Mediator MED23 controls oligodendrogenesis and myelination by modulating Sp1/P300-directed gene programs

Gaining the molecular understanding for myelination development and regeneration has been a long-standing goal in neurological research. Mutations in the transcription cofactor Mediator Med23 subunit are often associated with intellectual disability and white matter defects, although the precise functions and mechanisms of Mediator in myelination remain unclear. In this study, we generated a mouse model carrying an Med23^Q649R mutation that has been identified in a patient with hypomyelination features. The MED23^Q649R mouse model develops white matter thinning and cognitive decline, mimicking common clinical phenotypes. Further, oligodendrocyte-lineage specific Med23 knockout mice verified the important function of MED23 in regulating central nervous system myelination and postinjury remyelination. Utilizing the in vitro cellular differentiation assay, we found that the oligodendrocyte progenitor cells, either carrying the Q649R mutation or lacking Med23, exhibit significant deficits in their capacity to differentiate into mature oligodendrocytes. Gene profiling combined with reporter assays demonstrated that Mediator Med23 controls Sp1-directed gene programs related to oligodendrocyte differentiation and cholesterol metabolism. Integrative analysis demonstrated that Med23 modulates the P300 binding to Sp1-targeted genes, thus orchestrating the H3K27 acetylation and enhancer activation for the oligodendrocyte lineage progression. Collectively, our findings identified the critical role for the Mediator Med23 in oligodendrocyte fate determination and provide mechanistic insights into the myelination pathogenesis associated with MED23 mutations.