CRISPR/Cas9-Mediated Gene Editing of the APOE4 Allele in Human Induced Pluripotent Stem Cell-Derived Neurons Reduces Amyloid-Beta Production and Tau Hyperphosphorylation

Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by progressive cognitive decline, with the apolipoprotein E4 (APOE4) allele representing the strongest genetic risk factor. APOE4 contributes to AD pathogenesis by impairing amyloid-beta (Aβ) clearance and promoting tau hyperphosphorylation and aggregation. Current therapeutic strategies are largely symptomatic and lack disease-modifying capabilities. This study investigated the potential of CRISPR/Cas9-mediated gene editing to correct the APOE4 allele to the neuroprotective APOE3 allele in human induced pluripotent stem cell (iPSC)-derived neurons. We demonstrate that precise genomic editing successfully converted APOE4 to APOE3 in these neuronal models. Subsequent biochemical analyses revealed a significant reduction in both intracellular and secreted Aβ40 and Aβ42 levels in the APOE3-edited neurons compared to their unedited APOE4 counterparts. Furthermore, we observed a substantial decrease in the phosphorylation of tau at key AD-relevant epitopes (e.g., Ser202/Thr205, Ser396/Ser404), indicative of reduced tau hyperphosphorylation. These findings suggest that direct genetic correction of the APOE4 allele via CRISPR/Cas9 technology offers a promising therapeutic avenue for mitigating core pathological hallmarks of AD, paving the way for targeted gene therapy approaches.