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Objectives Insulin receptor (IR)-mediated signaling is involved in the regulation of pluripotent stem cells; however, its direct effects on regulating the maintenance of pluripotency and lineage development are not fully understood. The main objective of this study is to understand the role of IR signaling in pluripotency and lineage development. Methods To explore the role of IR signaling, we generated IR knock-out (IRKO) mouse induced pluripotent stem cells (miPSCs) from E14.5 mouse embryonic fibroblasts (MEFs) of global IRKO mice using a cocktail of four reprogramming factors: Oct4, Sox2, Klf4, cMyc. We performed pluripotency characterization and directed the differentiation of control and IRKO iPSCs into neural progenitors (ectoderm), adipocyte progenitors (mesoderm), and pancreatic beta-like cells (endoderm). We mechanistically confirmed these findings via phosphoproteomics analyses of control and IRKO iPSCs. Results Interestingly, expression of pluripotency markers including Klf4, Lin28a, Tbx3, and cMyc were upregulated, while abundance of Oct4 and Nanog were enhanced by 4-fold and 3-fold, respectively, in IRKO iPSCs. Analyses of signaling pathways demonstrated downregulation of phospho-STAT3, p-mTor and p-Erk and an increase in the total mTor and Erk proteins in IRKO iPSCs in the basal unstimulated state. Stimulation with leukemia inhibitory factor (LIF) showed a ∼33% decrease of phospho-ERK in IRKO iPSCs. On the contrary, Erk phosphorylation was increased during in vitro spontaneous differentiation of iPSCs lacking IRs. Lineage-specific directed differentiation of the iPSCs revealed that cells lacking IR showed enhanced expression of neuronal lineage markers (Pax6, Tubb3, Ascl1 and Oligo2) while exhibiting a decrease in adipocyte (Fas, Acc, Pparγ, Fabp4, C/ebpα, and Fsp27) and pancreatic beta cell markers (Ngn3, Isl1, and Sox9). Further molecular characterization by phosphoproteomics confirmed the novel IR-mediated regulation of the global pluripotency network including several key proteins involved in diverse aspects of growth and embryonic development. Conclusion We report, for the first time to our knowledge, the phosphoproteome of insulin, IGF1, and LIF stimulation in mouse iPSCs to reveal the importance of insulin receptor signaling for the maintenance of pluripotency and lineage determination., Graphical abstract Image 1, Highlights • Insulin receptor signaling regulates expression of key pluripotency genes including Oct4 and Nanog. • IRKO iPSCs show upregulation of neuronal markers during differentiation. • Adipocyte and pancreatic beta cell differentiation are perturbed in IRKO iPSCs. • Phosphoproteomics analyses confirmed the role of IR in regulation of pluripotency and developmental proteins.

A comprehensive characterization of the molecular processes controlling cell fate decisions is essential to derive stable progenitors and terminally differentiated cells that are functional from human pluripotent stem cells (hPSCs). Here, we report the use of quantitative proteomics to describe early proteome adaptations during hPSC differentiation toward pancreatic progenitors. We report that the use of unbiased quantitative proteomics allows the simultaneous profiling of numerous proteins at multiple time points, and is a valuable tool to guide the discovery of signaling events and molecular signatures underlying cellular differentiation. We also monitored the activity level of pathways whose roles are pivotal in the early pancreas differentiation, including the Hippo signaling pathway. The quantitative proteomics data set provides insights into the dynamics of the global proteome during the transition of hPSCs from a pluripotent state toward pancreatic differentiation.

A major goal of diabetes research is to develop strategies that replenish pancreatic insulin-producing beta cells. One emerging strategy is to harness pancreatic plasticity—the ability of pancreatic cells to undergo cellular interconversions—a phenomenon implicated in physiological stress and pancreatic injury. Here, we investigate the effects of inflammatory cytokine stress on the differentiation potential of ductal cells in a human cell line, in mouse ductal cells by pancreatic intraductal injection, and during the progression of autoimmune diabetes in the non-obese diabetic (NOD) mouse model. We find that inflammatory cytokine insults stimulate epithelial-to-mesenchymal transition (EMT) as well as the endocrine program in human pancreatic ductal cells via STAT3-dependent NGN3 activation. Furthermore, we show that inflammatory cytokines activate ductal-to-endocrine cell reprogramming in vivo independent of hyperglycemic stress. Together, our findings provide evidence that inflammatory cytokines direct ductal-to-endocrine cell differentiation, with implications for beta cell regeneration. ASTAR (Agency for Sci., Tech. and Research, S’pore) Published version

