Project description:Generation of mature cells with stable functional identities is crucial for developing cell-based replacement therapies. Current global efforts to produce insulin-secreting beta-like cells to treat diabetes are hampered by the lack of tools to reliably assess cellular identity. We conducted a thorough single-cell transcriptomics meta-analysis to generate robust genesets defining the identity of human adult alpha-, beta-, gamma- and delta-cells. After extensive validation, we showed the efficacy of the novel genesets to define changes in islet cell identity, whether during embryonic development or in different experimental setups aimed at developing new functional glucose-responsive insulin-secreting cells, such as through pluripotent stem-cell differentiation or islet cell reprogramming protocols. Finally, we evaluated whether the perturbed metabolic conditions typical of diabetes influence islet cell identity. We observed that alpha-cells from diabetic donors exhibit an altered phenotype. In conclusion, these novel genesets represent valuable tools that robustly benchmark gain and loss in islet cell identity traits.
Project description:Type 2 diabetes (T2D) is associated with compromised identity of insulin-producing pancreatic islet beta (β) cells, characterized by inappropriate production of other islet cell-enriched hormones. Here we examined how hormone misexpression was influenced by the MAFA and MAFB transcription factors, closely related proteins that maintain islet cell function. Mice specifically lacking MafA in β cells demonstrated broad, population-wide changes in hormone gene expression with an overall gene signature closely resembling islet gastrin (Gast)-positive cells generated under conditions of chronic hyperglycemia and obesity. A human b cell line deficient in MAFB, but not one lacking MAFA, also produced a gastrin (GAST)-positive gene expression pattern. In addition, GAST was detected in human T2D β cells with low levels of MAFB. Moreover, evidence is provided that human MAFB can directly repress GAST gene transcription. These results support a novel, species-specific role for MafA and MAFB in maintaining adult mouse and human β cell identity, respectively, by repressing expression of Gast/GAST and other non-b cell hormones.
Project description:<h4><strong>AIMS/HYPOTHESIS: </strong>Metabolic dysregulation may precede the onset of type 1 diabetes. However, these metabolic disturbances and their specific role in disease initiation remain poorly understood. In this study, we examined whether children who progress to type 1 diabetes have a circulatory polar metabolite profile distinct from that of children who later progress to islet autoimmunity but not type 1 diabetes and a matched control group.</h4><h4><strong>METHODS: </strong>We analysed polar metabolites from 415 longitudinal plasma samples in a prospective cohort of children in three study groups: those who progressed to type 1 diabetes; those who seroconverted to one islet autoantibody but not to type 1 diabetes; and an antibody-negative control group. Metabolites were measured using two-dimensional GC high-speed time of flight MS.</h4><h4><strong>RESULTS: </strong>In early infancy, progression to type 1 diabetes was associated with downregulated amino acids, sugar derivatives and fatty acids, including catabolites of microbial origin, compared with the control group. Methionine remained persistently upregulated in those progressing to type 1 diabetes compared with the control group and those who seroconverted to one islet autoantibody. The appearance of islet autoantibodies was associated with decreased glutamic and aspartic acids.</h4><h4><strong>CONCLUSIONS/INTERPRETATION: </strong>Our findings suggest that children who progress to type 1 diabetes have a unique metabolic profile, which is, however, altered with the appearance of islet autoantibodies. Our findings may assist with early prediction of the disease.</h4>
Project description:Understanding distinct gene expression patterns of normal adult and developing fetal human pancreatic a and b cells is crucial for developing stem cell therapies, islet regeneration strategies, and therapies designed to increase b cell function in patients with diabetes (type 1 or 2). Toward that end, we have developed methods to highly purify a, b, and d cells from human fetal and adult pancreata by intracellular staining for the cell-specific hormone content, sorting the sub-populations by flow cytometry and, using next generation RNA sequencing, we report on the detailed transcriptomes of fetal and adult a and b cells. We observed that human islet composition was not influenced by age, gender, or body mass index and transcripts for inflammatory gene products were noted in fetal b cells. In addition, within highly purified adult glucagon-expressing a cells, we observed surprisingly high insulin mRNA expression, but not insulin protein expression. This transcriptome analysis from highly purified islet a and b cell subsets from fetal and adult pancreata offers clear implications for strategies that seek to increase insulin expression in type 1 and type 2 diabetes. RNA-sequencing of highly purified human adult and fetal islet cell subset was performed using our newly developed method. Using this data, we can study and compare the detailed transcriptome or alpha and beta cells during development.
