Objective: To investigate the association between a new polymorphism (IVS3-20 T>C GenBank accession number: AY463003) in intro 3 of the parkin gene and the risk for Parkinson's disease (PD) in Chinese, particularly the relation between this polymorphism and the age of onset of PD patients.
Methods: PD was diagnosed according to the criteria of Core Assessment Program for Intracerebral Transplantations(CAPIT). All patients and controls were examined by two neurologists and were of the Han ethnic background. Polymerase chain reaction (PCR), denaturing high performance liquid chromatography (DHPLC) and sequencing were used to determine the genotype of each subject.
Results: A total of 312 PD patients (including 99 early-onset PD patients and 213 late-onset PD patients) and 236 controls were studied. The C/C homozygote was not found in this study. Chi-square analysis revealed that the frequencies of the C allele and T/C genotype were higher in total PD group but were not statistically different from those of the control group (P=0.6350 and 0.6331, respectively). After being stratified by age of onset, the frequency of T/C genotype was significantly higher (OR=3.52, 95%CI 0.97-13.13) in PD group with an onset age at or below 45 years old (7.07%), compared with that in the control group (2.12%). Similarly, C allele was much higher (OR=3.42, 95%CI 0.96-12.57, P=0.0276) in the early-onset PD group (3.90%) than that in the control group (1.06%). The linear trend analysis showed that both the T/C genotype and C allele increased significantly in the PD group with the increase of the onset age [chi-square(trend of Genotypes)=4.414, P=0.036; chi-square(trend of Alleles)=4.344, P=0.037]. On the other hand, there was no difference in the frequencies of allele and genotype between the late-onset PD patients and controls.
Conclusion: The above results suggest that the parkin IVS3-20 T>C polymorphism might be a genetic risk factor for early-onset PD in Chinese.