Summary Patients with an HNF1BS148L/+ mutation (MODY5) typically exhibit pancreatic hypoplasia. However, the molecular mechanisms are unknown due to inaccessibility of patient material and because mouse models do not fully recapitulate MODY5. Here, we differentiated MODY5 human-induced pluripotent stem cells (hiPSCs) into pancreatic progenitors, and show that the HNF1BS148L/+ mutation causes a compensatory increase in several pancreatic transcription factors, and surprisingly, a decrease in PAX6 pancreatic gene expression. The lack of suppression of PDX1, PTF1A, GATA4, and GATA6 indicates that MODY5-mediated pancreatic hypoplasia is mechanistically independent. Overexpression studies demonstrate that a compensatory increase in PDX1 gene expression is due to mutant HNF1BS148L/+ but not wild-type HNF1B or HNF1A. Furthermore, HNF1B does not appear to directly regulate PAX6 gene expression necessary for glucose tolerance. Our results demonstrate compensatory mechanisms in the pancreatic transcription factor network due to mutant HNF1BS148L/+ protein. Thus, patients typically develop MODY5 but not neonatal diabetes despite exhibiting pancreatic hypoplasia., Graphical Abstract, Highlights • HNF1BS148L/+ mutation elicits a compensatory increase in DE and pancreatic genes • MODY5-mediated pancreatic hypoplasia is independent of PDX1, PTF1A, GATA4, and GATA6 • HNF1BS148L mutation directly causes a compensatory increase in PDX1 gene expression • HNF1BS148L/+ mutation limits PAX6 expression and consequently leads to MODY5, Kulkarni, Teo, and colleagues differentiated MODY5-hiPSCs into pancreatic progenitors and demonstrated that HNF1BS148L/+ mutation elicits a compensatory mechanism in the pancreatic transcription factor network. They report that MODY5-mediated pancreatic hypoplasia is independent of PDX1, PTF1A, GATA4, and GATA6. In addition, a decrease in PAX6 gene expression may lead to MODY5 development.

Controversy has long surrounded research on pancreatic beta cell regeneration. Some groups have used nonphysiological experimental methodologies to build support for the existence of pancreatic progenitor cells within the adult pancreas that constantly replenish the beta cell pool; others argue strongly against this mode of regeneration. Recent research has reinvigorated enthusiasm for the harnessing of pancreatic plasticity for therapeutic application--for example, the transdifferentiation of human pancreatic exocrine cells into insulin-secreting beta-like cells in vitro; the conversion of mouse pancreatic acinar cells to beta-like cells in vivo via cytokine treatment; and the potential redifferentiation of dedifferentiated mouse beta cells in vivo. Here, we highlight key findings in this provocative field and provide a perspective on possible exploitation of human pancreatic plasticity for therapeutic beta cell regeneration.

Summary There is considerable interest in differentiating human pluripotent stem cells (hPSCs) into definitive endoderm (DE) and pancreatic cells for in vitro disease modeling and cell replacement therapy. Numerous protocols use fetal bovine serum, which contains poorly defined factors to induce DE formation. Here, we compared Wnt and BMP in their ability to cooperate with Activin signaling to promote DE formation in a chemically defined medium. Varying concentrations of WNT3A, glycogen synthase kinase (GSK)-3 inhibitors CHIR99021 and 6-bromoindirubin-3′-oxime (BIO), and BMP4 could independently co-operate with Activin to effectively induce DE formation even in the absence of serum. Overall, CHIR99021 is favored due to its cost effectiveness. Surprisingly, WNT3A was ineffective in suppressing E-CADHERIN/CDH1 and pluripotency factor gene expression unlike GSK-3 inhibitors or BMP4. Our findings indicate that both Wnt and BMP effectively synergize with Activin signaling to generate DE from hPSCs, although WNT3A requires additional factors to suppress the pluripotency program inherent in hPSCs., Graphical Abstract, Highlights • High dose of WNT3A cooperates with Activin to induce DE without serum • GSK-3 inhibitors, CHIR99021 and BIO, work with Activin to induce DE without serum • Wnt and BMP signaling can induce DE with comparable efficiencies without serum • WNT3A is not as effective as BMP4, CHIR99021, or BIO in suppressing pluripotency, It is yet unclear how Wnt compares with BMP signaling in promoting Activin-induced definitive endoderm formation from human pluripotent stem cells in serum-free conditions. Kulkarni and colleagues demonstrate that Wnt or BMP signaling generates Activin-induced definitive endoderm comparably and that WNT3A is ineffective at suppressing E-CADHERIN and pluripotency.

Summary The mechanisms underlying the development of complications in type 1 diabetes (T1D) are poorly understood. Disease modeling of induced pluripotent stem cells (iPSCs) from patients with longstanding T1D (disease duration ≥ 50 years) with severe (Medalist +C) or absent to mild complications (Medalist −C) revealed impaired growth, reprogramming, and differentiation in Medalist +C. Genomics and proteomics analyses suggested differential regulation of DNA damage checkpoint proteins favoring protection from cellular apoptosis in Medalist −C. In silico analyses showed altered expression patterns of DNA damage checkpoint factors among the Medalist groups to be targets of miR200, whose expression was significantly elevated in Medalist +C serum. Notably, neurons differentiated from Medalist +C iPSCs exhibited enhanced susceptibility to genotoxic stress that worsened upon miR200 overexpression. Furthermore, knockdown of miR200 in Medalist +C fibroblasts and iPSCs rescued checkpoint protein expression and reduced DNA damage. We propose miR200-regulated DNA damage checkpoint pathway as a potential therapeutic target for treating complications of diabetes.