Project description:Remarkable advancements in protocol development have been achieved to manufacture insulin-secreting islets from human pluripotent stem cells. Distinct from current approaches, we devised a tunable strategy to generate islet spheroids enriched for major islet cell types by incorporating PDX1+ cell budding morphogenesis into the differentiation process of staged transcriptional programming. In this process that appears to mimic normal islet morphogenesis, the differentiating islet spheroids self-organize with endocrine cells that are intermingled or arranged in a core-mantle architecture, accompanied with functional heterogeneity. Through in vitro modelling of human pancreas development, we illustrate the importance of PDX1 in eliciting cell budding morphogenesis, and the requirement for EphB3/4 signaling. We show how RFX6 deficiency affects pancreatic patterning and uncover an expected role of RFX6 in early pancreas morphology. The tunable differentiation system and stem cell-derived islet models described in this work may facilitate addressing fundamental questions in islet biology and probing human pancreas diseases.
Project description:Remarkable advances in protocol development have been achieved to manufacture insulin-secreting islets from human pluripotent stem cells (hPSCs). Distinct from current approaches, we devised a tunable strategy to generate islet spheroids enriched for major islet cell types by incorporating PDX1+ cell budding morphogenesis into staged differentiation. In this process that appears to mimic normal islet morphogenesis, the differentiating islet spheroids organize with endocrine cells that are intermingled or arranged in a core-mantle architecture, accompanied with functional heterogeneity. Through in vitro modelling of human pancreas development, we illustrate the importance of PDX1 and the requirement for EphB3/4 signaling in eliciting cell budding morphogenesis. Using this new approach, we model Mitchell-Riley syndrome with RFX6 knockout hPSCs illustrating unexpected morphogenesis defects in the differentiation towards islet cells. The tunable differentiation system and stem cell-derived islet models described in this work may facilitate addressing fundamental questions in islet biology and probing human pancreas diseases.
Project description:In Ciona intestinalis, the palps consist of three conical protrusions within a field of thickened epithelium that form late in embryogenesis as tailbuds mature into larvae. The palp protrusions express the LIM-homeodomain transcription factor Islet. Protrusion occurs through differential cell elongation, likely mediated by Islet, as we find that ectopic expression of Islet is sufficient to promote cell elongation. FGF signaling is required for both Islet expression and palp morphogenesis. Importantly, we show that Islet expression can rescue the palp-deficient phenotype that results from inhibition of FGF signaling. We conclude that Islet is a key regulatory factor governing morphogenesis of the palps. It is conceivable that Islet is also essential for the cellular morphogenesis of placode-derived sensory neurons in vertebrates. Islet expression can rescue the palp-deficient phenotype that results from inhibition of FGF signaling, and conclude that Islet is a key regulatory factor governing morphogenesis of the palps. Three biological replicates were analyzed for both sample types (Fox positive and Negative).
Project description:Transcription factors positively and/or negatively impact gene expression by recruiting coregulatory factors, which interact through protein-protein binding. Here we demonstrate that mouse pancreas size and islet β cell function are controlled by the ATP-dependent Swi/Snf chromatin-remodeling coregulatory complex that physically associates with Pdx1, a diabetes-linked transcription factor essential to pancreatic morphogenesis and adult islet-cell function and maintenance. Early embryonic deletion of just the Swi/Snf Brg1 ATPase subunit reduced multipotent pancreatic progenitor cell proliferation and resulted in pancreas hypoplasia. In contrast, removal of both Swi/Snf ATPase subunits, Brg1 and Brm, were required to compromise adult islet β cell activity, which included whole animal glucose intolerance, hyperglycemia and impaired insulin secretion. Notably, lineage-tracing analysis revealed that these Swi/Snf deficient β cells lost the ability to produce insulin and other key metabolic genes, yet the expression levels of many essential islet-enriched transcription factors were unaffected. Swi/Snf was necessary for Pdx1 binding to the insulin enhancer, demonstrating the importance of this association in mediating chromatin accessibility. These results illustrate how fundamental the Pdx1:Swi/Snf coregulator complex is in the pancreas and we discuss how disrupting their association could influence Type 1 and Type 2 diabetes susceptibility.
