Genetic analysis of the ATG7 gene promoter in sporadic Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease. The majority of PD cases are sporadic, for which genetic causes and underlying molecular mechanisms remain largely unclear. Autophagy, a highly conserved cellular process that governs the breakdown of long-lived proteins and organelles, has been involved in the degradation of α-synuclein (α-Syn), the main component of Lewy bodies. Accumulating evidence implicates deregulation of autophagy in the development and progression of sporadic PD. Altered autophagic gene expression has been observed in the brain tissues from PD patients and animal models. We hypothesized that changes in expression levels of autophagy-related genes (ATGs), rather than mutations associated with amino acid changes, may contribute to PD onset. In this study, the ATG7 gene promoter was sequenced bi-directionally in groups of sporadic PD patients and ethnic-matched healthy controls. As predicted, four novel heterozygous variants, 11313449G>A, 11313811T>C, 11313913G>A and 11314041G>A, were identified in five PD patients, but in none of the controls, which significantly decreased transcriptional activities of the ATG7 gene promoter. Two novel heterozygous variants, 11312947G>A and 11313006C>G, were only found in controls, which did not affect transcriptional activities of the ATG7 gene promoter. The other five novel variants were found in PD patients and controls with similar frequencies. Taken together, the sequence variants within the ATG7 gene promoter identified in PD patients may change ATG7 protein levels, which in turn would influence autophagic activity, contributing to PD onset as a risk factor.