MN1 and Intellectual disability: While the function of the MN1 C-terminus remains unknown, mutations affecting this region are causative of a human congenital syndrome, “MN1 C-terminal truncation syndrome” (MCTT), manifested by neurodevelopmental disorders resulting in intellectual disability, brain abnormalities, and distinctive facial features (midface hypoplasia, cleft palate, and other skeletal anomalies) (24, 53, 54).