of compensatory beta-cell replication, and we describe important novel characteristics of mouse beta-cell responses to glucose in the living pancreas.

    View details for DOI 10.2337/db06-1513

    View details for Web of Science ID 000247768000005

    View details for PubMedID 17400928

  • Wnt signaling regulates pancreatic beta cell proliferation PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Rulifson, I. C., Karnik, S. K., Heiser, P. W., Ten Berge, D., Chen, H., Gu, X., Taketo, M. M., Nusse, R., Hebrok, M., Kim, S. K. 2007; 104 (15): 6247-6252

    Abstract

    There is widespread interest in defining factors and mechanisms that stimulate proliferation of pancreatic islet cells. Wnt signaling is an important regulator of organ growth and cell fates, and genes encoding Wnt-signaling factors are expressed in the pancreas. However, it is unclear whether Wnt signaling regulates pancreatic islet proliferation and differentiation. Here we provide evidence that Wnt signaling stimulates islet beta cell proliferation. The addition of purified Wnt3a protein to cultured beta cells or islets promoted expression of Pitx2, a direct target of Wnt signaling, and Cyclin D2, an essential regulator of beta cell cycle progression, and led to increased beta cell proliferation in vitro. Conditional pancreatic beta cell expression of activated beta-catenin, a crucial Wnt signal transduction protein, produced similar phenotypes in vivo, leading to beta cell expansion, increased insulin production and serum levels, and enhanced glucose handling. Conditional beta cell expression of Axin, a potent negative regulator of Wnt signaling, led to reduced Pitx2 and Cyclin D2 expression by beta cells, resulting in reduced neonatal beta cell expansion and mass and impaired glucose tolerance. Thus, Wnt signaling is both necessary and sufficient for islet beta cell proliferation, and our study provides previously unrecognized evidence of a mechanism governing endocrine pancreas growth and function.

    View details for DOI 10.1073/pnas.0701509104

    View details for Web of Science ID 000245737500029

    View details for PubMedID 17404238

  • Conserved markers of fetal pancreatic epithelium permit prospective isolation of islet progenitor cells by FACS PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Sugiyama, T., Rodriguez, R. T., McLean, G. W., Kim, S. K. 2007; 104 (1): 175-180

    Abstract

    Prospective isolation and characterization of progenitor cells is a paradigmatic strategy for studies of organ development. However, extraction of viable cells, fractionation of lineages, and in vitro analysis of progenitors from the fetal pancreas in experimental organisms like mice has proved challenging and has not yet been reported for human fetal pancreas. Here, we report isolation of pancreatic islet progenitor cells from fetal mice by FACS. Monoclonal antibodies that recognize cell-surface proteins on candidate stem cells in brain, skin, and other organs enabled separation of major pancreatic cell lineages and isolation of native pancreatic cells expressing neurogenin 3, an established marker of islet progenitors. New in vitro cell culture methods permitted isolated mouse islet progenitors to develop into hormone-expressing endocrine cells. Insulin-producing cells derived in vitro required or expressed factors that regulate fetal beta cell differentiation; thus, the genetic programs normally controlling in vivo mouse islet development are similarly required in our system. Moreover, antibodies that recognize conserved orthologous cell-surface epitopes in human fetal pancreas allowed FACS-based enrichment of candidate islet progenitor cells expressing neurogenin 3. Our studies reveal previously undescribed strategies for prospective purification and analysis of pancreatic endocrine progenitor cells that should accelerate studies of islet development and replacement.

    View details for DOI 10.1073/pnas.0609490104

    View details for Web of Science ID 000243456300033

    View details for PubMedID 17190805

  • The ATP-sensitive potassium (K-ATP) channel-encoded dSUR gene is required for Drosophila heart function and is regulated by tinman PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Akasaka, T., Klinedinst, S., Ocorr, K., Bustamante, E. L., Kim, S. K., Bodmer, R. 2006; 103 (32): 11999-12004

    Abstract

    The homeobox transcription factor Tinman plays an important role in the initiation of heart development. Later functions of Tinman, including the target genes involved in cardiac physiology, are less well studied. We focused on the dSUR gene, which encodes an ATP-binding cassette transmembrane protein that is expressed in the heart. Mammalian SUR genes are associated with K(ATP) (ATP-sensitive potassium) channels, which are involved in metabolic homeostasis. We provide experimental evidence that Tinman directly regulates dSUR expression in the developing heart. We identified a cis-regulatory element in the first intron of dSUR, which contains Tinman consensus binding sites and is sufficient for faithful dSUR expression in the fly's myocardium. Site-directed mutagenesis of this element shows that these Tinman sites are critical to dSUR expression, and further genetic manipulations suggest that the GATA transcription factor Pannier is synergistically involved in cardiac-restricted dSUR expression in vivo. Physiological analysis of dSUR knock-down flies supports the idea that dSUR plays a protective role against hypoxic stress and pacing-induced heart failure. Because dSUR expression dramatically decreases with age, it is likely to be a factor involved in the cardiac aging phenotype of Drosophila. dSUR provides a model for addressing how embryonic regulators of myocardial cell commitment can contribute to the establishment and maintenance of cardiac performance.

