1: Dev Biol. 2005 Mar 15;279(2):356-67. Sonic hedgehog and retinoic acid are not sufficient to induce motoneuron generation in the avian caudal neural tube. Afonso ND, Catala M. UMR CNRS 7000 and Laboratoire d'Histologie et Embryologie, Faculte de Medecine Pitie-Salpetriere, Universite Pierre et Marie Curie, 105, Bd. de l'Hopital, 75634 Paris Cedex 13, France. The caudal neural tube (CNT) of the avian embryo is devoid of both dorsal and ventral roots. We show that the lack of ventral roots in the CNT, from somite 48 caudalwards, is due to an absence of post-mitotic motoneurons (MNs). The absence of MNs is not due to a defective notochordal induction since Sonic Hedgehog (SHH) signaling is intact and the caudal notochord is able to induce ectopic MNs when grafted laterally to a host neural tube. The transcription factors involved in MN specification (Pax6, Nkx6.1, and Olig2) are all expressed in the CNT, despite the lower expression level of Pax6, but an overlap between Olig2 and the ventrally expressed transcription factor Nkx2.2 is observed in the CNT. Grafting a quail CNT into the cervical level of a chick host rescues MN generation, demonstrating both the CNT potential for MN generation and the key role of the caudal environment in the MN differentiation blockade. The transplantation of the CNT-flanking somites into the cervical level does not inhibit MN generation. Furthermore, implantation of a retinoic-acid-soaked bead laterally to the CNT does not rescue MN generation. Together, these data indicate that the rostral environment contains a signal different from both SHH and Retinoic Acid that acts on MN differentiation. PMID: 15733664 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 2: Pancreas. 2004 Oct;29(3):e64-76. Redox-mediated enrichment of self-renewing adult human pancreatic cells that possess endocrine differentiation potential. Linning KD, Tai MH, Madhukar BV, Chang CC, Reed DN Jr, Ferber S, Trosko JE, Olson LK. Department of Physiology, Michigan State University, East Lansing, Michigan 48824, USA. OBJECTIVES: The limited availability of transplantable human islets has stimulated the development of methods needed to isolate adult pancreatic stem/progenitor cells capable of self-renewal and endocrine differentiation. The objective of this study was to determine whether modulation of intracellular redox state with N-acetyl-L-cysteine (NAC) would allow for the propagation of pancreatic stem/progenitor cells from adult human pancreatic tissue. METHODS: Cells were propagated from human pancreatic tissue using a serum-free, low-calcium medium supplemented with NAC and tested for their ability to differentiate when cultured under different growth conditions. RESULTS: Human pancreatic cell (HPC) cultures coexpressed alpha-amylase, albumin, vimentin, and nestin. The HPC cultures, however, did not express other genes associated with differentiated pancreatic exocrine, duct, or endocrine cells. A number of transcription factors involved in endocrine cell development including Beta 2, Islet-1, Nkx6.1, Pax4, and Pax6 were expressed at variable levels in HPC cultures. In contrast, pancreatic duodenal homeobox factor 1 (Pdx-1) expression was extremely low and at times undetectable. Overexpression of Pdx-1 in HPC cultures stimulated somatostatin, glucagon, and carbonic anhydrase expression but had no effect on insulin gene expression. HPC cultures could form 3-dimensional islet-like cell aggregates, and this was associated with expression of somatostatin and glucagon but not insulin. Cultivation of HPCs in a differentiation medium supplemented with nicotinamide, exendin-4, and/or LY294002, an inhibitor of phosphatidylinositol-3 kinase, stimulated expression of insulin mRNA and protein. CONCLUSION: These data support the use of intracellular redox modulation for the enrichment of pancreatic stem/progenitor cells capable of self-renewal and endocrine differentiation. PMID: 15367896 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 3: Diabetes. 