[Show abstract][Hide abstract] ABSTRACT: The OPHN1 gene encodes a Rho-GTPase activating protein (RhoGAP), and mutations in OPHN1 are responsible for non-specific X-linked mental retardation (NSMR). A SNP located in the 5'-untranslated region (UTRs) of OPHN1 (rs492933) was examined by PCR-RFLP to assess its contribution to cognitive ability in 234 unrelated healthy and MR children in the Qinba Mountain region in Shaanxi. The allelic frequencies of rs492933 were 0.826 for the C allele and 0.174 for the T allele. Genotype frequencies and allelic frequencies were not significantly different between the MR and the controls, or between the borderline group and the controls. In conclusion, there is no association between the OPHN1 gene polymorphism and NSMR in the Qinba Mountain region children.