Differences in the SNCA sequence between rodents and humans may explain some of the difficulties in modelling genetic PD, since rodents, indeed most vertebrates, encode a threonine at position 53 which is a cause of PD in humans, and human A53T mice have demonstrated exaggerated motor deficits and α-synuclein pathology following removal of endogenous mouse α-synuclein (Cabin et al., 2005). This evidence concerns the gene SNCA and Parkinson disease.