L1CAM and congenital hydrocephalus: The genes responsible for X-linked human congenital hydrocephalus are L1CAM (L1 protein), located at Xq28 (Jouet et al., 1993; Adle-Biassette et al., 2013), and AP1S2 (Shaheen et al., 2017; Marguet et al., 2021).