Project description:Blood glucose levels are tightly controlled by the coordinated action of at least five cell types constituting pancreatic islets. Changes in the proportion and/or function of these cells are associated with genetic and molecular pathophysiology of monogenic, type 1, and type 2 diabetes (T2D). Cellular heterogeneity impedes precise understanding of the molecular components of each islet cell type that govern islet dysfunction, particularly the less abundant delta and gamma/pancreatic polypeptide (PP) cells. Here, we report single cell transcriptomes for 617 islet cells after profiling ~1000 cells from non-diabetic (ND) and T2D human organ donors. Analyses of non-diabetic single cell transcriptomes identified distinct alpha, beta, delta, and PP/gamma cell-type signatures. Genes linked to rare and common forms of islet dysfunction and diabetes were expressed in the delta and PP/gamma cell types. Moreover, this study revealed that delta cells specifically express receptors that receive and coordinate systemic cues from the leptin, ghrelin, and dopamine signaling pathways implicating them as integrators of central and peripheral metabolic signals into the pancreatic islet. Finally, single cell transcriptome profiling revealed genes differentially regulated between T2D and ND alpha, beta, and delta cells that were undetectable in paired whole islet analyses. This study thus identifies fundamental cell type-specific features of pancreatic islet (dys)function and provides a critical resource for comprehensive understanding of islet biology and diabetes pathogenesis. Grant ID: Award No. W81XWH-16-1-0130 Grant title: Peer Reviewed Medical Research Program Funding Source: Assistant Secretary of Defense for Health Affairs Affiliation: Jackson Laboratory for Genomic Medicine, Farmington, CT Name: Michael Stitzel
Project description:Pancreatic islets are essential for maintaining physiological blood glucose levels, and declining islet function is a hallmark of type 2 diabetes. Here we employ mass spectrometry (MS)-based proteomics to systematically analyse purified islets from 9 genetic or diet-induced mouse models representing a broad cross-section of metabolic health. Quantifying the islet proteome to a depth of >11,500 proteins, this study represents the most detailed analysis of islet proteins to date. Our data highlight that the vast majority of islet proteins are expressed in all strains and diets, but more than half of the proteins vary in expression levels. Associating these varied protein expression levels on an individual animal basis with individual phenotypic measures reveals islet mitochondrial function as a major positive indicator of metabolic health. This compendium of strain-specific and dietary changes to mouse islet proteomes represents a comprehensive resource for basic and translational islet cell biology.
Project description:Blood glucose levels are tightly controlled by the coordinated action of at least five cell types constituting pancreatic islets. Changes in the proportion and/or function of these cells are associated with genetic and molecular pathophysiology of monogenic, type 1, and type 2 diabetes (T2D). Cellular heterogeneity impedes precise understanding of the molecular components of each islet cell type that govern islet dysfunction, particularly the less abundant delta and gamma/pancreatic polypeptide (PP) cells. Here, we report single cell transcriptomes for 617 islet cells after profiling ~1000 cells from non-diabetic (ND) and T2D human organ donors. Analyses of non-diabetic single cell transcriptomes identified distinct alpha, beta, delta, and PP/gamma cell-type signatures. Genes linked to rare and common forms of islet dysfunction and diabetes were expressed in the delta and PP/gamma cell types. Moreover, this study revealed that delta cells specifically express receptors that receive and coordinate systemic cues from the leptin, ghrelin, and dopamine signaling pathways implicating them as integrators of central and peripheral metabolic signals into the pancreatic islet. Finally, single cell transcriptome profiling revealed genes differentially regulated between T2D and ND alpha, beta, and delta cells that were undetectable in paired whole islet analyses. This study thus identifies fundamental cell type-specific features of pancreatic islet (dys)function and provides a critical resource for comprehensive understanding of islet biology and diabetes pathogenesis. Grant ID: Award No. W81XWH-16-1-0130 Grant title: Peer Reviewed Medical Research Program Funding Source: Assistant Secretary of Defense for Health Affairs Affiliation: Jackson Laboratory for Genomic Medicine, Farmington, CT Name: Michael Stitzel
Project description:We anticipated that the identification of cis-regulatory regions active in pancreatic islets would help increase our understanding of islet biology and the pathology of diabetes. Towards this end we used histone H3 lysine 4 monomethylation-based nucleosome predictions genome-wide, in conjunction with binding data for PDX1, FOXA2, MAFA, and NEUROD1, to identify 3,654 putative enhancers that are H3K4me1-enriched uniquely in islets as compared to 14 other tissue or cell-types. We show that these islet-specific enhancers are associated with genes with significantly higher islet specificity than genes associated with non-specific enhancers. Further, islet-specific enhancers were not enriched for typical active or repressive histone methylations in embryonic stem cells and liver, suggesting they are formed by de novo histone methylation during pancreas development. We also identify a subset of enhancers bivalently marked by both H3K4me1 and H3K27me3 in adult pancreatic islets. Further, we show that islet-specific enhancers triple- or quadruple- bound by PDX1, MAFA, NEUROD1 and/or FOXA2 are associated with genes with particularly high islet-specificity, and that these loci are enriched in regions with functional activity in islet cell types. Finally, we demonstrate that cytokines reduce H3K4me1 enrichment levels at selected triple- or quadruple-bound islet-specific enhancers, suggesting that epigenetic changes may contribute to cytokine-induced b-cell dysfunction. In conjunction with data from Hoffman et al Genome Research 2010, an analysis of histone modifications and transcription factor binding sites to identify enhancer regions
Project description:Pancreatic islet cells are critical for maintaining normal blood glucose levels and their malfunction underlies diabetes development and progression. We used single-cell RNA sequencing to determine the transcriptomes of 1,492 human pancreatic α-, β-, δ- and PP cells from non-diabetic and type 2 diabetes organ donors. We identified cell type specific genes and pathways as well as 245 genes with disturbed expression in type 2 diabetes. Importantly, 92% of the genes have not previously been associated with islet cell function or growth. Comparison of gene profiles in mouse and human α- and β-cells revealed species-specific expression. All data are available for online browsing and download and will hopefully serve as a resource for the islet research community.