2004 Sep;53(9):2322-9. Dissecting the role of glucocorticoids on pancreas development. Gesina E, Tronche F, Herrera P, Duchene B, Tales W, Czernichow P, Breant B. INSERM U457, Hopital Robert Debre, Paris F 75019, France. To determine whether glucocorticoids are involved in pancreas development, glucocorticoid treatment of rat pancreatic buds in vitro was combined with the analysis of transgenic mice lacking the glucocorticoid receptor (GR) in specific pancreatic cells. In vitro treatment of embryonic pancreata with dexamethasone, a glucocorticoid agonist, induced a decrease of insulin-expressing cell numbers and a doubling of acinar cell area, indicating that glucocorticoids favored acinar differentiation; in line with this, expression of Pdx-1, Pax-6, and Nkx6.1 was downregulated, whereas the mRNA levels of Ptf1-p48 and Hes-1 were increased. The selective inactivation of the GR gene in insulin-expressing beta-cells in mice (using a RIP-Cre transgene) had no measurable consequences on beta- or alpha-cell mass, whereas the absence of GR in the expression domain of Pdx-1 (Pdx-Cre transgene) led to a twofold increased beta-cell mass, with increased islet numbers and size but normal alpha-cell mass in adults. These results demonstrate that glucocorticoids play an important role in pancreatic beta-cell lineage, acting before hormone gene expression onset and possibly also modulating the balance between endocrine and exocrine cell differentiation. PMID: 15331541 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 4: J Comp Neurol. 2003 Feb 10;456(3):237-44. Molecular mapping of the origin of postnatal spinal cord ependymal cells: evidence that adult ependymal cells are derived from Nkx6.1+ ventral neural progenitor cells. Fu H, Qi Y, Tan M, Cai J, Hu X, Liu Z, Jensen J, Qiu M. Department of Anatomical Sciences and Neurobiology, School of Medicine, University of Louisville, Kentucky 40292, USA. Recent studies have suggested that the ependymal cells lining the central canal of postnatal spinal cord possess certain properties of neural stem cells. However, the embryonic origin and developmental potential of the postnatal spinal cord ependymal cells remain to be defined. In this report, we investigated the developmental origin of postnatal spinal ependymal cells by studying the dynamic expression of several neural progenitor genes that are initially expressed in distinct domains of neuroepithelium in young embryos. At later stages of development, as the ventricular zone of the embryonic spinal cord is reduced, expression of Nkx6.1 progenitor gene is constantly detected in ependymal cells throughout chick and mouse development. Expression of other neural progenitor genes that lie either dorsal or ventral to the Nkx6.1+ domain is gradually decreased and eventually disappeared. These results suggest that the remaining neuroepithelial cells at later stages of animal life are derived from the Nkx6.1+ ventral neuroepithelial cells. Expression of Nkx6.1 in the remaining neuroepithelium is closely associated with, and regulated by, Shh expression in the floor plate. In addition, we suggested that the Nkx6.1+ ependymal cells in adult mouse spinal cords may retain the proliferative property of neural stem cells. Copyright 2003 Wiley-Liss, Inc. PMID: 12528188 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 5: Pancreas. 2003 Jan;26(1):71-5. Analysis of gene expression and insulin secretion by monolayer-forming adult porcine pancreatic endocrine cells. Tsuchiya M, Tsuchiya K, Iwami Y, Ohgawara H. Institute of Geriatrics, Aoyama Hospital, Medical Research Institute, Tokyo Women's Medical University, Tokyo, Japan. INTRODUCTION: We recently established a method of isolation and primary monolayer culture of porcine pancreatic endocrine cells that involves the use of nicotinamide. AIM: To obtain genetic information on cultured porcine endocrine cells and to examine cell function in relation to insulin secretion during long-term culture. METHODOLOGY: Gene expression of insulin and several transcription factors, including PDX-1, Beta2/NeuroD, Pax6, and Nkx6.1, was assessed by reverse transcription-polymerase chain reaction analysis, and the insulin protein level was estimated by immunohistochemistry and enzyme assay during a 12-week period. RESULTS: During the culture period, insulin