Articles were selected based on searches of PubMed using a number of different search terms, such as “Neurodegenerative diseases” “Huntington's disease,” “Amyotrophic Lateral Sclerosis,” “neuroprotection,” “neurodegeneration,” “pathogenesis,” “mitochondria,” “apoptosis,” “huntingtin,” and “autophagy.” Only full-text papers written in English and its references were selected. The gene discussed is HTT; the disease is Huntington disease.