    View details for DOI 10.1073/pnas.0603098103

    View details for Web of Science ID 000239701900033

    View details for PubMedID 16882722

  • NFAT dysregulation by increased dosage of DSCR1 and DYRK1A on chromosome 21 NATURE Arron, J. R., Winslow, M. M., Polleri, A., Chang, C., Wu, H., Gao, X., Neilson, J. R., Chen, L., Heit, J. J., Kim, S. K., Yamasaki, N., Miyakawa, T., Francke, U., Graef, I. A., Crabtree, G. R. 2006; 441 (7093): 595-600

    Abstract

    Trisomy 21 results in Down's syndrome, but little is known about how a 1.5-fold increase in gene dosage produces the pleiotropic phenotypes of Down's syndrome. Here we report that two genes, DSCR1 and DYRK1A , lie within the critical region of human chromosome 21 and act synergistically to prevent nuclear occupancy of NFATc transcription factors, which are regulators of vertebrate development. We use mathematical modelling to predict that autoregulation within the pathway accentuates the effects of trisomy of DSCR1 and DYRK1A, leading to failure to activate NFATc target genes under specific conditions. Our observations of calcineurin-and Nfatc-deficient mice, Dscr1- and Dyrk1a-overexpressing mice, mouse models of Down's syndrome and human trisomy 21 are consistent with these predictions. We suggest that the 1.5-fold increase in dosage of DSCR1 and DYRK1A cooperatively destabilizes a regulatory circuit, leading to reduced NFATc activity and many of the features of Down's syndrome. More generally, these observations suggest that the destabilization of regulatory circuits can underlie human disease.

    View details for DOI 10.1038/nature04678

    View details for Web of Science ID 000237920800038

    View details for PubMedID 16554754

  • Conditional expression of Smad7 in pancreatic beta cells disrupts TGF-beta signaling and induces reversible diabetes mellitus PLOS BIOLOGY Smart, N. G., Apelqvist, A. A., Gu, X. Y., Harmon, E. B., Topper, J. N., MACDONALD, R. J., Kim, S. K. 2006; 4 (2): 200-209

    Abstract

    Identification of signaling pathways that maintain and promote adult pancreatic islet functions will accelerate our understanding of organogenesis and improve strategies for treating diseases like diabetes mellitus. Previous work has implicated transforming growth factor-beta (TGF-beta) signaling as an important regulator of pancreatic islet development, but has not established whether this signaling pathway is required for essential islet functions in the adult pancreas. Here we describe a conditional system for expressing Smad7, a potent inhibitor of TGF-beta signaling, to identify distinct roles for this pathway in adult and embryonic beta cells. Smad7 expression in Pdx1+ embryonic pancreas cells resulted in striking embryonic beta cell hypoplasia and neonatal lethality. Conditional expression of Smad7 in adult Pdx1+ cells reduced detectable beta cell expression of MafA, menin, and other factors that regulate beta cell function. Reduced pancreatic insulin content and hypoinsulinemia produced overt diabetes that was fully reversed upon resumption of islet TGF-beta signaling. Thus, our studies reveal that TGF-beta signaling is crucial for establishing and maintaining defining features of mature pancreatic beta cells.

    View details for DOI 10.1371/journal.pbio.0040039

    View details for Web of Science ID 000235342900007

    View details for PubMedID 16435884

  • Intrinsic regulators of pancreatic beta-cell proliferation ANNUAL REVIEW OF CELL AND DEVELOPMENTAL BIOLOGY Heit, J. J., Karnik, S. K., Kim, S. K. 2006; 22: 311-338

    Abstract

    Once thought incapable of significant proliferation, the pancreatic beta-cell has recently been shown to harbor immense powers of self-renewal. Pancreatic beta-cells, the sole source of insulin in vertebrate animals, can grow facultatively to a degree unmatched by other organs in experimental animals. beta-cell growth matches changes in systemic insulin demand, which increase during common physiologic states such as aging, obesity, and pregnancy. Compensatory changes in beta-cell mass are controlled by beta-cell proliferation. Here we review recent advances in our understanding of the intrinsic factors and mechanisms that control beta-cell cycle progression. Dysregulation of beta-cell proliferation is emerging as a fundamental feature in the pathogenesis of human disease states such as cancer and diabetes mellitus. New experimental observations and studies of these diseases suggest that beta-cell fate and expansion are coordinately regulated. We speculate on how these advances may accelerate the discovery of new strategies for the treatment of diseases characterized by a deficiency or excess of beta-cells.

