SAT-163 Prolactin Receptor Signaling Regulates a Pregnancy-Specific Transcriptional Program in Mouse Islets

Pancreatic β-cells undergo profound hyperplasia during pregnancy to maintain maternal euglycemia. Failure to reprogram β-cells into a more replicative state has been found to underlie susceptibility to gestational diabetes (GDM). Our laboratory has recently identified a requirement for prolactin receptor (PRLR) signaling in the metabolic adaptations to pregnancy, where mice lacking β-cell PRLR (βPRLRKO) exhibit a metabolic phenotype consistent with GDM. However, the underlying transcriptional program that is responsible for the PRLR-dependent metabolic adaptations during gestation remains incompletely understood. To identify PRLR signaling gene regulatory networks and target genes within β-cells during pregnancy, we performed a transcriptomic analysis of pancreatic islets isolated from either βPRLRKO mice or littermate controls in late gestation. Gene set enrichment analysis identified Forkhead box protein M1 (Foxm1) and polycomb repressor complex 2 (PRC2) subunits Suz12 and Ezh2 as novel candidate regulators of PRLR-dependent down-regulated and up-regulated genes, respectively. GO-term pathway enrichment revealed both established and novel PRLR signaling target genes that together describe a state of increased cellular metabolism and/or proliferation. In contrast to the requirement for β-cell PRLR signaling in maintaining euglycemia during pregnancy, PRLR target genes were not induced following high-fat-diet feeding. Altogether the current study develops our understanding of genes and transcriptional regulators mediating islet adaptation during pregnancy and suggests pregnancy-specific adaptive mechanisms distinct from those activated by nutritional stress.