SNCA and Parkinson disease: The fact that we did not observe a reversal of motor hyperactivity into frank hypokinesia, as in α-synuclein overexpressors (Lam et al., 2011), up to 19 months, might indicate a longer and slower pre-symptomatic phase in G2019S KI mice, in line with the different ages at onset of the disease, i.e. juvenile for α-synuclein related PD, and late for G2019S related PD (Hardy et al., 2009).