Accumulation of abnormally-folded tau protein and amyloid plaque formation are typical features of AD [2, 3], while accumulation of α-synuclein protein triggers death of dopamine-generating cells in the substantia nigra of PD patients [4], and intracellular aggregates of Huntingtin (Htt) protein causes HD [5]. The gene discussed is HTT; the disease is Parkinson disease.