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PAX4 loss of function alters human endocrine cell development and influences diabetes risk [dataset 2]

ABSTRACT: Diabetes is a major chronic disease with an excessive healthcare burden on society. A coding variant (p.Arg192His) in the transcription factor PAX4 is uniquely and reproducibly associated with altered risk for type 2 diabetes (T2D) in East Asian populations, whilst rare PAX4 alleles have been proposed to cause monogenic diabetes8. In mice, Pax4 is essential for beta cell formation but neither the role of diabetes-associated variants in PAX4 nor PAX4 itself on human beta cell development and/or function are known. Here, we demonstrate that non-diabetic carriers of either the PAX4 p.Arg192His or a newly identified p.Tyr186X allele exhibit decreased pancreatic beta cell function. In the human beta cell model, EndoC-βH1, PAX4 knockdown led to impaired insulin secretion, reduced total insulin content and altered hormone gene expression. Deletion of PAX4 in isogenic human induced pluripotent stem cell (hiPSC)-derived beta-like cells resulted in de-repression of alpha cell gene expression whilst in vitro differentiation of hiPSCs from carriers of PAX4 p.192His and p.186X alleles exhibited increased polyhormonal endocrine cell formation and reduced insulin content. In silico and in vitro studies showed that these PAX4 alleles cause either reduced PAX4 expression or function. Correction of the diabetes-associated PAX4 alleles reversed these phenotypic changes. Together, we demonstrate the role of PAX4 in human endocrine cell development, beta cell function and its contribution to type 2 diabetes risk.

ORGANISM(S): Homo sapiens

PROVIDER: GSE203264 | GEO | 2023/08/05

REPOSITORIES: GEO

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Project description:Objective: Enteroendocrine cells (EECs) survey the gut luminal environment and co-ordinate hormonal, immune and neuronal responses to it. They exhibit well characterized physiological roles ranging from the control of local gut function to whole body metabolism, but little is known regarding the regulatory networks controlling their differentiation, especially in human gut. The small molecule Isoxazole-9 (ISX-9) has been shown to stimulate neuronal and pancreatic beta-cell differentiation, both closely related to EEC differentiation. Our aim was to use ISX-9 as a tool to explore EEC differentiation. Methods: We investigated the effects of ISX-9 on EEC differentiation in mouse and human intestinal organoids, using real time quantitative PCR, fluorescent activated cell sorting, immunostaining and single cell RNA sequencing. Results: ISX-9 increased the number of neurogenin3 (Ngn3) positive endocrine progenitor cells and upregulated NeuroD1 and Pax4, transcription factors which play roles in mouse EEC specification. Single cell analysis revealed induction of Pax4 expression in a developmentally late Ngn3+ population of cells and potentiation of genes associated with progenitors biased towards serotonin-producing enterochromaffin (EC) cells. This coincided with enrichment of organoids with functional EC cells which was partly dependent on stimulation of calcium signalling in a population of cells residing outside the crypt base. Inducible Pax4 overexpression, in ileal organoids, uncovered its importance as a component of early human endocrine specification and highlighted the potential existence of two major endocrine lineages, the early appearing enterochromaffin lineage and the later developing peptidergic lineage which contains classical gut hormone cell types. Conclusion: Our data provide proof-of-concept for the controlled manipulation of specific endocrine lineages with small molecules, whilst also shedding new light on human EEC differentiation and its similarity to mouse. Given their diverse roles, understanding endocrine lineage plasticity and its control could have multiple therapeutic implications.

Project description:Purpose: The complete understanding of how genetic and epigenetic components control beta cell differentiation and function is key to the discovery of novel therapeutic approaches to prevent beta cell dysfunction and failure in the progression of type 2 diabetes. Our goal was to elucidate the role of histone deacetylase SIRT6 in beta-cell development and homeostasis. Methods: The Sirt6 endocrine progenitor cell conditional knockout (EKO) and beta-cell-specific knockout (BKO) mice were generated using the Cre-loxP system. Mice were assayed for islet morphology, glucose tolerance, glucose-stimulated insulin secretion, and susceptibility to streptozotocin. Transcriptional regulatory functions of SIRT6 in primary islets were evaluated by RNA-seq analysis. RT-qPCR and immunoblot were used to verify and investigate the gene expression changes. Chromatin occupancies of SIRT6, H3K9Ac, H3K56Ac, and active RNA Polymerase II were evaluated by chromatin immunoprecipitation. Results: Deletion of Sirt6 in pancreatic endocrine progenitor cells did not affect endocrine morphology, beta cell mass, or insulin production, but did result in glucose intolerance and defective glucose-stimulated insulin secretion in mice. Conditional deletion of Sirt6 in adult beta cells reproduced the insulin secretion defect. Loss of Sirt6 resulted in aberrant upregulation of TXNIP. SIRT6 deficiency led to increased accumulations of H3K9Ac, H3K56Ac, and active RNA polymerase II at the promoter region of Txnip. SIRT6-deficient beta cells exhibited a time-dependent increase of H3K9Ac, H3K56Ac, and TXNIP levels. Furthermore, beta-cell-specific SIRT6 deficient mice showed increased sensitivity to streptozotocin. Conclusions: Our results reveal that SIRT6 suppresses Txnip expression in beta-cells via deacetylation of histone H3 and plays a critical role in maintaining beta-cell function and viability. Agents that preserve SIRT6 activity may be beneficial for preventing the progression of type 2 diabetes.

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PAX4 loss of function alters human endocrine cell development and influences diabetes risk [dataset 2]

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