202-OR: Early De Novo DNA Methylation Patterning Regulates Adult Beta-Cell Function and Survival Programs

DNA methylation is an important epigenetic mechanism that controls transcriptional programs to direct cell phenotype. Dynamic, stage-specific changes in DNA methylation coordinate the gene-expression patterns associated with cell differentiation throughout development. Our prior work has shown that the establishment of new DNA methylation patterns is essential for functional maturation of beta cells in postnatal life, while maintenance of existing methylation patterns sustains beta cell identity. While maintenance of DNA methylation in pancreatic progenitors is essential for their survival during differentiation, the requirement for new DNA methylation patterns in pancreatic progenitors has not been investigated. To address this, we generated pancreatic progenitor specific ablation of the de novo DNA methyltransferase, Dnmt3a, an enzyme that establishes new DNA methylation patterns, using Pdx1-Cre (Dnmt3aPKO) . RNA-sequencing of the Dnmt3aPKO islets reveals that early loss of Dnmt3a alters the beta cell identity, function, and survival programs. In addition, we observe the upregulation of genes associated with dopamine signaling and disruption of imprinted gene expression in the KO islets. Several of these gene-expression changes are distinct from those observed upon beta cell specific ablation of Dnmt3a, suggesting the unique contribution of early patterning to adult beta cell phenotype. Genome-wide profiling of DNA methylation patterns using reduced representation bisulfite sequencing (RRBS) in the Dnmt3aPKO islets points to disruption of similar programs associated with cell identity and function. These data also reveal interesting differences in the DNA methylation patterns in male and female Dnmt3aPKO mice. Collectively, our data suggest that stage specific DNA methylation patterning during beta cell differentiation controls specific aspects of the mature beta cell phenotype.