Autistic spectrum disorders (ASD) occur more frequently in males, suggesting a major pathogenic role for genes located on the X-chromosome. The analysis of X chromosome inactivation (XCI) pattern may help to identify XCI skewing in those families in which such genes are involved, even without identifying the specific genetic mutation. In order to identify such families, we determined the XCI pattern in 40 females with ASD and 58 mothers of children with ASD, as well as in 80 matched control females. The X inactivation assay was carried out on genomic DNA extracted from peripheral blood. XCI was calculated for informative heterozygous individuals as the ratio of the peak area of two alleles of the highly polymorphic CAG repeat of the androgen receptor (AR) gene (Xq11-12). Our results indicate that there is no difference in XCI pattern both in ASD females and in the mothers of ASD patients when compared with the appropriate controls. These findings suggest that the contribution of X-linked genes to the etiology of ASD is still likely but it is not supported by X-inactivation patterns on peripheral blood cells.
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