The recent development of a rodent model of PD based on targeted overexpression of human α-synuclein using intra-nigral injection of an adeno-associated viral vector (AAV) has opened the possibility to investigate in more detail the graft effects in the host (as opposed to the host on the graft) and have done so by conducting side-by-side comparative studies with the standard 6-OHDA-induced rat model of PD. The gene discussed is SNCA; the disease is Parkinson disease.