The two subjects with the mutations in the coding region had family members with mental retardation, which suggests that the novel frame shift mutation and the missense mutation at coding region of ATRX gene are involved in ATRX syndrome.
Detailed comparison of the clinical characteristics and the function of the genes located in the commonly duplicated regions of these patients led us to the hypothesis that an increased dosage of ATRX and perhaps of other genes is involved in the pathogenetic mechanism of this XLMR phenotype, including mental retardation, short stature, and genital abnormalities comprising cryptorchidism and/or a small penis.
Mutations in the X-encoded gene ATRX are known to give rise to syndromic mental retardation in male patients whereas female carriers show preferential inactivation of the mutated X chromosome and appear healthy.
These findings suggest that mutations in ATRX may cause mental retardation in females, if the X chromosome carrying mutated ATRX is not properly inactivated.
Mutations in the XNP gene have been reported in alpha thalassemia/mental retardation (MR) syndrome (ATR-X) and other severe X-linked MR conditions with facial dysmorphisms.
Given that molecular investigation of XNP/ATR-X mutations is made onerous by the length of the gene transcript, we carried out a prenatal diagnosis in a fetus at risk for ATR-X syndrome by initially determining the XNP/ATR-X gene haplotype before considering gene sequencing.
Since the identification of the ATRX gene (synonyms XNP, XH2) in 1995, it has been shown to be the disease gene for numerous forms of syndromal X-linked mental retardation [X-linked alpha thalassemia/mental retardation (ATR-X) syndrome, Carpenter syndrome, Juberg-Marsidi syndrome, Smith-Fineman-Myers syndrome, X-linked mental retardation with spastic paraplegia].
It was shown recently that mutations of the ATRX gene give rise to a severe, X-linked form of syndromal mental retardation associated with alpha thalassaemia (ATR-X syndrome).