SNCA and Parkinson disease: Previous studies have implicated some disease-related genetic alleles to the onset of PD, such as SNCA, LRRK2 (PARK8) and VPS35 (PARK17) associated with the autosomal-dominant forms of PD, or parkin (PARK-2), PINK1 (PARK6), DJ-1 (PARK7), and ATP13A2 (PARK9) that cause autosomal-recessive PD [4,5].