Update on somatic mutations in major neurodegenerative diseases: mutational signatures in neurons and mosaicism

Somatic mutations in major neurodegenerative diseases are poorly understood, but research over the past 2 years provides valuable insights. Single-cell whole-genome sequencing of vulnerable neurons in Alzheimer's disease and amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) revealed excess accumulation of single-nucleotide variant signatures and two-bp deletions independent of pathogenic protein aggregation. Increased oxidative DNA damage and possibly impaired DNA damage repair pathways may explain more pronounced signatures in patients. Ultra-deep sequencing of disease-associated genes in relevant tissues in ALS/FTD identified a subset of sporadic patients carrying mosaic variants that cause disease when present in the germline, but the pathogenicity of such mosaic variants at low allele frequencies is unclear. Research on somatic variants in Parkinson's disease remains underrepresented in the literature.