accumulation in the medium at 5 weeks had decreased by almost half the level of accumulation in the first week. In contrast to the alteration of secretory function, insulin gene expression was maintained for at least 12 weeks, and regulatory transcription factors were expressed at the same levels until 9 weeks. These observations suggest that gene expression is not involved in the cause of decreased baseline insulin secretion. Moreover, although the insulin response to high glucose and potassium loading was maintained, the magnitude of the responses to both stimuli was attenuated in the late period of culture. Insulin secretion tended to decrease in our culture system, and the secretory response to pharmacological stimulation was attenuated despite maintenance of messenger RNA expression of insulin and other islet-specific genes for at least 9 weeks in vitro. CONCLUSION: These findings indicate that cell integrity is maintained and that the alteration in insulin secretion must be explained by another mechanism. PMID: 12499920 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 6: J Autoimmun. 2002 Dec;19(4):203-13. Low expression of insulin in the thymus of non-obese diabetic mice. Brimnes MK, Jensen T, Jorgensen TN, Michelsen BK, Troelsen J, Werdelin O. Institute for Medical Microbiology and Immunology, University of Copenhagen, Copenhagen, Denmark. marie.brimnes@mssm.edu Insulin is a predominant autoantigen in IDDM in man and the NOD mouse. Failure of negative selection of diabetogenic T cells in thymus may be an important pre-disposing cause of the disease. To obtain insight into negative selection against such T-cell clones the thymic expression of insulin was studied in NOD and Balb/c mice by quantitative competitive RT-PCR. We detected RNA for insulin in the thymus of 3-week-old Balb/c mice as well as in NOD mice. However, the NOD mice expressed only half as many insulin transcripts as the Balb/c mice. Also, insulin protein was detected in the thymic medulla of both Balb/c and NOD mice. Furthermore, thymic RNA preparations were investigated for the presence of insulin transcription factors. None of the known pancreatic transcription factors for insulin; Pdx-1, Pax6 or Nkx6.1 were detectable in the thymus of Balb/c mice. These results support the idea that low insulin expression in the thymus may be a predisposing cause for development of diabetes in NOD mice analogous with what has been found in humans with the disease-disposing IDDM2 allele. Furthermore, our results suggest that insulin expression in the thymus may be regulated by different principles from those in the pancreas. PMID: 12473241 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 7: J Cell Biol. 2002 Oct 28;159(2):303-12. Epub 2002 Oct 28. Recapitulation of embryonic neuroendocrine differentiation in adult human pancreatic duct cells expressing neurogenin 3. Heremans Y, Van De Casteele M, in't Veld P, Gradwohl G, Serup P, Madsen O, Pipeleers D, Heimberg H. Diabetes Research Center, Brussels Free University (VUB), Laarbeeklaan 103, B-1090 Brussels, Belgium. Regulatory proteins have been identified in embryonic development of the endocrine pancreas. It is unknown whether these factors can also play a role in the formation of pancreatic endocrine cells from postnatal nonendocrine cells. The present study demonstrates that adult human pancreatic duct cells can be converted into insulin-expressing cells after ectopic, adenovirus-mediated expression of the class B basic helix-loop-helix factor neurogenin 3 (ngn3), which is a critical factor in embryogenesis of the mouse endocrine pancreas. Infection with adenovirus ngn3 (Adngn3) induced gene and/or protein expression of NeuroD/beta2, Pax4, Nkx2.2, Pax6, and Nkx6.1, all known to be essential for beta-cell differentiation in mouse embryos. Expression of ngn3 in adult human duct cells induced Notch ligands Dll1 and Dll4 and neuroendocrine- and beta-cell-specific markers: it increased the percentage of synaptophysin- and insulin-positive cells 15-fold in ngn3-infected versus control cells. Infection with NeuroD/beta2 (a downstream target of ngn3) induced similar effects. These data indicate that the Delta-Notch pathway, which controls embryonic development of the mouse endocrine pancreas, can also operate in adult human duct cells driving them to a neuroendocrine phenotype with the formation of insulin-expressing cells. PMID: 12403815 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 8: Development. 