The MAPK/ERK signaling pathway has been previously identified as a main negative regulator of myelination in the demyelinating diseases multiple sclerosis (Suo et al., 2019), the Costello syndrome, and neurofibromatosis type 1, which are Rasopathies caused by germline mutations in genes encoding for members of the MAPK pathway including HRAS (HRas proto-oncogene, GTPase) (Lopez-Juarez et al., 2017; Titus et al., 2017). Here, HRAS is linked to Costello syndrome.