The finding of neuronal α-synuclein inclusions in embryonic neural grafts 11–16 years after transplantation [57, 58] in patients, raised the possibility that aggregated α-synuclein from the host PD brain may have passed into the grafted cells, and templated the conversion of soluble α-synuclein similar to infectious cases of human prion diseases. This evidence concerns the gene SNCA and Parkinson disease.