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

Abstract

The differentiation of oligodendrocyte precursor cells (OPCs) into myelinating oligodendrocytes is the prerequisite for remyelination in demyelinated disorders such as multiple sclerosis (MS). Epigenetic mechanisms, such as DNA methylation, have been suggested to control the intricate network of transcription factors involved in OPC differentiation. Yet, the exact mechanism remains undisclosed. Here, we are the first to identify the DNA-binding protein inhibitors, Id2 and Id4, as targets of DNA methylation during OPC differentiation. Using state-of-the-art epigenetic editing via CRISPR/dCas9-DNMT3a, we confirm that targeted methylation of Id2/Id4 drives OPC differentiation. Moreover, we show that in the pathological context of MS, methylation and gene expression levels of both ID2 and ID4 are altered compared to control human brain samples. We conclude that DNA methylation is crucial to suppress ID2 and ID4 during OPC differentiation, a process that appears to be dysregulated during MS. Our data do not only reveal new insights into oligodendrocyte biology, but could also lead to a better understanding of CNS myelin disorders.

From methylation to myelination: epigenomic and transcriptomic profiling of chronic inactive demyelinated multiple sclerosis lesions

“…The involvement of DNA methylation in oligodendrocyte differentiation has been investigated previously by us and other researchers (6,13,14,32). Using rodent-derived OPCs or mouse models for MS, it has been shown that the presence of DNA methylation enzymes, such as DNMT1 and DNMT3a, is crucial for oligodendrocyte differentiation during development and remyelination (14,15).…”

“…DNA methylation, for instance, is a stable yet at the same time dynamic epigenetic mark that translates environmental stimuli to alterations in gene expression and subsequent cellular behaviour. We and others have previously shown that DNA methylation contributes to physiological OPC differentiation (13, 14). In addition, DNA methylation is also required for remyelination, as shown in a mouse model for focal demyelination (15).…”

“…Human post-mortem brain tissue was obtained from the Netherlands Brain Bank (www.brainbank.nl). Chronic, inactive demyelinated white matter lesions were selected from progressive MS patients (n=10, one lesion per patient) and characterised for demyelination (Proteolipid protein [PLP - ]), inflammation (Human leukocyte antigen [HLA-DR - ], Oil Red O [ORO - ]), and presence of OPCs (Neural/glial antigen 2 [NG2 + ]) by immunohistochemistry (13). Demographic details were described before (13).…”

“…Chronic, inactive demyelinated white matter lesions were selected from progressive MS patients (n=10, one lesion per patient) and characterised for demyelination (Proteolipid protein [PLP - ]), inflammation (Human leukocyte antigen [HLA-DR - ], Oil Red O [ORO - ]), and presence of OPCs (Neural/glial antigen 2 [NG2 + ]) by immunohistochemistry (13). Demographic details were described before (13). Lesions were manually dissected from the surrounding NAWM, using the proteolipid protein (PLP) staining as a reference.…”

Molecular Mechanisms of Immunosenescene and Inflammaging: Relevance to the Immunopathogenesis and Treatment of Multiple Sclerosis

“…Intrinsic factors include age-related decline of histone deacetylation and methylation in OPCs and oligodendrocytes (by reduced HDAC class I expression), enhancing the heterochronic expression of transcriptional inhibitors [e.g., inhibitor of DNA-binding (Id)4] as well as global hypomethylation by downregulation of Dnmt1 in OPCs of aged mice (245)(246)(247). Likewise, DNA methylation of ID2/ID4 allows OPC differentiation, but their methylation levels were lower in MS lesions on human brain samples than in controls (248). Extrinsic factors from the OPC environment can also affect their differentiation.…”