2002 Nov;129(22):5241-53. The role of Phox2b in synchronizing pan-neuronal and type-specific aspects of neurogenesis. Dubreuil V, Hirsch MR, Jouve C, Brunet JF, Goridis C. CNRS UMR 8542, Departement de Biologie, Ecole Normale Superieure, 46, rue d'Ulm, 75230 Paris Cedex 05, France. Within the developing vertebrate nervous system, specific subclasses of neurons are produced in vastly different numbers at defined times and locations. This implies the concomitant activation of a program that controls pan-neuronal differentiation and of a program that specifies neuronal subtype identity, but how these programs are coordinated in time and space is not well understood. Our previous loss- and gain-of-function studies have defined Phox2b as a homeodomain transcription factor that coordinately regulates generic and type-specific neuronal properties. It is necessary and sufficient to impose differentiation towards a branchio- and viscero-motoneuronal phenotype and at the same time promotes generic neuronal differentiation. We have examined the underlying genetic interactions. We show that Phox2b has a dual action on pan-neuronal differentiation. It upregulates the expression of proneural genes (Ngn2) when expressed alone and upregulates the expression of Mash1 when expressed in combination with Nkx2.2. By a separate pathway, Phox2b represses expression of the inhibitors of neurogenesis Hes5 and Id2. The role of Phox2b in the specification of neuronal subtype identity appears to depend in part on its capacity to act as a patterning gene in the progenitor domain. Phox2b misexpression represses the Pax6 and Olig2 genes, which should inhibit a branchiomotor fate, and induces Nkx6.1 and Nkx6.2, which are expressed in branchiomotor progenitors. We further show that Phox2b behaves like a transcriptional activator in the promotion of both, generic neuronal differentiation and expression of the motoneuronal marker Islet1. These results provide insights into the mechanisms by which a homeodomain transcription factor through interaction with other factors controls both generic and type-specific features of neuronal differentiation. PMID: 12399315 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 9: Development. 2002 Mar;129(6):1327-38. Pax6 regulates specification of ventral neurone subtypes in the hindbrain by establishing progenitor domains. Takahashi M, Osumi N. Department of Developmental Neurobiology, Tohoku University Graduate School of Medicine, 2-1, Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan. Recent studies have shown that generation of different kinds of neurones is controlled by combinatorial actions of homeodomain (HD) proteins expressed in the neuronal progenitors. Pax6 is a HD protein that has previously been shown to be involved in the differentiation of the hindbrain somatic (SM) motoneurones and V1 interneurones in the hindbrain and/or spinal cord. To investigate in greater depth the role of Pax6 in generation of the ventral neurones, we first examined the expression patterns of HD protein genes and subtype-specific neuronal markers in the hindbrain of the Pax6 homozygous mutant rat. We found that Islet2 (SM neurone marker) and En1 (V1 interneurone marker) were transiently expressed in a small number of cells, indicating that Pax6 is not directly required for specification of these neurones. We also observed that domains of all other HD protein genes (Nkx2.2, Nkx6.1, Irx3, Dbx2 and Dbx1) were shifted and their boundaries became blurred. Thus, Pax6 is required for establishment of the progenitor domains of the ventral neurones. Next, we performed Pax6 overexpression experiments by electroporating rat embryos in whole embryo culture. Pax6 overexpression in the wild type decreased expression of Nkx2.2, but ectopically increased expression of Irx3, Dbx1 and Dbx2. Moreover, electroporation