Precise regulation of β cell function is crucial for maintaining blood glucose homeostasis. Pax6 is an essential regulator of β cell-specific factors like insulin and Glut2. Studies in the developing eye suggest that Pax6 interacts with Mitf to regulate pigment cell differentiation. Here we show that Mitf, like Pax6, is expressed in all pancreatic endocrine cells during mouse postnatal development and in the adult islet. A Mitf loss of function mutation results in improved glucose tolerance and enhanced insulin secretion, but no increase in β cell mass in adult mice. Mutant β cells secrete more insulin in response to glucose than wild-type cells, suggesting that Mitf is involved in regulating β cell function. In fact, the transcription of genes critical for maintaining glucose homeostasis (insulin, Glut2) and β cell formation and function (Pax4, Pax6) is significantly upregulated in Mitf mutant islets. The increased Pax6 expression may cause the improved β cell function observed in Mitf mutant animals as it activates insulin and Glut2 transcription. Chromatin immunoprecipitation analysis shows that Mitf binds to Pax4 and Pax6 regulatory regions suggesting that Mitf represses their transcription in wild-type β cells. We demonstrate that Mitf directly regulates Pax6 transcription and controls β cell function.
- Received October 22, 2012.
- Accepted April 15, 2013.
- © 2013 by the American Diabetes Association.
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