Rfx6 maintains the functional identity of adult pancreatic beta cells

Increasing evidence suggests that loss of beta cell characteristics may cause insulin secretory deficiency in diabetes, but the underlying mechanisms remain unclear. Here, we show that Rfx6, whose mutation leads to neonatal diabetes in humans, is essential to maintain key features of functionally mature beta cells in mice. Rfx6 loss in adult beta cells leads to glucose intolerance, impaired beta cell glucose sensing, and defective insulin secretion. This is associated with reduced expression of core components of the insulin secretion pathway, including glucokinase, the Abcc8/SUR1 subunit of KATP channels and voltage-gated Ca(2+) channels, which are direct targets of Rfx6. Moreover, Rfx6 contributes to the silencing of the vast majority of "disallowed" genes, a group usually specifically repressed in adult beta cells, and thus to the maintenance of beta cell maturity. These findings raise the possibility that changes in Rfx6 expression or activity may contribute to beta cell failure in humans.