    View details for DOI 10.1146/annurev.cellbio.22.010305.104425

    View details for Web of Science ID 000242325100014

    View details for PubMedID 16824015

  • Menin regulates pancreatic islet growth by promoting histone methylation and expression of genes encoding p27(Kip1) and p18(INK4c) PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Karnik, S. K., Hughes, C. M., Gu, X. Y., Rozenblatt-Rosen, O., McLean, G. W., Xiong, Y., Meyerson, M., Kim, S. K. 2005; 102 (41): 14659-14664

    Abstract

    Menin, the product of the Men1 gene mutated in familial multiple endocrine neoplasia type 1 (MEN1), regulates transcription in differentiated cells. Menin associates with and modulates the histone methyltransferase activity of a nuclear protein complex to activate gene expression. However, menin-dependent histone methyltransferase activity in endocrine cells has not been demonstrated, and the mechanism of endocrine tumor suppression by menin remains unclear. Here, we show that menin-dependent histone methylation maintains the in vivo expression of cyclin-dependent kinase (CDK) inhibitors to prevent pancreatic islet tumors. In vivo expression of CDK inhibitors, including p27 and p18, and other cell cycle regulators is disrupted in mouse islet tumors lacking menin. Chromatin immunoprecipitation studies reveal that menin directly associates with regions of the p27 and p18 promoters and increases methylation of lysine 4 (Lys-4) in histone H3 associated with these promoters. Moreover, H3 Lys-4 methylation associated with p27 and p18 is reduced in islet tumors from Men1 mutant mice. Thus, H3 Lys-4 methylation is a crucial function of menin in islet tumor suppression. These studies suggest an epigenetic mechanism of tumor suppression: by promoting histone modifications, menin maintains transcription at multiple loci encoding cell cycle regulators essential for endocrine growth control.

    View details for DOI 10.1073/pnas.0503484102

    View details for Web of Science ID 000232603600034

    View details for PubMedID 16195383

  • Differentiation of insulin-producing cells from human neural progenitor cells PLOS MEDICINE Hori, Y., Gu, X. Y., Xie, X. D., Kim, S. K. 2005; 2 (4): 347-356

    Abstract

    Success in islet-transplantation-based therapies for type 1 diabetes, coupled with a worldwide shortage of transplant-ready islets, has motivated efforts to develop renewable sources of islet-replacement tissue. Islets and neurons share features, including common developmental programs, and in some species brain neurons are the principal source of systemic insulin.Here we show that brain-derived human neural progenitor cells, exposed to a series of signals that regulate in vivo pancreatic islet development, form clusters of glucose-responsive insulin-producing cells (IPCs). During in vitro differentiation of neural progenitor cells with this novel method, genes encoding essential known in vivo regulators of pancreatic islet development were expressed. Following transplantation into immunocompromised mice, IPCs released insulin C-peptide upon glucose challenge, remained differentiated, and did not form detectable tumors.Production of IPCs solely through extracellular factor modulation in the absence of genetic manipulations may promote strategies to derive transplantable islet-replacement tissues from human neural progenitor cells and other types of multipotent human stem cells.

    View details for DOI 10.1371/journal.pmed.0020103

    View details for Web of Science ID 000229163300017

    View details for PubMedID 15839736

  • GDF11 modulates NGN3(+) islet progenitor cell number and promotes beta-cell differentiation in pancreas development DEVELOPMENT Harmon, E. B., Apelqvist, A. A., Smart, N. G., Gu, X. Y., Osborne, D. H., Kim, S. K. 2004; 131 (24): 6163-6174

    Abstract

    Identification of endogenous signals that regulate expansion and maturation of organ-specific progenitor cells is a major goal in studies of organ development. Here we provide evidence that growth differentiation factor 11 (GDF11), a member of the TGF-beta ligand family, governs the number and maturation of islet progenitor cells in mouse pancreas development. Gdf11 is expressed in embryonic pancreatic epithelium during formation of islet progenitor cells that express neurogenin 3. Mice deficient for Gdf11 harbor increased numbers of NGN3+ cells, revealing that GDF11 negatively regulates production of islet progenitor cells. Despite a marked expansion of these NGN3+ islet progenitors, mice lacking Gdf11 have reduced beta-cell numbers and evidence of arrested beta-cell development, indicating that GDF11 is also required for beta-cell maturation. Similar precursor and islet cell phenotypes are observed in mice deficient for SMAD2, an intracellular signaling factor activated by TGF-beta signals. Our data suggest that Gdf11 and Smad2 regulate islet cell differentiation in parallel to the Notch pathway, which previously has been shown to control development of NGN3+ cells. Thus, our studies reveal mechanisms by which GDF11 regulates the production and maturation of islet progenitor cells in pancreas development.

