The subsequent identification of families with multiplication (duplication or triplication) of its allele (PARK4 locus) strengthen the link between α-syn and PD (Singleton et al., 2003; Chartier-Harlin et al., 2004), suggesting that increased expression levels of the normal α-syn can be causal for PD and others synucleinopathies. The gene discussed is SNCA; the disease is Parkinson disease.