<b>RFX6 </b><b>maintains </b><b>gene expression and function of adult human islet </b><b>a</b><b> cells</b>

<p dir="ltr"><b>ABSTRACT</b></p><p dir="ltr">Mutations in the gene encoding the transcription factor RFX6 are associated with human diabetes mellitus. Within pancreatic islets, <i>RFX6</i> expression is most abundant in islet a cells, and<i> </i>a cell <i>RFX6 </i>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 understood. We developed a method for selective genetic targeting of human a cells and assessed <i>RFX6</i>-dependent a cell function. <i>RFX6 </i>suppression with RNA interference led to impaired a cell exocytosis and dysregulated glucagon secretion <i>in vitro</i> and <i>in vivo</i>. By contrast, these phenotypes were not observed with <i>RFX6 </i>suppression across all islet cells. Transcriptomics in a cells revealed <i>RFX6</i>-dependent expression of genes governing nutrient sensing, 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 identified 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.</p><p><br></p><p dir="ltr"><b>ARTICLE HIGHLIGHTS</b></p><p dir="ltr">· <i>RFX6</i> is expressed in all islet endocrine cell types and is dysregulated in multiple forms of diabetes, but its function has not yet been delineated in a cells.</p><p dir="ltr">· We used specific targeting of shRNA-mediated suppression of <i>RFX6</i> in primary human a cells to unveil glucagon secretion phenotypes.</p><p dir="ltr">· RFX6 is required in adult human a cells to maintain gene regulation and hallmark functions, including regulated glucagon secretion.</p><p dir="ltr">· RNA-sequencing and CUT&RUN studies reveal distinct RFX6 genetic targets in adult human a and b cells.</p>