Analysis of Exon Dosage Using Multiplex Ligation-Dependent Probe Amplification in Chinese Patients with Early-Onset Parkinson’s Disease

Introduction: Several studies have identified a number of genes associated with Parkinson’s disease (PD). Genomic rearrangements (exon dosage variations) in these genes have emerged as significant, causing mutations. However, exon dosage variations in several PD genes were rarely investigated in Chinese patients. Objective: This study was aimed at determining the prevalence of PD-causing genes’ exon rearrangements in Chinese sporadic early-onset PD (EOPD) patients. Methods: A total of 150 Chinese sporadic EOPD patients and 100 healthy controls were enrolled. Multiplex ligation-dependent probe amplification (MLPA) was used to detect exon dosage in PD genes, including SNCA, PARKIN, UCHL1, PINK1, DJ1, LRRK2, and ATP13A2. Positive results were verified by real-time quantitative polymerase chain reaction. And exon sequencing was employed to screen for subtle mutations. Novel exon dosage variations were screened in families and controls. Results: PARKIN exon rearrangements were detected in 10 (6.7%) patients, including a novel heterozygous duplication of PARKIN exons 1–4. Clinical investigation showed that the percentage of individuals with PARKIN exon rearrangements was higher in the younger patients. Notably, the MLPA screening detected a heterozygous deletion of UCHL1 exon 1 in a patient. MLPA analysis in the family detected the deletion in an asymptomatic sister, indicating incomplete penetrance. Conclusion: Exon copy number variations (CNVs) in the PARKIN gene are relatively common among Chinese sporadic EOPD patients, whereas exon CNVs in other known PD genes can also be detected. Our findings demonstrate that it is important to perform exon dosage analysis for several known PD genes to obtain a better mechanistic insight into PD pathogenesis.