Amyloid peptide (Aβ) and tau protein are most commonly associated with Alzheimer’s disease and tauopathies, α-synuclein with synucleopathies, such as Parkinson’s disease or Lewy body dementia, tar DNA-binding protein 43 (TDP-43), FUS and dipeptide repeats with amyotrophic lateral sclerosis (ALS) and/or frontotemporal lobar degeneration (FTLD), and huntingtin (Htt) with Huntington’s disease. The gene discussed is HTT; the disease is Alzheimer disease.