Identification of distinct functions of GLIS3 in β-cell generation critical to prevention of neonatal diabetes

GLIS3 plays a critical role in pancreatic β cells and diabetes, being one of only a few genes implicated in Type 1, Type 2, and Gestational diabetes. In addition to β cells, GLIS3 is expressed embryonically in bipotent and proendocrine progenitor cells, suggesting a role in endocrine lineage development in mice. We hypothesize that GLIS3 is playing important roles in endocrine development as well as during β cell differentiation. We utilized single cell RNA-sequencing at three different timepoints (embryonic day (e)13.5, e15.5, and e18.5) and single nucleus (sn)ATAC-sequencing at e15.5 in both wild type (WT) and <i>Glis3</i> Knockout (<i>Glis3</i>KO) mouse embryos. This analysis revealed that the numbers of bipotent, proendocrine progenitor, and all subsequent endocrine cells were proportionately reduced in <i>Glis3</i>KO mice. Additionally, loss of GLIS3 function generates a unique subpopulation of cells that fail to upregulate <i>Ins2</i> transcription and downregulate expression of several ribosomal and oxidative phosphorylation genes normally repressed during preβ to β cell differentiation. Our study therefore shows that GLIS3 regulates two distinct stages: the embryonic generation/differentiation of bipotent cells and the differentiation of preβ to β cells. Dysregulation of these two stages provides a causal mechanism for the development of neonatal diabetes in GLIS3-deficiency.