    View details for DOI 10.1242/dev.01535

    View details for Web of Science ID 000226324200014

    View details for PubMedID 15548585

  • Embryonic stem cells and islet replacement in diabetes mellitus PEDIATRIC DIABETES Heit, J. J., Kim, S. K. 2004; 5: 5-15

    Abstract

    Transplantation of functional islets of Langerhans may emerge as a useful therapy for some patients with type 1 diabetes mellitus (DM), but donor islet shortages motivate the search for new sources of transplantable islets. Pluripotent embryonic stem (ES) cells are expandable in culture and have the potential to give rise to all cell types in the body. The recent isolation of pluripotent ES cells from humans has generated excitement over the possibility of engineering glucose-responsive islet replacement tissue from these cells in large quantities. In this study, we review the recent advances in generating insulin-producing cells (IPC) from mouse and human ES (hES) cells.

    View details for Web of Science ID 000226386200003

    View details for PubMedID 15601369

  • Growth inhibitors promote differentiation of insulin-producing tissue from embryonic stem cells PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Hori, Y., Rulifson, I. C., Tsai, B. C., Heit, J. J., Cahoy, J. D., Kim, S. K. 2002; 99 (25): 16105-16110

    Abstract

    The use of embryonic stem cells for cell-replacement therapy in diseases like diabetes mellitus requires methods to control the development of multipotent cells. We report that treatment of mouse embryonic stem cells with inhibitors of phosphoinositide 3-kinase, an essential intracellular signaling regulator, produced cells that resembled pancreatic beta cells in several ways. These cells aggregated in structures similar, but not identical, to pancreatic islets of Langerhans, produced insulin at levels far greater than previously reported, and displayed glucose-dependent insulin release in vitro. Transplantation of these cell aggregates increased circulating insulin levels, reduced weight loss, improved glycemic control, and completely rescued survival in mice with diabetes mellitus. Graft removal resulted in rapid relapse and death. Graft analysis revealed that transplanted insulin-producing cells remained differentiated, enlarged, and did not form detectable tumors. These results provide evidence that embryonic stem cells can serve as the source of insulin-producing replacement tissue in an experimental model of diabetes mellitus. Strategies for producing cells that can replace islet functions described here can be adapted for similar uses with human cells.

    View details for DOI 10.1073/pnas.252618999

    View details for Web of Science ID 000179783400052

    View details for PubMedID 12441403

  • Signaling and transcriptional control of pancreatic organogenesis CURRENT OPINION IN GENETICS & DEVELOPMENT Kim, S. K., MacDonald, R. J. 2002; 12 (5): 540-547

    Abstract

    The results of several new studies encourage a revision of fundamental hypotheses concerning the cellular and molecular mechanisms underlying pancreatic morphogenesis and cell differentiation in the embryo. The roles of FGF- and BMP-signaling indicate a fundamental difference in the induction of the dorsal and the ventral pancreatic anlage. Final commitment to the pancreatic fate requires the action of several transcriptional regulators including IPF1/PDX1, PBX1 and PTF1-P48 after the onset of pancreatic bud formation. Two, largely independent endocrine cell lineages develop during the formation of the embryonic pancreas. Lineage tracing has begun to refine our understanding of the origins of the acinar, ductal and islet cells.

    View details for Web of Science ID 000177898200007

    View details for PubMedID 12200159

  • Ablation of insulin-producing neurons in flies: Growth and diabetic phenotypes SCIENCE Rulifson, E. J., Kim, S. K., Nusse, R. 2002; 296 (5570): 1118-1120

    Abstract

    In the fruit fly Drosophila, four insulin genes are coexpressed in small clusters of cells [insulin-producing cells (IPCs)] in the brain. Here, we show that ablation of these IPCs causes developmental delay, growth retardation, and elevated carbohydrate levels in larval hemolymph. All of the defects were reversed by ectopic expression of a Drosophila insulin transgene. On the basis of these functional data and the observation that IPCs release insulin into the circulatory system, we conclude that brain IPCs are the main systemic supply of insulin during larval growth. We propose that IPCs and pancreatic islet beta cells are functionally analogous and may have evolved from a common ancestral insulin-producing neuron. Interestingly, the phenotype of flies lacking IPCs includes certain features of diabetes mellitus.

