B4GALT4 and demyelinating disease: Our study showed that Seipin deficiency reduced sphingolipid levels (HexCer, Cer, and SM species) due to downregulation its related genes, such as Cers6, B3gnt2, B4galt4 and St3gal4. As sphingolipids were mainly produced by OLs, and its dysmetabolism was implicated in demyelinating disorders [66–68], we proposed that Seipin deficiency down-regulated OPC sphingolipid metabolism, eventually disrupting OPC differentiation and causing abnormal myelination.