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A Novel Mutation of the ARX Gene in a Male With Nonsyndromic Mental Retardation

Children's Health Center, St. Joseph's Hospital and Medical Center, Barrow Neurological Institute Phoenix, Arizona.

Tamara Trachtenberg, BS

Children's Health Center, St. Joseph's Hospital and Medical Center

Vinodh Narayanan, MD

Children's Health Center, St. Joseph's Hospital and Medical Center, Barrow Neurological Institute Phoenix, Arizona, vinodh.narayanan{at}chw.edu

ARX (Aristaless-related homeobox gene) is located at Xp22. It contains 5 exons and encodes a 562—amino acid protein. The protein contains 4 polyalanine tracts, 3 of which are encoded in exon 2 and 1 in exon 4. Mutations in the ARX gene have been found in X-linked infantile spasms syndrome, Partington syndrome (mental retardation with dystonic movements of the hands), X-linked lissencephaly with abnormal genitalia, X-linked myoclonus epilepsy with spasticity and intellectual disability, and in nonsyndromic X-linked mental retardation. The most common mutation in ARX (seen in X-linked infantile spasms syndrome, Partington syndrome, and X-linked mental retardation) is a 24-bp duplication in exon 2 resulting in expansion of a polyalanine tract. Truncating mutations (deletions, frameshift, non-sense) have been found in X-linked lissencephaly with abnormal genitalia, as well as homeodomain missense mutations in X-linked myoclonus epilepsy with spasticity and intellectual disability. The authors report a novel 24-bp in-frame deletion within exon 2 of the ARX gene in a male child with X-linked mental retardation and review the spectrum of ARX mutations. This mutation results in a contraction of the second polyalanine repeat.

Key Words: ARX • X-linked mental retardation

Journal of Child Neurology, Vol. 22, No. 6, 744-748 (2007)
DOI: 10.1177/0883073807304000


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