    View details for Web of Science ID 000175565000053

    View details for PubMedID 12004130

  • Pbx1 inactivation disrupts pancreas development and in Ipf1-deficient mice promotes diabetes mellitus NATURE GENETICS Kim, S. K., SELLERI, L., Lee, J. S., Zhang, A. Y., Gu, X. Y., Jacobs, Y., Cleary, M. L. 2002; 30 (4): 430-435

    Abstract

    Pbx1 is a member of the TALE (three-amino acid loop extension) class of homeodomain transcription factors, which are components of hetero-oligomeric protein complexes thought to regulate developmental gene expression and to maintain differentiated cell states. In vitro studies have shown that Pbx1 regulates the activity of Ipf1 (also known as Pdx1), a ParaHox homeodomain transcription factor required for the development and function of the pancreas in mice and humans. To investigate in vivo roles of Pbx1 in pancreatic development and function, we examined pancreatic Pbx1 expression, and morphogenesis, cell differentiation and function in mice deficient for Pbx1. Pbx1-/- embryos had pancreatic hypoplasia and marked defects in exocrine and endocrine cell differentiation prior to death at embryonic day (E) 15 or E16. In these embryos, expression of Isl1 and Atoh5, essential regulators of pancreatic morphogenesis and differentiation, was severely reduced. Pbx1+/- adults had pancreatic islet malformations, impaired glucose tolerance and hypoinsulinemia. Thus, Pbx1 is essential for normal pancreatic development and function. Analysis of trans-heterozygous Pbx1+/- Ipf1+/- mice revealed in vivo genetic interactions between Pbx1 and Ipf1 that are essential for postnatal pancreatic function; these mice developed age-dependent overt diabetes mellitus, unlike Pbx1+/- or Ipf1+/- mice. Mutations affecting the Ipf1 protein may promote diabetes mellitus in mice and humans. This study suggests that perturbation of Pbx1 activity may also promote susceptibility to diabetes mellitus.

    View details for DOI 10.1038/ng860

    View details for Web of Science ID 000174682000023

    View details for PubMedID 11912494

  • Hedgehog signaling in gastrointestinal development and disease. Current molecular medicine Harmon, E. B., Ko, A. H., Kim, S. K. 2002; 2 (1): 67-82

    Abstract

    The development of the gastrointestinal (GI) tract and its associated parenchymal organs depends on Hedgehog signals from the endoderm to the surrounding mesoderm. During development, Hedgehog signaling is essential for patterning the GI tract along anterior-posterior (A-P), dorsal-ventral (D-V), and radial axes, as well as in maintenance of stem cells. Our knowledge about these roles for Hedgehog signaling is derived from studies of developmental defects that result from disrupted or activated Hedgehog signaling in model organisms including mouse, chick, and frog. These studies provide evidence for distinct roles of specific Hedgehog ligands in GI development. Studies in model organisms have also elucidated how Hedgehog signaling may function in development and function of the GI tract in humans. Several diseases and congenital syndromes are known to result from genetic defects in Hedgehog signaling components, and this pathway may ultimately prove to be an important target for future diagnostic and therapeutic tools.

    View details for PubMedID 11898849

  • Pancreatic islet cell replacement - Successes and opportunities REPARATIVE MEDICINE: GROWING TISSUES AND ORGANS Kim, S. K. 2002; 961: 41-43

    View details for Web of Science ID 000177134500005

    View details for PubMedID 12081860

  • Intercellular signals regulating pancreas development and function GENES & DEVELOPMENT Kim, S. K., Hebrok, M. 2001; 15 (2): 111-127

    View details for Web of Science ID 000166683800001

    View details for PubMedID 11157769

  • Regulation of pancreas development by hedgehog signaling DEVELOPMENT Hebrok, M., Kim, S. K., St-Jacques, B., MCMAHON, A. P., Melton, D. A. 2000; 127 (22): 4905-4913

    Abstract

    Pancreas organogenesis is regulated by the interaction of distinct signaling pathways that promote or restrict morphogenesis and cell differentiation. Previous work has shown that activin, a TGF(beta+) signaling molecule, permits pancreas development by repressing expression of Sonic hedgehog (Shh), a member of the hedgehog family of signaling molecules that antagonize pancreas development. Here we show that Indian hedgehog (Ihh), another hedgehog family member, and Patched 1 (Ptc1), a receptor and negative regulator of hedgehog activity, are expressed in pancreatic tissue. Targeted inactivation of Ihh in mice allows ectopic branching of ventral pancreatic tissue resulting in an annulus that encircles the duodenum, a phenotype frequently observed in humans suffering from a rare disorder known as annular pancreas. Shh(-)(/)(-) and Shh(-)(/)(-) Ihh(+/)(-) mutants have a threefold increase in pancreas mass, and a fourfold increase in pancreatic endocrine cell numbers. In contrast, mutations in Ptc1 reduce pancreas gene expression and impair glucose homeostasis. Thus, islet cell, pancreatic mass and pancreatic morphogenesis are regulated by hedgehog signaling molecules expressed within and adjacent to the embryonic pancreas. Defects in hedgehog signaling may lead to congenital pancreatic malformations and glucose intolerance.

