Aggregates of mutant Huntingtin protein (htt) are detected in Huntington’s disease (HD), accumulation of tau and β-amyloid proteins is detected in Alzheimer’s disease (AD), α-synuclein positive Lewy bodies are observed in Parkinson’s disease (PD) and neurofilament accumulations are seen in amyotrophic lateral sclerosis (ALS). The gene discussed is MAPT; the disease is Parkinson disease.