Targeted demethylation of cathepsin D via epigenome editing rescues pathology in Alzheimer's disease mouse model.

Cathepsin D (Ctsd) has emerged as a promising therapeutic target for Alzheimer's disease (AD) due to its role in degrading intracellular amyloid beta (Aβ). Enhancing Ctsd activity could reduce Aβ42 accumulation and restore the Aβ42/40 ratio, offering a potential AD treatment strategy. This study explored Ctsd demethylation in AD mouse models using dCas9-Tet1-mediated epigenome editing. We identified dCas9-Tet1 as an effective tool for demethylating the endogenous Ctsd gene in primary neurons and brains. Treatment with Ctsd-targeted dCas9-Tet1 in primary neurons overexpressing mutant APP (mutAPP) reduced Aβ peptide levels and the Aβ42/40 ratio. Additionally, demethylation of Ctsd via dCas9-Tet1 in 5xFAD mice significantly altered Aβ levels and alleviated cognitive and behavioral deficits. These findings offer valuable insights into developing epigenome editing-based gene therapy strategies for AD.