To date, the genetic causes of a number of MCDs have been identified, including microcephaly (e.g., MCPH1, ASPM, CPAP, CDK5RAP2, and STIL), lissencephaly (e.g., LIS1, DCX, ARX, and TUBA1A), double cortex (e.g., DCX), periventricular nodular heterotopia (e.g., ARFGEF2), and tuberous sclerosis (e.g., TSC1 and TSC2)10–12. The gene discussed is DCX; the disease is tuberous sclerosis.