CDKN1A protects medium spiny neurons from Huntington's disease pathology

Huntington's disease (HD) arises from abnormal expansion of CAG trinucleotide repeats within the HTT gene, leading to mutant huntingtin (mHTT) aggregation, progressive loss of striatal medium spiny neurons (MSNs), and progressive neurodegeneration. While the genetic cause is established, the mechanisms that confer selective MSN vulnerability, particularly those linked to aging, remain unclear. We employed a combination of miR-9/9*-124-driven reprogramming and MSN-specific transcription factors to generate patient-derived MSNs from fibroblasts of symptomatic HD patients (HD-MSNs), pre-symptomatic mutation carriers (pre-HD-MSNs), and healthy controls, preserving donor age signatures. Multi-omics analysis integrating RNA-seq and ATAC-seq revealed reduced CDKN1A expression and promoter accessibility in HD-MSNs compared with pre-HD-MSNs. Overexpression of CDKN1A in HD-MSNs alleviated HD pathologies, including DNA double-strand breaks, oxidative DNA damage, and mHTT aggregates, while improving neuronal survival and autophagy-associated activity. Conversely, knockdown of CDKN1A in pre-HD-MSNs elicited opposite effects, revealing a CDKN1A-dependent survival mechanism in HD. Together, these findings suggest that reduced CDKN1A expression may contribute to HD-associated MSN vulnerability and is associated with altered DNA damage responses and autophagy-related processes in HD-MSNs. Our study identifies CDKN1A as a potential modulator of neuronal resilience in HD.