Screening for FMR1 Expanded Alleles in Patients with Parkinsonism in Mainland China

Expanded alleles of the fragile X mental retardation 1 (FMR1) gene are generally divided into four classes based on the abundance of unstable CGG repeat expansions (CGGs) in its 5'-untranslated region. It has recently been reported that two of the four classes, premutation (55-200 CGGs) and gray zone (GZ, 40-54 CGGs) alleles, was potentially associated with parkinsonism. To investigate this association in patients in mainland China, a total of 360 Chinese patients with parkinsonism and 295 gender and age matched controls were recruited in this study. Indeed, no premutation or full mutation alleles (>200 CGGs) was detected among all the subjects. A total of 11 patients with parkinsonism were identified to have GZ alleles compared with only 1 carrier among the controls (P<0.05). Notably, 10 of the 11 GZ alleles carriers with parkinsonism were female, which was 6.8% of all 147 female patients compared with none in the control females (P<0.05). No significant difference was detected between the male groups of patients and controls. Therefore, our results indicate that FMR1 GZ allele is potentially associated with parkinsonism in mainland China, and the association is only present in the female patients, but not in the male.