FRAXAC1 and DXS548 polymorphisms in the Chinese population

The fragile X syndrome is the most common inherited form of mental retardat ion. Haplotype studies using FRAXAC1 and DXS548 polymorphic markers flankin g the fragile site have demonstrated linkage disequilibrium at the FMR1 loc us. We investigated the association of the FRAXAC1, DXS548 and CGG alleles between normal subjects and mentally retarded (MR) patients of unspecified cause who do have fragile X syndrome. We have evaluated the FRAXAC1 site in 390 normal subjects and 321 MR patients and the DXS548 site in 146 normal and 319 MR subjects, Both FRAXAC1 and DXS548 alleles were determined by app lication of the polymerase chain reaction. When compared with Caucasians, t he normal Chinese population has a different FRAXAC1 allele distribution. T here are more AC,, repeat alleles and fewer AC,, repeat alleles, The DXS548 allele distributions were similar between Chinese and Caucasians, The same distribution pattern of FRAXAC1 alleles was found in both normal subjects and MR patients, but there were significant differences in the distribution patterns of DXS548 alleles, The FMR1 CGG-DXS548 and FRAXAC1-DXS548 haploty pe distribution between normal subjects and MR patients also differed signi ficantly. Our results suggest a possible association between DXS548 alleles and non-FRAXA mental retardation. (C) 1999 Wiley-Liss, Inc.