AP1S2 and congenital hydrocephalus: AP1S2 encodes the sigma 2 subunit of the AP1 Adaptin protein for regulating lysosomal protein sorting, and the mutation of AP1S2 was reported to relate to X-linked congenital hydrocephalus through aberrant vesicle trafficking (Kousi and Katsanis, 2016; Shaheen et al., 2017; Marguet et al., 2021).