OBJECTIVETo identify potential mutation in a Chinese family featuring X-linked alpha thalassemia/mental retardation syndrome (ATR-X).

METHODSBased on clinical symptoms and inheritance pattern, linkage analysis of X chromosome short tandem repeats (X-STR) loci was carried out to locate the candidate gene. Subsequently, sequences of exons and exon-intron boundaries of the candidate gene were amplified with polymerase chain reaction (PCR). Potential mutations were detected by direct DNA sequencing. All patients were also analyzed for the trait of thalassemia.

RESULTSLinkage analysis indicated the candidate gene to be ATRX. Subsequently, a homozygous missense mutation c.736C>T (p.R246C) was found in exon 9 of ATRX in all of the 3 patients. And a heterozygous mutation c.736C>T (p.R246C) was also identified in the patient's mother and grandmother. Similar mutations were not detected in other members of the family. Alpha thalassemia was detected in the proband and another patient, whose genotypes were determined as -α(3.7)/αα and --(sea)/αα, respectively.

CONCLUSIONMissense mutation of c.736C>T in ATRX gene is a mutation hotspot, and p.R246C may disturb the function of ATRX-DNMT3-DNMT3L domain (ADD), which may be responsible for the disease in this family.