Pancreatic islet ß-cell subtypes are derived from biochemically-distinct and nutritionally-regulated islet progenitors
Endocrine islet beta cells comprise heterogenous cell subsets. Yet the origin, stability, and physiological significance of these subsets remain largely unknown. Using combinatorial cell lineage tracing, scRNA-seq, and DNA methylation analysis, we show here that embryonic islet progenitors with differential gene expression and DNA methylation produce stable beta-cell subtypes of different function and viability in adult mice. Differentially expressed genes, including the Myt transcription factors, voltage-gated channels, and Ca2+-sensor synaptotagmins, contribute to the functional differences of these subtypes. Maternal overnutrition, a major diabetes risk factor, reduces the proportion of endocrine progenitors of the better-functionality beta-cell subtype. Intriguingly, the gene signature that defines mouse beta-cell subtypes can reliably divide human cells into two populations, with the proportion of better-functionality beta cells reduced in diabetic donors. These results establish that some beta-cell subtypes are determined via DNA methylation in embryonic islet progenitors, which is regulated by diabetes-causing maternal factors. The implication is that modulating DNA methylation in islet progenitors can be explored to improve beta-cell function in the prevention and therapy of diabetes. Overall design: Mice with a genotype of Myt1cCre; Ngn3nCre; Ai9 (MNA) will be derived via routine crossing.  This allows the activation of islet progenitors that co-express Ngn3 and Myt1 to be labeled with tdTomato permanently. When MNA mice were at postnatal day 2 (P2) and 2-months, they will be used for islet isolation. Islets were then washed with Ca2+/Mg2+ free HBSS and dissociated into single cells (~3-5 minutes). They were then used for InDrop RNAseq.