DNA methylation regulates the expression of the negative transcriptional regulators ID2 and ID4 during OPC differentiation.

Abstract

* Equal contribution The differentiation of oligodendrocyte precursor cells (OPCs) into myelinating oligodendrocytes is a well-established process, coordinated by an intricate network of transcriptional regulators. Epigenetic mechanisms, such as DNA methylation, have been suggested to control this network. The exact mechanism by which DNA methylation influences the myelin regulatory pathway during OPC differentiation remains poorly elucidated though. Here, we identified both the DNA-binding protein inhibitors, Id2 and Id4, as the main targets of DNA methylation during the differentiation of murine OPCs into mature oligodendrocytes. We show that these inhibitory transcriptional regulators display hypermethylation, concomitant with decreased expression levels, as OPCs differentiate into oligodendrocytes in vitro. Furthermore, by making use of epigenetic editing by CRISPR/dCas9-DNMT3a, we confirm that targeted methylation of Id2/Id4 boosts OPC differentiation and Mbp, Plp and Mobp gene expression in vitro. Finally, we show that in a pathological context such as multiple sclerosis (MS), methylation as well as gene expression levels of both ID2 and ID4 are altered compared to non-neurologic control human brain samples. Taken together, our data reveal that DNA methylation regulates Id2/Id4 within the transcriptional network that drives myelination during oligodendrocyte development, which does not only reveal new insights into oligodendrocyte biology, but could also lead to a better understanding of CNS myelin disorders, such as MS.