This direct, systematic sequencing screen of the coding exons of the X chromosome has identified nine XLMR-associated genes, which can now be used in the provision of genetic diagnostics to families with mental retardation. Mental retardation–causing variants in these genes are predominantly in families previously classified as having nonsyndromic mental retardation, emphasizing the utility of a systematic sequencing strategy in resolving phenotypically similar sets of disease cases that are heterogeneous with respect to their underlying genetic causation.
