CHAMP1 and microcephaly: CHAMP1 functions in the regulation of kinetochore–microtubule attachment,11 and defective chromosome segregation and multipolar spindle formation were seen in lymphoblast cells isolated from an individual with a CHAMP1 mutation.12 It is known that genes related to spindle formation and chromosome segregation are mutated in severe ID and/or microcephaly, causing cortical development failure.55 Therefore, mitotic defects caused by CHAMP1 deficiency may lead to delay in mitotic progression and neuronal development.