Aristaless Related Homeobox mutations can lead to severe neurological diseases, including X-linked intellectual disability, epilepsy, as well as structural brain malformations (Table 3; Friocourt and Parnavelas, 2010), and these mutations have been studied extensively using mouse models (Kitamura et al., 2002, 2009; Marsh et al., 2009; Price et al., 2009). Here, ARX is linked to nervous system disorder.