of Pax6 into the Pax6 mutant hindbrain rescued the development of Islet2-positive and En1-positive neurones. To know reasons for perturbed progenitor domain formation in Pax6 mutant, we examined expression patterns of Shh signalling molecules and states of cell death and cell proliferation. Shh was similarly expressed in the floor plate of the mutant hindbrain, while the expressions of Ptc1, Gli1 and Gli2 were altered only in the progenitor domains for the motoneurones. The position and number of TUNEL-positive cells were unchanged in the Pax6 mutant. Although the proportion of cells that were BrdU-positive slightly increased in the mutant, there was no relationship with specific progenitor domains. Taken together, we conclude that Pax6 regulates specification of the ventral neurone subtypes by establishing the correct progenitor domains. PMID: 11880342 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 10: Neuron. 2001 Sep 13;31(5):743-55. Different levels of repressor activity assign redundant and specific roles to Nkx6 genes in motor neuron and interneuron specification. Vallstedt A, Muhr J, Pattyn A, Pierani A, Mendelsohn M, Sander M, Jessell TM, Ericson J. Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institute, S-171 77, Stockholm, Sweden. Specification of neuronal fate in the vertebrate central nervous system depends on the profile of transcription factor expression by neural progenitor cells, but the precise roles of such factors in neurogenesis remain poorly characterized. Two closely related transcriptional repressors, Nkx6.2 and Nkx6.1, are expressed by progenitors in overlapping domains of the ventral spinal cord. We provide genetic evidence that differences in the level of repressor activity of these homeodomain proteins underlies the diversification of interneuron subtypes, and provides a fail-safe mechanism during motor neuron generation. A reduction in Nkx6 activity further permits V0 neurons to be generated from progenitors that lack homeodomain proteins normally required for their generation, providing direct evidence for a model in which progenitor homeodomain proteins direct specific cell fates by actively suppressing the expression of transcription factors that direct alternative fates. PMID: 11567614 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 11: Mol Cell Endocrinol. 2000 Jul 25;165(1-2):41-9. Transcription factor expression and hormone production in pancreatic AR42J cells. Palgi J, Stumpf E, Otonkoski T. Transplantation Laboratory, Haartman Institute and the Hospital for Children and Adolescents, University of Helsinki, PO Box 21 (Haartmaninkatu 3), FIN-00014, Helsinki, Finland. jaan.palgi@helsinki.fi AR42J is an exocrine pancreatic cell line that has been reported to differentiate towards an endocrine phenotype when stimulated with various growth factors, such as activin A, hepatocyte growth factor (HGF), betacellulin or glucagon-like peptide 1. In our experiments, AR42J-B13 cells differentiated morphologically in response to the growth factor treatment as reported previously. However, they failed to express the insulin gene. We found that the cells did not express several transcription factors known to be found in the beta-cell, including Nkx6.1, isl-1, Pax4 and Pax6. In addition, the mRNA level for pdx-1 and Nkx2.2 were very low in comparison to the insulinoma cell lines INS-1 and RINm5F. However, some transcription factors typically found in beta-cells and neuroendocrine cells were expressed also in the AR42J-B13 cells. These included BETA2/NeuroD, HNF1alpha, C/EBPbeta and IA-1. Unlike the insulinoma cells, AR42J cells expressed the exocrine transcription factor p48. In order to induce endocrine differentiation, we transfected the AR42J-B13 cells with the full length cDNAs of isl-1, Nkx6.1, Nkx2.2 and pdx-1 under the control of the CMV promoter, both separately and in combinations. The expression of Nkx2.2 led consistently to the appearance of pancreatic polypeptide but not insulin, glucagon or somatostatin mRNA. The PP mRNA expression in Nkx2.2 cDNA transfected cells was independent of the growth factor treatment used for differentiating AR42J cells. In conclusion, the AR42J-B13 line possesses some features of a pancreatic neuroendocrine cell. However, we were unable to confirm the capacity of these cells to differentiate into insulin-producing cells. Our results indicate that Nkx2.2 plays a role in the transcriptional regulation of PP expression. PMID: 10940482 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 12: Development. 