RFX6 Maintains Gene Expression and Function of Adult Human Islet a-Cells

Mutations in the gene encoding the transcription factor regulatory factor X-box binding 6 (RFX6) are associated with human diabetes. Within pancreatic islets, RFX6 expression is most abundant in islet a-cells, and a-cell RFX6 expression is altered in diabetes. However, the roles of RFX6 in regulating gene expression, glucagon output, and other crucial human adult a-cell functions are not yet un-derstood. We developed a method for selective genetic targeting of human a-cells and assessed RFX6-dependent a-cell function. RFX6 suppression with RNA interference led to impaired a-cell exocytosis and dysregulated gluca-gon secretion in vitro and in vivo. By contrast, these phe-notypes were not observed with RFX6 suppression across all islet cells. Transcriptomics in a-cells revealed RFX6-dependent expression of genes governing nutrient sens-ing, hormone processing, and secretion, with some of these exclusively expressed in human a-cells. Mapping of RFX6 DNA-binding sites in primary human islet cells identi-fied a subset of direct RFX6 target genes. Together, these data unveil RFX6-dependent genetic targets and mechanisms crucial for regulating adult human a-cell function.