The white/grey matter of spinal cord and brain are sequentially myelinated31. For example, myelinogenesis has been accomplished in the white matter of spinal cord but not the grey matter of spinal cord nor the brain by P332. We took advantage of Sox10-CreER that permits simultaneous tamoxifen-inducible targeting of SETDB1 in the OPCs, iOLs and OLs. When the mice were treated with tamoxifen at P3 (Fig. 5k), striking hypomyelination was observed in the brain and the gray matter but not the white matter of spinal cord. MBP intensity and the number of CC1+ cells in the cortices of P15 mutant mice were largely reduced compared to the controls (Fig. 5l, m). In the spinal cord, these phenotypes were only observed in the gray matter but not white matter (Fig. 5n–p). The turnover rate of myelin in the adult mice is low and most of OPCs are dormant33. Depleting Setdb1 in the OLs at P60 had no notable impact on the myelination throughout our experimental timeframe (up to P90) (Supplementary Fig. 6o-q). TdT-mediated dUTP Nick-End Labeling (TUNEL) assay failed to detect obvious
