DCX and lissencephaly type 1 due to doublecortin gene mutation: Key examples include the identification of doublecortin (DCX) as the gene underpinning abnormal cerebral cortex development and morphology in patients with X-linked lissencephaly (XLS); analysis of XLS has underscored the importance of normal neuronal migration during cerebral cortex development (Allen and Walsh 1999; Gleeson et al, 1999).