SNCA variants rs2736990 and rs356220 as risk factors for Parkinson's disease but not for amyotrophic lateral sclerosis and multiple system atrophy in a Chinese population.

Previous studies found that polymorphisms rs2736990 and rs356220 in the alpha-synuclein (SNCA) gene increase the risk for Parkinson's disease (PD) in a Caucasian population. In consideration of the overlapping of clinical manifestations and pathologic characteristics among PD, amyotrophic lateral sclerosis (ALS), and multiple system atrophy (MSA), the possible associations of these 2 polymorphisms and 3 neurodegenerative diseases were studied in the Chinese population. A total of 1011 PD, 778 sporadic ALS (SALS), 264 MSA patients, and 721 healthy controls (HCs) were studied. All subjects were genotyped for the 2 polymorphisms using polymerase chain reaction and direct sequencing. Significant differences in the genotype frequencies (p = 0.0188 and 0.0064, respectively) and minor allele frequencies (MAFs) (p = 0.0065 and 0.0095, respectively) of rs2736990 and rs356220 were observed between the PD patients and HCs. Moreover, significant differences were found between the early-onset PD patients (<50 years) and matched controls but not in the late-onset PD patients (≥50 years). However, no differences were observed between subgroups with regard to clinical features, such as sex, onset symptoms (tremor or rigidity), cognition (normal or abnormal), and anxiety and depression (presence or absence). No significant differences were found in the genotype frequencies and MAFs of these 2 single-nucleotide polymorphisms between SALS patients and HCs and between MSA patients and HCs. No significant differences were found between subgroups with regard to the clinical presentation of SALS and MSA. Our results show that rs2736990 and rs356220 in SNCA decreased the risk for PD in a Chinese population. These candidate polymorphisms were unlikely to be the causes of SALS and MSA in this population.