Project description:Despite the central role of chromosomal context in gene transcription, human noncoding DNA variants are generally studied outside of their endogenous genomic location. This limits our understanding of disease-causing regulatory variants. INS promoter mutations cause recessive neonatal diabetes. We studied 60 patients with such mutations, and show that all single base mutations disrupt a CC dinucleotide, while none affect elements important for INS promoter function in episomal assays. To model CC mutations, we humanized a ~3.1 kb region of the orthologous mouse Ins2 gene. This drove cell-specific transcription and recapitulated developmental chromatin states. A CC mutant allele, however, abrogated active chromatin formation during pancreas development. A search for transcription factors that act through this element revealed that another neonatal diabetes gene product, GLIS3, had a unique pioneer-like ability to derepress INS chromatin, which was hampered by the CC mutation. Our in vivo analysis, therefore, connects two human genetic defects in a pioneering mechanism that underlies developmental activation of the INS gene. This record contains the GLIS3 ChIP-seq and input control in human pancreatic islet cells revealing GLIS3 targets in human islet tissue.
Project description:Despite the central role of chromosomal context in gene transcription, human noncoding DNA variants are generally studied outside of their genomic location. This limits our understanding of disease-causing regulatory variants. INS promoter mutations cause recessive neonatal diabetes. We show that all INS promoter point mutations in 60 patients disrupt a CC dinucleotide, whereas none affect other elements important for episomal promoter function. To model CC mutations, we humanized an ∼3.1-kb region of the mouse Ins2 gene. This recapitulated developmental chromatin states and cell-specific transcription. A CC mutant allele, however, abrogated active chromatin formation during pancreas development. A search for transcription factors acting through this element revealed that another neonatal diabetes gene product, GLIS3, has a pioneer-like ability to derepress INS chromatin, which is hampered by the CC mutation. Our in vivo analysis, therefore, connects two human genetic defects in an essential mechanism for developmental activation of the INS gene.
Project description:Global transcript profiling to identify differentially expressed skeletal muscle genes in insulin resistance, a major risk factor for Type II (non-insulin-dependent) diabetes mellitus. Compared gene expression profiles of skeletal muscle tissues from 18 insulin-sensitive versus 17 insulin-resistant equally obese, non-diabetic Pima Indians. Keywords: other
Project description:Adult stem cells represent an invaluable resource that can be harnessed for therapeutic tissue repair. Gut stem cells are accessible by biopsy and grow indefinitely in culture as organoids or cell lines. Human fetal gut can generate rare insulin-secreting cells. However, the short lifespan of gut cells, amounting to only days in situ, calls into question the feasibility of producing stable and durable gut insulin-secreting cells as a potential engraftable therapeutic. Here, we show that cultured human stomach stem cells can be directed to generate pancreatic islet-like organoids containing long-lived gastric insulin-secreting (GINS) cells that resemble pancreatic b-cells in molecular hallmarks and function. After sequential activation of the inducing factors NGN3 and PDX1-MAFA, gastric stem cells passed through a SOX4High endocrine and a GalaninHigh precursor state before adopting the b-cell fate, at efficiencies exceeding 80%. GINS cells acquired glucose-stimulated insulin secretion 10 days post differentiation and restored glucose homeostasis for over 100 days in diabetic mice after transplantation. This study establishes a promising approach to procuring autologous human insulin producers for diabetes treatment, and further expands the already considerable therapeutic opportunities for gut stem cells.
Project description:The brain is the most cholesterol-rich organ in the body, most of which comes from in situ synthesis. Here we demonstrate that in insulin-deficient diabetic mice, there is a reduction in expression of the major transcriptional regulator of cholesterol metabolism, SREBP-2, and its downstream genes in the hypothalamus and other areas of the brain, leading to a reduction in brain cholesterol synthesis and synaptosomal cholesterol content. These changes are due, at least in part, to direct effects of insulin to regulate these genes in neurons and glial cells and can be corrected by intracerebroventricular injections of insulin. Knockdown of SREBP-2 in cultured neurons causes a decrease in markers of synapse formation and reduction of SREBP-2 in the hypothalamus of mice using shRNA results in increased feeding and weight gain. Thus, insulin and diabetes can alter brain cholesterol metabolism, and this may play an important role in the neurologic and metabolic dysfunction observed in diabetes and other disease states. Hypothalamus was compared between streptozotocin (STZ)-induced diabetic, ob/ob, and control mice, with 5-6 replicates per goup.
