Disruption of neuronal RHEB signaling impairs oligodendrocyte differentiation and myelination through mTORC1-DLK1 axis

How neuronal signaling affects brain myelination remains poorly understood. We show dysregulated neuronal RHEB-mTORC1-DLK1 axis impairs brain myelination. Neuronal Rheb cKO impairs oligodendrocyte differentiation/myelination, with activated neuronal expression of the imprinted gene Dlk1. Neuronal Dlk1 cKO ameliorates myelination deficit in neuronal Rheb cKO mice, indicating that activated neuronal Dlk1 expression contributes to impaired myelination caused by Rheb cKO. The effect of Rheb cKO on Dlk1 expression is mediated by mTORC1; neuronal mTor cKO and Raptor cKO and pharmacological inhibition of mTORC1 recapitulate elevated neuronal Dlk1 expression. We demonstrate that both a secreted form of DLK1 and a membrane-bound DLK1 inhibit the differentiation of cultured oligodendrocyte precursor cells into oligodendrocytes expressing myelin proteins. Finally, neuronal expression of Dlk1 in transgenic mice reduces the formation of mature oligodendrocytes and myelination. This study identifies Dlk1 as an inhibitor of oligodendrocyte myelination and a mechanism linking altered neuronal signaling with oligodendrocyte dysfunction. [Display omitted] •Neuronal mTORC1 is required for proper brain myelination•Disrupting RHEB-mTORC1 axis activates neuronal Dlk1 expression•DLK1 is an inhibitor of oligodendrocyte differentiation and myelination•Activated neuronal Dlk1 expression contributes to hypomyelination caused by Rheb cKO Huang et al. identify the genetically imprinted gene Dlk1 as an inhibitor to oligodendrocyte myelination in vitro and in vivo. Disrupting neuronal RHEB-mTORC1 axis activates DLK1 expression that contributes to impairment in oligodendrocyte differentiation and myelination in neuronal Rheb knockout mouse.