DEGS1 and leukodystrophy, hypomyelinating, 18: HLD-18 patients display reduced myelin sheath thickness in peripheral nerves, and knockdown of DEGS1 function in zebrafish reduces the number of myelin basic protein-positive oligodendrocytes (Karsai et al., 2019; Pant et al., 2019), suggesting DEGS1 regulates Schwann cell and oligodendrocyte development.