Multi-site Neurogenin3 Phosphorylation Controls Pancreatic Endocrine Differentiation

The proneural transcription factor Neurogenin3 (Ngn3) plays a critical role in pancreatic endocrine cell differentiation, although regulation of Ngn3 protein is largely unexplored. Here we demonstrate that Ngn3 protein undergoes cyclin-dependent kinase (Cdk)-mediated phosphorylation on multiple serine-proline sites. Replacing wild-type protein with a phosphomutant form of Ngn3 increases α cell generation, the earliest endocrine cell type to be formed in the developing pancreas. Moreover, un(der)phosphorylated Ngn3 maintains insulin expression in adult β cells in the presence of elevated c-Myc and enhances endocrine specification during ductal reprogramming. Mechanistically, preventing multi-site phosphorylation enhances both Ngn3 stability and DNA binding, promoting the increased expression of target genes that drive differentiation. Therefore, multi-site phosphorylation of Ngn3 controls its ability to promote pancreatic endocrine differentiation and to maintain β cell function in the presence of pro-proliferation cues and could be manipulated to promote and maintain endocrine differentiation in vitro and in vivo.This work was supported by the MRC Research GrantMR/K018329/1; the Rosetrees Trust (to A.P. and R.A.); the MRC Research Grant MR/L021129/1 and core support from the Wellcome Trust and the MRC Cambridge Stem Cell Institute (to A.P. and F.A.); the MRC Doctoral Training Awards (to L.M., L.H., and M.S.); the CRUK studentship (to C. Hurley); the Wellcome Trust 098357/Z/12/Z (to B.D.S. and R.A.); and the Wellcome Trust 097922/Z/11/Z and the Clinical Research Infrastructure Single-Cell Facility (MR/M008975/1) (to B.G.). D.W. and R.K. are CRUK funded; G.E. is CRUK A12077 funded. M.H. is a Sir Henry Dale fellow and is supported by the Wellcome Trust 104151/Z/14/A and the Royal Society