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Jensen, J. et al. Independent development of pancreatic alpha- and beta-cells from neurogenin3-expressing precursors: a role for the notch pathway in repression of premature differentiation. Diabetes 49, 163-176

Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Ángeles, California, United States
Diabetes (Impact Factor: 8.47). 03/2000; 49(2):163-76. DOI: 10.2337/diabetes.49.2.163
Source: PubMed

ABSTRACT The nature and identity of the pancreatic beta-cell precursor has remained elusive for many years. One model envisions an early multihormonal precursor that gives rise to both alpha- and beta-cells and the other endocrine cell types. Alternatively, beta-cells have been suggested to arise late, directly from the GLUT2- and pancreatic duodenal homeobox factor-1 (PDX1)-expressing epithelium, which gives rise also to the acinar cells during this stage. In this study, we have identified a subset of the PDX1+ epithelial cells that are marked by expression of Neurogenin3 (Ngn3). Ngn3, a member of the basic helix-loop-helix (bHLH) family of transcription factors, is suggested to act upstream of NeuroD in a bHLH cascade. Detailed analysis of Ngn3/paired box factor 6 (PAX6) and NeuroD/PAX6 co-expression shows that the two bHLH factors are expressed in a largely nonoverlapping set of cells, but such analysis also suggests that the NeuroD+ cells arise from cells expressing Ngn3 transiently. NeuroD+ cells do not express Ki-67, a marker of proliferating cells, which shows that these cells are postmitotic. In contrast, Ki-67 is readily detected in Ngn3+ cells. Thus, Ngn3+ cells fulfill the criteria for an endocrine precursor cell. These expression patterns support the notion that both alpha- and beta-cells develop independently from PDX1+/Ngn3+ epithelial cells, rather than from GLU+/INS+ intermediate stages. The earliest sign of alpha-cell development appears to be Brain4 expression, which apparently precedes Islet-1 (ISL1) expression. Based on our expression analysis, we propose a temporal sequence of gene activation and inactivation for developing alpha- and beta-cells beginning with activation of NeuroD expression. Endocrine cells leave the cell cycle before NeuroD activation, but re-enter the cell cycle at perinatal stages. Dynamic expression of Notch1 in PDX+ epithelial cells suggests that Notch signaling could inhibit a Ngn-NeuroD cascade as seen in the nervous system and thus prevent premature differentiation of endocrine cells.

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    • "Several different signaling pathways are essential for pancreas development (Kimmel and Meyer, 2010; Serup, 2012). For instance, Notch signaling has long been known as central to both mammalian (Apelqvist et al., 1999; Esni et al., 2004; Hald et al., 2003; Jensen et al., 2000; Murtaugh et al., 2003) and zebrafish pancreas development (Esni et al., 2004; Lorent et al., 2004; Ninov et al., 2012; Parsons et al., 2009; Zecchin et al., 2007). Inhibition of Notch signaling leads to precocious differentiation of PNCs and the early appearance of endocrine cell types in the 21 islet position within the pancreatic tail (Parsons et al., 2009). "
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    ABSTRACT: As the developing zebrafish pancreas matures, hormone-producing endocrine cells differentiate from pancreatic Notch-responsive cells (PNCs) that reside within the ducts. These new endocrine cells form small clusters known as secondary (2°) islets. We use the formation of 2° islets in the pancreatic tail of the larval zebrafish as a model of β-cell neogenesis. Pharmacological inhibition of Notch signaling leads to precocious endocrine differentiation and the early appearance of 2° islets in the tail of the pancreas. Following a chemical screen, we discovered that blocking the retinoic acid (RA)-signaling pathway also leads to the induction of 2° islets. Conversely, the addition of exogenous RA blocks the differentiation caused by Notch inhibition. In this report we characterize the interaction of these two pathways. We first verified that signaling via both RA and Notch ligands act together to regulate pancreatic progenitor differentiation. We produced a transgenic RA reporter, which demonstrated that PNCs directly respond to RA signaling through the canonical transcriptional pathway. Next, using a genetic lineage tracing approach, we demonstrated these progenitors produce endocrine cells following inhibition of RA signaling. Lastly, inhibition of RA signaling using a cell-type specific inducible cre/lox system revealed that RA signaling acts cell-autonomously in PNCs to regulate their differentiation. Importantly, the action of RA inhibition on endocrine formation is evolutionarily conserved, as shown by the differentiation of human embryonic stem cells in a model of human pancreas development. Together, these results revealed a biphasic function for RA in pancreatogenesis. As previously shown by others, RA initially plays an essential role during embryogenesis as it patterns the endoderm and specifies the pancreatic field. We reveal here that later in development RA is involved in negatively regulating the further differentiation of pancreatic progenitors and expands upon the developmental mechanisms by which this occurs.
    Developmental Biology 08/2014; DOI:10.1016/j.ydbio.2014.07.021 · 3.64 Impact Factor
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    • "The NOTCH pathway components are not normally expressed in adult terminally differentiated murine pancreatic cells (Esni et al., 2004; Jensen, Pedersen, et al., 2000). Unlike in pancreatic progenitor cells, NICD overexpression (Murtaugh et al., 2003) or Rbp-jk inactivation (Fujikura et al., 2006) in fully differentiated b cells does not cause an obvious phenotype . "
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    ABSTRACT: Beta-cell replacement represents the optimal therapy for type 1 diabetes. Efforts to manipulate β-cell proliferation and differentiation could be advanced by a better understanding of the normal pathways regulating β-cell development and renewal. NOTCH signaling is a highly conserved pathway which plays a central role in pancreas development. Cell-lineage tracing has revealed the reactivation of the NOTCH pathway in adult human β cells cultured under conditions which induce cell proliferation and dedifferentiation. Inhibition of NOTCH signaling in dedifferentiated cells following ex vivo expansion has been shown to promote restoration of the β-cell phenotype. This approach may increase the availability of functional β cells for transplantation.
    Vitamins & Hormones 01/2014; 95:391-405. DOI:10.1016/B978-0-12-800174-5.00015-6 · 1.78 Impact Factor
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    • "The mechanism of increasing the size of the islands is the subject of many studies. Several kinetic studies have presented that there are two waves of differentiation of endocrine cells in the development of the pancreas of mice (Herrera PL, 2000; Jensen J. et al., 2000). The first wave -that are cells that appear on the early stages of development (from 9.5 ED) and co-expressing several hormones. "
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    Pancreas: Anatomy, Diseases and Health Implications, 1 edited by Akiko Satou, Hana Nakamura, 09/2012: chapter 2: pages 53-87; Nova Science Publisher., ISBN: 978-1-62081-539-7
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