C9orf72 and Parkinson disease: To determine the involvement of C9orf72 in the pathogenesis of PD, we measured the expression of C9orf72 in 3 PD models with the environmental factor 1‐methyl‐4‐phenyl‐1,2,3,6 (MPTP), genetic factor α‐synuclein A53T, and preclinical factor recombinant α‐synuclein PFF.