The Dysregulation of the <i>DLK1</i>-<i>MEG3</i> Locus in Islets From Patients With Type 2 Diabetes Is Mimicked by Targeted Epimutation of Its Promoter With TALE-DNMT Constructs

Abstract

Type 2 diabetes mellitus (T2DM) is characterized by the inability of the insulin-producing β-cells to overcome insulin resistance. We previously identified an imprinted region on chromosome 14, the <i>DLK1</i>-<i>MEG3</i> locus, as being downregulated in islets from humans with T2DM. In this study, using targeted epigenetic modifiers, we prove that increased methylation at the promoter of <i>Meg3</i> in mouse βTC6 β-cells results in decreased transcription of the maternal transcripts associated with this locus. As a result, the sensitivity of β-cells to cytokine-mediated oxidative stress was increased. Additionally, we demonstrate that an evolutionarily conserved intronic region at the <i>MEG3</i> locus can function as an enhancer in βTC6 β-cells. Using circular chromosome conformation capture followed by high-throughput sequencing, we demonstrate that the promoter of <i>MEG3</i> physically interacts with this novel enhancer and other putative regulatory elements in this imprinted region in human islets. Remarkably, this enhancer is bound in an allele-specific manner by the transcription factors FOXA2, PDX1, and NKX2.2. Overall, these data suggest that the intronic <i>MEG3</i> enhancer plays an important role in the regulation of allele-specific expression at the imprinted <i>DLK1-MEG3</i> locus in human β-cells, which in turn impacts the sensitivity of β-cells to cytokine-mediated oxidative stress.