Notably, injection of aggregated α-Syn from PD and DLB patient brains causes accumulation of pathogenic α-Syn aggregates in PD-relevant brain regions such as the substantia nigra pars compacta, as well as early signs of neurodegeneration in wild-type non-human primates (macaques) and mice, even in the absence of a human SNCA transgene [131]. This evidence concerns the gene SNCA and Parkinson disease.