Project description:The brain is the most cholesterol-rich organ in the body, most of which comes from in situ synthesis. Here we demonstrate that in insulin-deficient diabetic mice, there is a reduction in expression of the major transcriptional regulator of cholesterol metabolism, SREBP-2, and its downstream genes in the hypothalamus and other areas of the brain, leading to a reduction in brain cholesterol synthesis and synaptosomal cholesterol content. These changes are due, at least in part, to direct effects of insulin to regulate these genes in neurons and glial cells and can be corrected by intracerebroventricular injections of insulin. Knockdown of SREBP-2 in cultured neurons causes a decrease in markers of synapse formation and reduction of SREBP-2 in the hypothalamus of mice using shRNA results in increased feeding and weight gain. Thus, insulin and diabetes can alter brain cholesterol metabolism, and this may play an important role in the neurologic and metabolic dysfunction observed in diabetes and other disease states.
Project description:Hyperinsulinemia often precedes type 2 diabetes but its role in disease progression is unknown. Palmitoylation, a protein modification implicated in regulated exocytosis, is reversed by acyl-protein thioesterase 1 (APT1). We found altered APT1 biology in pancreatic islets from humans with type 2 diabetes, and APT1 knockdown in nondiabetic human islets caused insulin hypersecretion. Chow fed global and islet specific APT1 knockout mice had enhanced glucose tolerance due to islet autonomous increased glucose-stimulated insulin secretion. APT1 deficiency did not affect islet calcium dynamics but prolonged insulin granule fusion. Using palmitoylation proteomics, we identified Scamp1 as an APT1 substrate that localized to insulin secretory granules. Knockdown of Scamp1 caused insulin hypersecretion. APT1 deficient insulinoma cells subjected to nutrient excess had increased apoptosis, and expression of a mutated Scamp1 incapable of being palmitoylated in APT1 deficient cells rescued insulin hypersecretion and nutrient induced apoptosis. Compared to APT1 sufficient controls, high fat fed islet specific APT1 knockout mice and global APT1 deficient db/db mice showed increased -cell failure. These findings suggest that the depalmitoylation enzyme APT1 is regulated in human islets, and that APT1 deficiency causes insulin hypersecretion leading to -cell failure, modeling the evolution of some forms of human type 2 diabetes.
Project description:Insulin gene mutations are a leading cause of neonatal diabetes. They can lead to proinsulin misfolding and its retention in endoplasmic reticulum (ER). This results in increased ER-stress suggested to trigger beta-cell apoptosis. In humans, the mechanisms underlying beta-cell failure remain unclear. Here we show that misfolded proinsulin impairs developing beta-cell proliferation without increasing apoptosis. We generated iPSCs from diabetics carrying insulin mutations, engineered isogenic CRISPR-Cas9 mutation-corrected lines and differentiated them to beta-like cells using a 3D-suspension differentiation protocol. Single-cell RNA-sequencing analysis showed increased ER-stress and reduced proliferation in INS-mutant beta-like cells compared with corrected controls. Upon transplantation to mice, INS-mutant grafts presented reduced insulin secretion and aggravated ER-stress. Cell size, mTORC1 signaling, and respiratory chain subunit expression were all reduced in INS-mutant beta-like cells, yet apoptosis was not increased at any stage. Our results demonstrate that neonatal diabetes-associated INS-mutations lead to defective beta-cell mass expansion, contributing to diabetes development.
Project description:Natural and stable cell identity switches, where terminally-differentiated cells convert into different cell-types when stressed, represent a widespread regenerative strategy in animals, yet they are poorly documented in mammals. In mice, some glucagon-producing pancreatic α-cells become insulin expressers upon ablation of insulin-secreting β-cells, promoting diabetes recovery. Whether human islets also display this plasticity for reconstituting β-like cells, especially in diabetic conditions, remains unknown. Here we show that two different islet non-β-cell types, α- and γ–cells, obtained from deceased non-diabetic or diabetic human donors can be lineage-traced and induced to produce insulin and secrete it in response to glucose. When transplanted into diabetic mice, converted human α-cells reverse diabetes and remain producing insulin even after 6 months. Insulin-producing α-cells maintain α-cell markers, as seen by deep transcriptomic and proteomic characterization, and display hypo-immunogenic features when exposed to T-cells derived from diabetic patients. These observations provide conceptual evidence and a molecular framework for a mechanistic understanding of in situ cell plasticity in islet cells, as well as in other organs, as a therapy for degenerative diseases by fostering the highly-regulated intrinsic cell regeneration.