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Phosphorylation of NEUROG3 Links Endocrine Differentiation to the Cell Cycle in Pancreatic Progenitors.

ABSTRACT: During pancreatic development, proliferating pancreatic progenitors activate the proendocrine transcription factor neurogenin 3 (NEUROG3), exit the cell cycle, and differentiate into islet cells. The mechanisms that direct robust NEUROG3 expression within a subset of progenitor cells control the size of the endocrine population. Here we demonstrate that NEUROG3 is phosphorylated within the nucleus on serine 183, which catalyzes its hyperphosphorylation and proteosomal degradation. During progression through the progenitor cell cycle, NEUROG3 phosphorylation is driven by the actions of cyclin-dependent kinases 2 and 4/6 at G1/S cell-cycle checkpoint. Using models of mouse and human pancreas development, we show that lengthening of the G1 phase of the pancreatic progenitor cell cycle is essential for proper induction of NEUROG3 and initiation of endocrine cell differentiation. In sum, these studies demonstrate that progenitor cell-cycle G1 lengthening, through its actions on stabilization of NEUROG3, is an essential variable in normal endocrine cell genesis.

SUBMITTER: Krentz NAJ

PROVIDER: S-EPMC5517315 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature

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Phosphorylation of NEUROG3 Links Endocrine Differentiation to the Cell Cycle in Pancreatic Progenitors.

Krentz Nicole A J NAJ van Hoof Dennis D Li Zhongmei Z Watanabe Akie A Tang Mei M Nian Cuilan C German Michael S MS Lynn Francis C FC

Developmental cell 20170401 2

During pancreatic development, proliferating pancreatic progenitors activate the proendocrine transcription factor neurogenin 3 (NEUROG3), exit the cell cycle, and differentiate into islet cells. The mechanisms that direct robust NEUROG3 expression within a subset of progenitor cells control the size of the endocrine population. Here we demonstrate that NEUROG3 is phosphorylated within the nucleus on serine 183, which catalyzes its hyperphosphorylation and proteosomal degradation. During progres ...[more]

PMID: 28441528

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Project description:ObjectiveMice lacking the bHLH transcription factor (TF) Neurog3 do not form pancreatic islet cells, including insulin-secreting beta cells, the absence of which leads to diabetes. In humans, homozygous mutations of NEUROG3 manifest with neonatal or childhood diabetes. Despite this critical role in islet cell development, the precise function of and downstream genetic programs regulated directly by NEUROG3 remain elusive. Therefore, we mapped genome-wide NEUROG3 occupancy in human induced pluripotent stem cell (hiPSC)-derived endocrine progenitors and determined NEUROG3 dependency of associated genes to uncover direct targets.MethodsWe generated a novel hiPSC line (NEUROG3-HA-P2A-Venus) where NEUROG3 is HA-tagged and fused to a self-cleaving fluorescent VENUS reporter. We used the CUT&RUN technique to map NEUROG3 occupancy and epigenetic marks in pancreatic endocrine progenitors (PEP) that were differentiated from this hiPSC line. We integrated NEUROG3 occupancy data with chromatin status and gene expression in PEPs as well as their NEUROG3-dependence. In addition, we investigated whether NEUROG3 binds type 2 diabetes mellitus (T2DM)-associated variants at the PEP stage.ResultsCUT&RUN revealed a total of 863 NEUROG3 binding sites assigned to 1263 unique genes. NEUROG3 occupancy was found at promoters as well as at distant cis-regulatory elements that frequently overlapped within PEP active enhancers. De novo motif analyses defined a NEUROG3 consensus binding motif and suggested potential co-regulation of NEUROG3 target genes by FOXA or RFX transcription factors. We found that 22% of the genes downregulated in NEUROG3-/- PEPs, and 10% of genes enriched in NEUROG3-Venus positive endocrine cells were bound by NEUROG3 and thus likely to be directly regulated. NEUROG3 binds to 138 transcription factor genes, some with important roles in islet cell development or function, such as NEUROD1, PAX4, NKX2-2, SOX4, MLXIPL, LMX1B, RFX3, and NEUROG3 itself, and many others with unknown islet function. Unexpectedly, we uncovered that NEUROG3 targets genes critical for insulin secretion in beta cells (e.g., GCK, ABCC8/KCNJ11, CACNA1A, CHGA, SCG2, SLC30A8, and PCSK1). Thus, analysis of NEUROG3 occupancy suggests that the transient expression of NEUROG3 not only promotes islet destiny in uncommitted pancreatic progenitors, but could also initiate endocrine programs essential for beta cell function. Lastly, we identified eight T2DM risk SNPs within NEUROG3-bound regions.ConclusionMapping NEUROG3 genome occupancy in PEPs uncovered unexpectedly broad, direct control of the endocrine genes, raising novel hypotheses on how this master regulator controls islet and beta cell differentiation.

Dataset Information

Phosphorylation of NEUROG3 Links Endocrine Differentiation to the Cell Cycle in Pancreatic Progenitors.

Publications

Phosphorylation of NEUROG3 Links Endocrine Differentiation to the Cell Cycle in Pancreatic Progenitors.

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