An Activating STAT3 Mutation Causes Neonatal Diabetes through Premature Induction of Pancreatic Differentiation.

Activating germline mutations in STAT3 were recently identified as a cause of neonatal diabetes mellitus associated with beta-cell autoimmunity. We have investigated the effect of an activating mutation, STAT3 ^K392R , on pancreatic development using induced pluripotent stem cells (iPSCs) derived from a patient with neonatal diabetes and pancreatic hypoplasia. Early pancreatic endoderm differentiated similarly from STAT3 ^K392R and healthy-control cells, but in later stages, NEUROG3 expression was upregulated prematurely in STAT3 ^K392R cells together with insulin (INS) and glucagon (GCG). RNA sequencing (RNA-seq) showed robust NEUROG3 downstream targets upregulation. STAT3 mutation correction with CRISPR/Cas9 reversed completely the disease phenotype. STAT3 ^K392R -activating properties were not explained fully by altered DNA-binding affinity or increased phosphorylation. Instead, reporter assays demonstrated NEUROG3 promoter activation by STAT3 in pancreatic cells. Furthermore, proteomic and immunocytochemical analyses revealed increased nuclear translocation of STAT3 ^K392R . Collectively, our results demonstrate that the STAT3 ^K392R mutation causes premature endocrine differentiation through direct induction of NEUROG3 expression.
(Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.)