Expanding the phenotype associated with missense mutations of the ARX gene

Abstract

The Aristaless-related homeobox gene (ARX, OMIM# 300382)located in chromosome Xp21.3 belongs to a family of homeobox genes that encode transcription factors playing a crucial role during early embryogenesis. In the brain, ARX is involved in cerebral development and patterning. Mutations in ARX have been shown to cause different forms of intellectual disability, which are classified as a malformation and a nonmalformation group of phenotypes. The latter involves mainly expansions of the trinucleotide repeats coding the second and first polyalanine tracts (polyA). Only few missense mutations in ARX have been reported in nonmalformed patients to date [Shoubridge et al., 2010; Sartori et al., 2011]. Here, we report on a large family with recurrence of intellectual disability and dystonia due to a novel missense mutation in ARX. There were nine affected males over two generations and there was an X-linked pattern of inheritance (Fig. 1). Patient cognitive and social skills were assessed by means of the Wechsler Intelligence Scale for Children (WISC-R) and Edgar Doll’s Vineland Social Maturity Scale (VSMS)