APBA1 and microcephaly: Mutations in the Mint1-associated CASK protein have also been found to cause neurodevelopmental disorders with similar features, including mental retardation and microcephaly with ophthalmic atrophy (40, 41, 42, 43), and the human disease–linked missense variant p.Leu209Pro in CASK linked to optic nerve hypoplasia specifically disrupts Mint1 binding without impacting other protein interactions (42).