    View details for Web of Science ID 000165754100015

    View details for PubMedID 11044404

  • Activin receptor patterning of foregut organogenesis GENES & DEVELOPMENT Kim, S. K., Hebrok, M., Li, E., Oh, S. P., Schrewe, H., Harmon, E. B., Lee, J. S., Melton, D. A. 2000; 14 (15): 1866-1871

    Abstract

    Foregut development produces a characteristic sequence of gastrointestinal and respiratory organs, but the signaling pathways that ensure this developmental order remain largely unknown. Here, mutations of activin receptors ActRIIA and ActRIIB are shown to disrupt the development of posterior foregut-derived organs, including the stomach, pancreas, and spleen. Foregut expression of genes including Shh and Isl1 is shifted in mutant mice. The endocrine pancreas is particularly sensitive to the type and extent of receptor inactivation. ActRIIA(+/-)B(+/-) animals lack axial defects, but have hypoplastic pancreatic islets, hypoinsulinemia, and impaired glucose tolerance. Thus, activin receptor-mediated signaling regulates axial patterning, cell differentiation, and function of foregut-derived organs.

    View details for Web of Science ID 000088640100003

    View details for PubMedID 10921901

  • Screening for novel pancreatic genes expressed during embryogenesis DIABETES Hebrok, M., Kim, S. K., Melton, D. A. 1999; 48 (8): 1550-1556

    Abstract

    We have combined suppressive subtractive hybridization with in situ hybridization to identify genes expressed at early stages of pancreas development. By using polymerase chain reaction amplification and subtractive hybridization, this protocol for screening can be applied when the amount of RNA is limited. Seven genes expressed in or adjacent to the pancreas anlage were isolated, three of which show similarity to known genes. The expression pattern and sequence information indicate that some of the genes could govern pancreas development.

    View details for Web of Science ID 000081577400008

    View details for PubMedID 10426372

  • Pancreas development is promoted by cyclopamine, a Hedgehog signaling inhibitor PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Kim, S. K., Melton, D. A. 1998; 95 (22): 13036-13041

    Abstract

    Exposure to cyclopamine, a steroid alkaloid that blocks Sonic hedgehog (Shh) signaling, promotes pancreatic expansion in embryonic chicks. Heterotopic development of pancreatic endocrine and exocrine structures occurs in regions adjacent to the pancreas including stomach and duodenum, and insulin-producing islets in the pancreas are enlarged. The homeodomain transcription factor PDX1, required for pancreas development, is expressed broadly in the posterior foregut but pancreas development normally initiates only in a restricted region of PDX1-expressing posterior foregut where endodermal Shh expression is repressed. The results suggests that cyclopamine expands the endodermal region where Shh signaling does not occur, resulting in pancreatic differentiation in a larger region of PDX1-expressing foregut endoderm. Cyclopamine reveals the capacity of a broad region of the posterior embryonic foregut to form pancreatic cells and provides a means for expanding embryonic pancreas development.

    View details for Web of Science ID 000076757300058

    View details for PubMedID 9789036

  • Notochord repression of endodermal Sonic hedgehog permits pancreas development GENES & DEVELOPMENT Hebrok, M., Kim, S. K., Melton, D. A. 1998; 12 (11): 1705-1713

    Abstract

    Notochord signals to the endoderm are required for development of the chick dorsal pancreas. Sonic hedgehog (SHH) is normally absent from pancreatic endoderm, and we provide evidence that notochord, in contrast to its effects on adjacent neuroectoderm where SHH expression is induced, represses SHH expression in adjacent nascent pancreatic endoderm. We identify activin-betaB and FGF2 as notochord factors that can repress endodermal SHH and thereby permit expression of pancreas genes including Pdx1 and insulin. Endoderm treatment with antibodies that block hedgehog activity also results in pancreatic gene expression. Prevention of SHH expression in prepancreatic dorsal endoderm by intercellular signals, like activin and FGF, may be critical for permitting early steps of chick pancreatic development.

    View details for Web of Science ID 000074149000013

    View details for PubMedID 9620856

  • Notochord to endoderm signaling is required for pancreas development DEVELOPMENT Kim, S. K., Hebrok, M., Melton, D. A. 1997; 124 (21): 4243-4252

    Abstract

    The role of the notochord in inducing and patterning adjacent neural and mesodermal tissues is well established. We provide evidence that the notochord is also required for one of the earliest known steps in the development of the pancreas, an endodermally derived organ. At a developmental stage in chick embryos when the notochord touches the endoderm, removal of notochord eliminates subsequent expression of several markers of dorsal pancreas bud development, including insulin, glucagon and carboxypeptidase A. Pancreatic gene expression can be initiated and maintained in prepancreatic chick endoderm grown in vitro with notochord. Non-pancreatic endoderm, however, does not express pancreatic genes when recombined with the same notochord. The results suggest that the notochord provides a permissive signal to endoderm to specify pancreatic fate in a stepwise manner.