2000 Aug;127(16):3533-42. Expression of neurogenin3 reveals an islet cell precursor population in the pancreas. Schwitzgebel VM, Scheel DW, Conners JR, Kalamaras J, Lee JE, Anderson DJ, Sussel L, Johnson JD, German MS. Hormone Research Institute, Department of Pediatrics, and Department of Medicine, University of California San Francisco, San Francisco, CA 94143, USA. Differentiation of early gut endoderm cells into the endocrine cells forming the pancreatic islets of Langerhans depends on a cascade of gene activation events controlled by transcription factors including the basic helix-loop-helix (bHLH) proteins. To delineate this cascade, we began by establishing the position of neurogenin3, a bHLH factor found in the pancreas during fetal development. We detect neurogenin3 immunoreactivity transiently in scattered ductal cells in the fetal mouse pancreas, peaking at embryonic day 15.5. Although not detected in cells expressing islet hormones or the islet transcription factors Isl1, Brn4, Pax6 or PDX1, neurogenin3 is detected along with early islet differentiation factors Nkx6.1 and Nkx2.2, establishing that it is expressed in immature cells in the islet lineage. Analysis of transcription factor-deficient mice demonstrates that neurogenin3 expression is not dependent on neuroD1/BETA2, Mash1, Nkx2.2, Nkx6.1, or Pax6. Furthermore, early expression of neurogenin3 under control of the Pdx1 promoter is alone sufficient to drive early and ectopic differentiation of islet cells, a capability shared by the pancreatic bHLH factor, neuroD1/BETA2, but not by the muscle bHLH factor, MyoD. However, the islet cells produced in these transgenic experiments are overwhelmingly (alpha) cells, suggesting that factors other than the bHLH factors are required to deviate from a default * cell fate. These data support a model in which neurogenin3 acts upstream of other islet differentiation factors, initiating the differentiation of endocrine cells, but switching off prior to final differentiation. The ability to uniquely identify islet cell precursors by neurogenin3 expression allows us to determine the position of other islet transcription factors in the differentiation cascade and to propose a map for the islet cell differentiation pathway. PMID: 10903178 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 13: Pancreas. 2000 May;20(4):337-47. Differentiation of islet cells in long-term culture. Schmied BM, Liu G, Matsuzaki H, Ulrich A, Hernberg S, Moyer MP, Weide L, Murphy L, Batra SK, Pour PM. UNMC Eppley Cancer Center, University of Nebraska Medical Center, Omaha 68198-6805, USA. Our previous studies in the hamster pancreatic cancer model have shown that exocrine pancreatic cancer arises from ductal/ductular cells, as well as from within the islets, most probably from islet precursor (stem) cells. To identify and characterize these cells, we established a long-term culture from isolated hamster islets and investigated their growth, differentiation, and expression of biomarkers. Islets maintained their original form and structure within the first 14 days in culture. However, beginning at day 7, ductular structures began to form within the islets. At day 21 in culture, acinar cells, intermediary cells, oncocytes, and cells comparable to pancreatic hepatocytes also appeared between ductular and endocrine cells. The number of duct-like cells gradually increased, whereas the number of hormone-producing cells decreased. After 35 days in culture, the exocrine cells disappeared, and undifferentiated cells formed a monolayer. These cells expressed cytokeratins, alpha1-antitrypsin, transforming growth factor-alpha, epidermal growth factor receptor, carbonic anhydrase II, vimentin, laminin, and showed binding to tomato lectin and Phaseolus vulgaris