ISL1 controls pancreatic alpha cell fate and regulates beta cell differentiation and maturation [CUT&Tag]

Glucose homeostasis is dependent on functional pancreatic a and ß cells. Mechanisms underlying generation and maturation of these endocrine cells remain unclear. Here, we unravel the molecular mode of action of ISL1 in controlling a cell fate and endocrine differentiation in the pancreas. By combining transgenic mouse models, transcriptomic and epigenomic profiling, we uncover that elimination of Isl1 results in a diabetic phenotype with a complete loss of a cells, disrupted pancreatic islet architecture, downregulation of maturation markers of ß cells, and an enrichment in an intermediate endocrine progenitor transcriptomic profile. Mechanistically, apart from the altered transcriptome of pancreatic endocrine cells, Isl1 elimination results in altered silencing H3K27me3 histone modifications in the promoter regions of the essential genes for endocrine cell differentiation. Our results thus show that ISL1 transcriptionally and epigenetically controls a cell fate competence, and ß cell maturation, suggesting that ISL1 is a critical component for generating functional a and ß cells. Overall design: 10 biological samples pooled from two to three pancreata (biological replicates of 4 control and 6 mutant samples) were analyzed at age P9/10. Approximately 14700 cells/sample FACS-sorted tdTomato+ endocrine cells were used for CUT&Tag sequencing. At age E14.5 were analyzed 12 samples (biological replicates of 6 control and 6 mutant samples). Each sample was pooled together from five to nine pancreata ( ~ 4700 cells/sample) and used for used for CUT&Tag sequencing. Two CUT&Tag validated primary antibodies anti-H3K4me3 and anti-H3K27me3 were used. All samples were analyzed separately. Each developmental stage was enriched of one more sample were IgG antibodies were used for CUT&Tag on input cells mixed from control and mutant.