IGF1R and microcephaly: In fact, microcephaly and mental retardation have been observed in the patients suffering from mutations in IGF1 or IGF1R.122, 123 The mutation of ADP‐ribosylation factor‐like protein 13B, a causative gene of Joubert syndrome, which is accompanied by autism,124, 125 disrupts the localization of IGF1R in primary cilia of radial glial cells and impairs the migration and placement of interneurons in the developing cerebral cortex.126, 127