MAPT and Huntington disease: The main research areas of neurodegenerative diseases include: (1) tau protein disease—Alzheimer’s disease (AD); (2) extrapyramidal disorder: Parkinson’s disease (PD), Huntington’s disease (HD); (3) spinocerebellar degeneration: multiple system atrophy (MSA); (4) autonomic disorders: Shy-Drager syndrome (SDS); and (5) motor neuron disorders: amyotrophic lateral sclerosis (ALS), Werdnig–Hoffmann disease.