    View details for Web of Science ID A1997YG86200007

    View details for PubMedID 9334273

  • Pancreas development in the chick embryo COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY Kim, S. K., Hebrok, M., Melton, D. A. 1997; 62: 377-383

    View details for Web of Science ID 000073570200044

    View details for PubMedID 9598372

  • Chemotherapy and neutropenia HEMATOLOGY-ONCOLOGY CLINICS OF NORTH AMERICA Kim, S. K., Demetri, G. D. 1996; 10 (2): 377-?

    Abstract

    Myelosuppression is the most common toxicity associated with the administration of dose-intensive cytotoxic chemotherapy. The basic understanding of neutrophil biology and the physiology of chemotherapy-induced neutropenia has advanced tremendously in the past 2 decades. Concordantly, the ability to reduce the morbidity associated with neutropenia has improved. Adjunctive cytokine and progenitor cell support of hematologic recovery after myelosuppressive therapy have proved to be models of translational research and have led to novel therapeutic initiatives for patients with cancer and hematologic malignancies. In this article, fundamental aspects of neutrophil production are discussed, and the clinical development of hematopoietic cytokines active on cells of the leukocyte lineages is presented.

    View details for Web of Science ID A1996UC64900006

    View details for PubMedID 8707761

  • CONTROL OF CELL-DENSITY AND PATTERN BY INTERCELLULAR SIGNALING IN MYXOCOCCUS DEVELOPMENT ANNUAL REVIEW OF MICROBIOLOGY Kim, S. K., Kaiser, D., Kuspa, A. 1992; 46: 117-139

    Abstract

    Myxococcus xanthus cells feed, move, and develop cooperatively. Genetic, biochemical, and cell mosaic studies demonstrate that cells coordinate their multicellular behavior by transmission of intercellular signals. Starvation for amino acids at sufficiently high density on a solid surface initiates a series of events culminating in the formation of a multicellular structure called a fruiting body filled with dormant, environmentally resistant spores. This review discusses how myxobacteria use extracellular signals to sequentially check the density and arrangement of cells at different stages during development. For at least one early and one late developmental signal, cell density determines the efficiency of intercellular signaling. In turn, proper signaling insures that the appropriate cell density exists, thus controlling the progress of multicellular development in M. xanthus.

    View details for Web of Science ID A1992JQ92900005

    View details for PubMedID 1444251

  • INTERCELLULAR SIGNALING IN MYXOCOCCUS DEVELOPMENT - THE ROLE OF C-FACTOR TRENDS IN GENETICS Kim, S. K. 1991; 7 (11-12): 361-365

    Abstract

    Cell communication governs differentiation and morphogenesis in fruiting body formation by Myxococcus xanthus. Transmission of a small short-range intercellular signal by a protein called C factor directs multicellular pattern formation and coordinates the timing of major developmental events.

    View details for Web of Science ID A1991GN92700005

    View details for PubMedID 1668187

  • C-FACTOR HAS DISTINCT AGGREGATION AND SPORULATION THRESHOLDS DURING MYXOCOCCUS DEVELOPMENT JOURNAL OF BACTERIOLOGY Kim, S. K., Kaiser, D. 1991; 173 (5): 1722-1728

    Abstract

    C-factor, the protein product of the csgA gene, acts as a short-range morphogenetic signal. It is required for fruiting body development of the gram-negative bacterium Myxococcus xanthus. Aggregation, sporulation, and expression of a set of genes that are C-factor dependent, all of which fail in csgA mutant cells, are completely restored by addition of purified C-factor. We report here that, depending on its concentration, C-factor can elicit two distinct morphogenetic and transcriptional responses from csgA cells. Low levels of C-factor bring about aggregation and expression of an early C-dependent gene, whereas higher levels lead to the same effects plus expression of a late C-dependent gene and spore formation. C-factor positively regulates its own transcription. An approximately fourfold net increase in csgA transcription and C-factor levels during development was measured. We propose that autoregulation and the two distinct activity thresholds allow C-factor to act as a timer, first triggering aggregation, then sporulation, thereby producing the appropriate developmental order.

    View details for Web of Science ID A1991EZ17000022

    View details for PubMedID 1847908

  • CELL ALIGNMENT REQUIRED IN DIFFERENTIATION OF MYXOCOCCUS-XANTHUS SCIENCE Kim, S. K., Kaiser, D. 1990; 249 (4971): 926-928

    Abstract

    During fruiting body morphogenesis of Myxococcus xanthus, cell movement is required for transmission of C-factor, a short range intercellular signaling protein necessary for sporulation and developmental gene expression. Nonmotile cells fail to sporulate and to express C-factor-dependent genes, but both defects were rescued by a simple manipulation of cell position that oriented the cells in aligned, parallel groups. A similar pattern of aligned cells normally results from coordinated recruitment of wildtype cells into multicellular aggregates, which later form mature fruiting bodies. It is proposed that directed cell movement establishes critical contacts between adjacent cells, which are required for efficient intercellular C-factor transmission.

