Functional characterization of DNA methylation in the oligodendrocyte lineage [RNASeq_development]

Myelination in the CNS is modulated by interplay between transcription factors and recruitment of chromatin modifying enzymes. Using a network built from genome-wide DNA methylation and transcriptomic profiling of sorted oligodendrocyte lineage cells that integrates oligodendrocyte-specific ChIP-Seq data, we defined a crucial role of DNA methylation in coordinating the transition between progenitor cell cycle arrest and oligodendrocyte differentiation. We further identified DNA methyltransferase 1 (DNMT1) as key regulator of oligodendrocyte survival at this transition point, as we detected severe and extensive developmental hypomyelination only in Olig1cre/+;Dnmt1flox/flox but not in Olig1cre/+;Dnmt3aflox/flox mice or in Cnpcre/+;Dnmt1flox/flox. This phenotype was characterized by decreased expression of genes regulating myelination and lipid metabolism – despite the hypomethylation observed at these genetic loci  – and upregulation of cell cycle and DNA-damage pathways. Therefore DNMT1 is a nodal point regulating proliferation, survival, and differentiation in the oligodendrocyte lineage, and is critical for cell number regulation in the developing brain. mRNA profiles of FAC-sorted P2 Pdgfra::GFP and P18 Plp1-GFP purified cell samples from mouse brains were generated by RNA-sequencing, in triplicate, using Illumina HiSeq 2000.