leukoagglutinin. They did not express the regulatory transcriptional factors, insulin-promoting factor 1, NKx6.1, Pax6, and NeuroD. The results thus indicate that islet cells have potential to form exocrine cells. At present, it is not clear whether these cells originate from preexisting stem cells or from transdifferentiated islet cells. PMID: 10824687 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 14: FEBS Lett. 1999 Nov 19;461(3):287-94. Cloning and DNA-binding properties of the rat pancreatic beta-cell-specific factor Nkx6.1. Jorgensen MC, Vestergard Petersen H, Ericson J, Madsen OD, Serup P. Department of Developmental Biology, Hagedorn Research Institute, Niels Steensensvej 6, DK-2820, Gentofte, Denmark. The homeodomain (HD) protein Nkx6.1 is the most beta-cell-specific transcription factor known in the pancreas and its function is critical for the formation of the insulin-producing beta-cells. However, the target genes, DNA-binding site, and transcriptional properties of Nkx6.1 are unknown. Using in vitro binding site selection we have identified the DNA sequence of the Nkx6.1 binding site to be TTAATTG/A. A reporter plasmid containing four copies of this sequence is activated by an Nkx6.1HD/VP16 fusion construct. Full-length Nkx6.1 fails to activate this reporter plasmid in spite of robust interaction with the binding site in vitro. Stable expression of Nkx6.1 in the glucagon-producing alpha-cell-like MSL-G-AN cells induces expression of the endogenous insulin gene in a subset of the cell population. The expression of other known beta-cell-specific factors such as Pax4, Pax6, Pdx1, GLUT2 and GLP1-R is unchanged by the introduction of Nkx6.1. PMID: 10567713 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 15: Int J Mol Med. 1999 Mar;3(3):247-61. Development of pancreatic islets (review). Yamaoka T, Itakura M. Otsuka Department of Clinical and Molecular Nutrition, School of Medicine, The University of Tokushima, Tokushima 770-8503, Japan. Recent studies have revealed that islet cells differentiate from the epithelial cells of primitive pancreatic ducts during embryogenesis, and can regenerate in response to the loss of islet cells even in adult pancreas. The ability of islet cells to regenerate raises the possibility that impaired and decreased islets of diabetic patients can be restored. In this review, factors regulating islet development including differentiation factors (Shh, activin, follistatin, and TGF alpha), transcriptional factors (PDX1, Isl1, Pax4, Pax6, Nkx2.2, Nkx6.1, BETA2, and HNF), growth factors (the EGF family, HGF, IGF-I, IGF-II, Reg, INGAP, PDGF, FGF, VEGF, and NGF), hormones (insulin, the GH family, PTHrP, TRH, and gastrin), and cell adhesion molecules (N-CAM and cadherins) are described after a short introduction and an outline of pancreatic development. Publication Types: Review Review, Tutorial PMID: 10028048 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 16: Proc Natl Acad Sci U S A. 1998 Jul 21;95(15):8654-9. Targeted oncogenesis of hormone-negative pancreatic islet progenitor cells. Jetton TL, Moates JM, Lindner J, Wright CV, Magnuson MA. Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-0615, USA. Transgenic mice containing an upstream glucokinase (betaGK) promoter- simian virus 40 T antigen (Tag) fusion gene develop neuroendocrine tumors primarily in the pancreas, gut, and pituitary. Pancreatic tumors from a line with delayed tumorigenesis were of two different types: insulinomas and noninsulinomas. The noninsulinomas are often periductal in location, express none of the four major islet peptide hormones, Glut-2, Pdx1, tyrosine hydroxylase, Pax4, Pax6, or Nkx6.1, but do express glucokinase, Sur1, Isl1, Hnf3beta, Hnf6, Beta2/NeuroD, and Nkx2.2. Cells from two different noninsulinoma tumors, when adapted to culture, began to express either insulin, glucagon, or somatostatin. Given the partial gene expression repertoire of the noninsulinoma tumors, their apparent periductal origin, and the ability of these cells to partially cytodifferentiate in culture, we suggest that these tumors are derived from islet progenitor cells. Thus, betaGK-Tag transgenic mice provide a new model system for studying the events that occur during both islet cell neogenesis and normal embryonic development. PMID: 9671733 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 17: Development. 