    View details for Web of Science ID A1990DV75100048

    View details for PubMedID 2118274

  • CELL MOTILITY IS REQUIRED FOR THE TRANSMISSION OF C-FACTOR, AN INTERCELLULAR SIGNAL THAT COORDINATES FRUITING BODY MORPHOGENESIS OF MYXOCOCCUS-XANTHUS GENES & DEVELOPMENT Kim, S. K., Kaiser, D. 1990; 4 (6): 896-904

    Abstract

    There are striking similarities between the developmental phenotypes of two different mutant classes of Myxococcus xanthus. The first class, mglA mutants, are nonmotile under all conditions tested. The second class, csgA mutants, are motile but belong to a class of signal-defective developmental mutants that cannot develop alone but will develop when mixed with intact wild-type cells. Nevertheless, both csgA and mglA mutants fail to aggregate properly or to sporulate when induced to form fruiting bodies. An mglA mutation and a csgA mutation affect expression of a panel of lacZ fusions to developmental genes in the same way, indicating that nonmotile cells and csgA cells arrest development at a similar stage. One explanation for the similarity of developmental phenotypes between these mutants is that motility is required for the csgA-mediated cell interaction. In support of this hypothesis, we report that C-factor, a protein purified from nascent wild-type fruiting bodies based on its ability to rescue csgA mutant fruiting body development, also rescues sporulation and expression of beta-galactosidase from developmentally controlled lacZ fusions in mglA strains, apparently without restoring their motility. Wild-type levels of active C-factor can be purified from mglA cells, yet intact mglA cells do not rescue csgA cells upon cell-cell mixing. Intact wild-type cells are unable to restore the sporulation and beta-galactosidase expression of mglA mutants. These results support the hypothesis that donor and responder cell motility is required for C-factor transmission between cells during development.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for Web of Science ID A1990DJ09500002

    View details for PubMedID 2116988

  • PURIFICATION AND PROPERTIES OF MYXOCOCCUS-XANTHUS C-FACTOR, AN INTERCELLULAR SIGNALING PROTEIN PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Kim, S. K., Kaiser, D. 1990; 87 (10): 3635-3639

    Abstract

    C-factor, a Myxococcus xanthus protein that restores the developmental defects of a class of nonautonomous mutants resulting from mutation of the csgA gene, has been purified approximately 1000-fold from starved wild-type cells. The monomeric form of C-factor is a single polypeptide with a molecular mass of 17 kDa that can be solubilized by detergent from membrane components. Characterization by gel filtration and denaturing gel electrophoresis suggests that biologically active C-factor is a dimer composed of two 17-kDa monomers. Antibodies against a form of the M. xanthus csgA gene product overexpressed in Escherichia coli react with purified C-factor.

    View details for Web of Science ID A1990DD87300001

    View details for PubMedID 2111012

  • C-FACTOR - A CELL CELL SIGNALING PROTEIN REQUIRED FOR FRUITING BODY MORPHOGENESIS OF M-XANTHUS CELL Kim, S. K., Kaiser, D. 1990; 61 (1): 19-26

    Abstract

    During fruiting body development, the product of the csgA gene is necessary for cellular aggregation, for spore differentiation, and for gene expression that is initiated after 6 hr of starvation. From nascent wild-type fruiting bodies we have purified a polypeptide of 17 kd called C-factor, which, at approximately 1 to 2 nM, restores normal development to csgA mutant cells. C-factor activity is not recovered from extracts of unstarved, growing cells or csgA mutant cells. The amino acid sequence from purified C-factor demonstrates that it is the product of the csgA gene. C-factor is active over a narrow range of concentration and has properties of a morphogenetic paracrine signal.

    View details for Web of Science ID A1990CY38200006

    View details for PubMedID 2107980

  • PARA-DEPENDENT TRANSCRIPTION TERMINATION OF A BACTERIAL OPERON IS ANTAGONIZED BY AN EXTRACHROMOSOMAL GENE-PRODUCT PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Lagos, R., Jiang, R. Z., Kim, S., Goldstein, R. 1986; 83 (24): 9561-9565

    Abstract

    The psu gene product of "phasmid" (phage-plasmid) P4 acts as a transcription antitermination factor in trans and in cis, respectively, within the morphogenic operons of its P2 phage helper during lytic viral development and on P4 itself during the establishment stage of its alternative mode of propagation as a plasmid. Here we show that psu also antagonizes activity of the Escherichia coli transcription termination factor rho at the terminator of the trp operon. Such a finding provides to our knowledge the first direct evidence for antitermination activity at a known rho-dependent site by the psu gene product. It also reveals an example of an extrachromosomal gene product that acts on specific sites of three different genomes to regulate expression of unlinked families of genes.

    View details for Web of Science ID A1986F500600061

    View details for PubMedID 3540944

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