Project description:In Ciona intestinalis, the palps consist of three conical protrusions within a field of thickened epithelium that form late in embryogenesis as tailbuds mature into larvae. The palp protrusions express the LIM-homeodomain transcription factor Islet. Protrusion occurs through differential cell elongation, likely mediated by Islet, as we find that ectopic expression of Islet is sufficient to promote cell elongation. FGF signaling is required for both Islet expression and palp morphogenesis. Importantly, we show that Islet expression can rescue the palp-deficient phenotype that results from inhibition of FGF signaling. We conclude that Islet is a key regulatory factor governing morphogenesis of the palps. It is conceivable that Islet is also essential for the cellular morphogenesis of placode-derived sensory neurons in vertebrates. Islet expression can rescue the palp-deficient phenotype that results from inhibition of FGF signaling, and conclude that Islet is a key regulatory factor governing morphogenesis of the palps.
Project description:To get a more complete picture of the transcriptional changes associated with Pdx1 loss in ?-cells, we conducted an mRNA microarray comparing normal islet ?-cells and a-cells to the reprogrammed cells from PKO mice. Islet beta cells are from mice which has a single copy of Pdx1 flox (Pdx1L/+) allele, but is considered normal based on normal islet morphology, gene profiling, and euglycemic status. We chose to use heterozygous mice as control to avoid the litter effect. Islet alpha cells are from normal mice. To enrich for genes directly affected by Pdx1 loss, we chose the early time-point for analysis of PKO mice (5d after TAM administration). Control mRNA profiling was performed on FACS sorted islet YFP+ ?-cells and a-cells obtained from 2 month-old glucagon-Cre; RosaYFP and RIP-CreER; Pdx1fl/+, RosaYFP mice, respectively.
Project description:To get a more complete picture of the transcriptional changes associated with Pdx1 loss in β-cells, we conducted an mRNA microarray comparing normal islet β-cells and a-cells to the reprogrammed cells from PKO mice. Islet beta cells are from mice which has a single copy of Pdx1 flox (Pdx1L/+) allele, but is considered normal based on normal islet morphology, gene profiling, and euglycemic status. We chose to use heterozygous mice as control to avoid the litter effect. Islet alpha cells are from normal mice.
Project description:Identification of protein intreactions for the synaptotagmin 13 protein from MDCK cells by BioID-based proximity labelling and LFQ mass spectrometry. Epithelial cell egression is important for organ development and cell differentiation, but also drives cancer metastasis. The tightly connected pancreatic epithelial differentiation and morphogenesis generate islets of Langerhans. However, the morphogenetic drivers and molecular mechanisms are largely unresolved. Here we identify the uncharacterized Synaptotagmin 13 (Syt13) as a major regulator of endocrine cell egression and islet morphogenesis and differentiation. We detected upregulation of Syt13 in endocrine precursors that associates with increased expression of several unique cytoskeletal components. High-resolution imaging reveals a previously unidentified apical-basal to front-rear repolarization during endocrine cell egression. Strikingly, Syt13 directly interacts with acetylated tubulin and phosphoinositide phospholipids to be recruited to the leading edge of egressing cells. Knockout of Syt13 discloses the impairment in endocrine cell egression and skews the α-to-β-cell ratio. At mechanistic levels, Syt13 regulates protein endocytosis to remodel the basement membrane and modulate cell-matrix adhesion at the leading edge of egressing endocrine cells. Altogether, these findings implicate that Ca2+-independent atypical Syt13 vesicular protein functions in regulating cell polarity to orchestrate endocrine cell egression and tissue morphogenesis.
Project description:Identification of protein complexes for the synaptotagmin 13 protein from MDCK cells by Strep affinity purificaiton and LFQ mass spectrometry. Epithelial cell egression is important for organ development and cell differentiation, but also drives cancer metastasis. The tightly connected pancreatic epithelial differentiation and morphogenesis generate islets of Langerhans. However, the morphogenetic drivers and molecular mechanisms are largely unresolved. Here we identify the uncharacterized Synaptotagmin 13 (Syt13) as a major regulator of endocrine cell egression and islet morphogenesis and differentiation. We detected upregulation of Syt13 in endocrine precursors that associates with increased expression of several unique cytoskeletal components. High-resolution imaging reveals a previously unidentified apical-basal to front-rear repolarization during endocrine cell egression. Strikingly, Syt13 directly interacts with acetylated tubulin and phosphoinositide phospholipids to be recruited to the leading edge of egressing cells. Knockout of Syt13 discloses the impairment in endocrine cell egression and skews the α-to-β-cell ratio. At mechanistic levels, Syt13 regulates protein endocytosis to remodel the basement membrane and modulate cell-matrix adhesion at the leading edge of egressing endocrine cells. Altogether, these findings implicate that Ca2+-independent atypical Syt13 vesicular protein functions in regulating cell polarity to orchestrate endocrine cell egression and tissue morphogenesis.