This study challenges the idea that G2019S is detrimental for motor activity in rodents, suggesting that other factors might be involved in inducing a PD-like phenotype, such alpha-synuclein (for reviews see (Greggio et al., 2011, Taymans and Cookson, 2010) or parkin (Smith et al., 2005). This evidence concerns the gene SNCA and Parkinson disease.