A novel missense mutation in ATRX uncovered in a Yemeni family leads to alpha-thalassemia/mental retardation syndrome without alpha-thalassemia.

BACKGROUND

Intellectual disability (ID) features in numerous heritable medical conditions that result from ATRX mutations. Alpha-thalassemia mental retardation syndrome (ATR-X syndrome) is the most notable manifestation of ATRX dysfunction. In addition to ID, genitourinary and craniofacial abnormalities are regularly observed with or without alpha-thalassemia.

AIMS

The study sought to characterize two cases of ATR-X in a Yemeni family clinically and molecularly.

METHODS

PCR amplification and Sanger sequencing were used to study the ATRX gene in a Yemeni family. Also, methylation-sensitive PCR was used to perform X-inactivation studies. CADD, SNAP2 and PolyPhen-2 helped to predict the functional consequences of the variant.

RESULTS

Molecular testing revealed a novel hemizygous missense mutation (c.5666T>G) in the ATRX gene in the two Yemeni brothers. This mutation was found in a heterozygous state in the mother, with the chromosome harboring the mutated allele being under strongly skewed X-inactivation.

CONCLUSIONS

The mutated gene is predicted to have a disrupted SNF-2 domain at a conserved residue; p.Leu1889Trp, which is deemed functionally damaging. This report offers, for the first time, full clinical and molecular characterization of a novel ATRX variant in an Arab family.