Extrachromosomal DNA: Molecular perspectives in aging and neurodegenerative diseases.

Extrachromosomal DNA (ecDNA) refers to a class of circular, non-chromosomal DNA that has recently gained widespread attention due to its potential role in aging and neurodegenerative diseases. The generation of ecDNA is closely associated with processes such as double-strand breaks, micronuclei formation, and the breakage-fusion-bridge (BFB) cycle, all of which are integral to regulation of gene expression, genetic stability, and clonal evolution. In neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease, the aberrant formation of ecDNA is closely linked to defects in DNA repair, alterations in synaptic plasticity, and neuronal dysfunction. The distinct distribution and functional roles of ecDNA in these conditions make it a potential diagnostic biomarker and therapeutic target. This review provides an overview of the mechanisms underlying ecDNA formation and its functions in the nervous system. Additionally, it explores the clinical potential of ecDNA in disease diagnosis, targeted therapy, and personalized medicine, offering new insights for future research and treatment strategies.