1998 Jun;125(12):2213-21. Mice lacking the homeodomain transcription factor Nkx2.2 have diabetes due to arrested differentiation of pancreatic beta cells. Sussel L, Kalamaras J, Hartigan-O'Connor DJ, Meneses JJ, Pedersen RA, Rubenstein JL, German MS. Nina Ireland Laboratory of Developmental Neurobiology, Department of Psychiatry, University of California, San Francisco, CA 94143, USA. The endocrine pancreas is organized into clusters of cells called islets of Langerhans comprising four well-defined cell types: alpha beta, delta and PP cells. While recent genetic studies indicate that islet development depends on the function of an integrated network of transcription factors, the specific roles of these factors in early cell-type specification and differentiation remain elusive. Nkx2.2 is a member of the mammalian NK2 homeobox transcription factor family that is expressed in the ventral CNS and the pancreas. Within the pancreas, we demonstrate that Nkx2.2 is expressed in alpha, beta and PP cells, but not in delta cells. In addition, we show that mice homozygous for a null mutation of Nkx2.2 develop severe hyperglycemia and die shortly after birth. Immunohistochemical analysis reveals that the mutant embryos lack insulin-producing beta cells and have fewer glucagon-producing alpha cells and PP cells. Remarkably, in the mutants there remains a large population of islet cells that do not produce any of the four endocrine hormones. These cells express some beta cell markers, such as islet amyloid polypeptide and Pdx1, but lack other definitive beta cell markers including glucose transporter 2 and Nkx6.1. We propose that Nkx2.2 is required for the final differentiation of pancreatic beta cells, and in its absence, beta cells are trapped in an incompletely differentiated state. PMID: 9584121 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 18: Horm Metab Res. 1997 Jun;29(6):265-70. Transcription factors contributing to the pancreatic beta-cell phenotype. Madsen OD, Jensen J, Petersen HV, Pedersen EE, Oster A, Andersen FG, Jorgensen MC, Jensen PB, Larsson LI, Serup P. Department of Developmental Biology, Hagedorn Research Institute, Gentofte, Denmark. Insulin promoter factor-1 (IPF1) (renamed to pancreatic-duodenal homeobox factor-1, PDX1) was originally cloned and characterized as an islet beta-cell specific insulin gene transcription factor (1) and later shown to be essential for the formation of the mature pancreas (2, 3). In the adult normal pancreas PDX1 is almost exclusively expressed in the beta-cell compartment and generally absent from the alpha-cell while it is widely expressed in the pancreatic epithelium during development. Using pluripotent rat islet tumor cultures and derived insulinomas and glucagonomas we have analyzed differential expression of a large number of genes including the transcription factors PDX1, Nkx6.1, Pax6, and NeuroD. While NeuroD and Pax6 expression was detectable among all phenotypes, PDX1 was expressed in the pluripotent culture and maintained in the insulinoma, while Nkx6.1 was selectively co-induced with insulin during insulinoma formation. Both factors were not detectable in the glucagonoma. Nkx6.1 proved to have a highly beta-cell restricted expression in the adult rat. Forced expression of recombinant PDX1 in the glucagonoma resulted in efficient transcriptional activation of the endogenous insulin and IAPP genes, but did not affect glucagon gene activity. In this hybrid alpha/beta-cell phenotype the endogenous Nkx6.1 gene remained silent. We conclude that PDX1 in synergy with NeuroD specifies part of the beta-cell phenotype including transcriptional activation of insulin and IAPP genes, but that other factors such as Nkx6.1 and Pax6 are required for additional features of the fully mature beta-cell phenotype. Publication Types: Review Review, Tutorial PMID: 9230347 [PubMed - indexed for MEDLINE] ---------------------------------------------------------------