APOE-Targeted Epigenome Therapy for Late Onset Alzheimer's Disease

Abstract Background There is an urgent need to refocus Alzheimer’s disease (AD) drug discovery on new targets and shifting the paradigm of AD DRUG DEVELOPMENT towards precision medicine. Apolipoprotein E gene ( APOE ) is the strongest and most reproduceable genetic risk factor for late‐onset Alzheimer’s disease (LOAD), and thus holds promise as a potential therapeutics target for LOAD. In this study we developed an epigenome therapy platform to reduce APOE expression generally and APOE e4 specifically by targeted modification of the epigenome landscape within APOE locus. Methods Our gene therapy strategy is based on CRISPR/deactivated (d)Cas9 editing technology fused with an effector molecule and delivered by lentiviral (LV) vehicle. Our gRNAs were designed to target regulatory elements in the APOE promoter and in exon 4 overlapping the SNP that define the APOE e4 allele. We evaluated our epigenome therapy platform in vitro using human hiPSC‐derived neurons and in vivo by stereotactic injection of reporter gene into the hippocampus of mice. Results The LV dCas9‐repressor vector showed decreased APOE ‐mRNA and protein overall levels in hiPSC‐derived neuronal model. To specifically target the APOE e4 allele we utilized the VRER‐dCas9 protein. Evaluation of the system specificity showed a reduction in APOE ‐mRNA levels in the hiPSC‐derived neurons with the e4 allele while there was no effect in the isogeneic hiPSC‐derived neurons homozygous for the e3 allele. Moving onto in vivo studies in mice administration of LV dCas9‐repressor vector and the GFP reporter gene into the hippocampus showed 50‐70% decrease in GFP expression demonstrating promising preliminary data. Collectively, our results provided in vitro and in vivo proof‐of‐concept for the utility and efficacy of the APOE ‐targeted epigenome therapy. Conclusions Our epigenome therapy strategy for fine‐tuning of APOE expression based on dCas9 technology is translational toward the development of a therapeutics approach to prevent and/or delay LOAD onset. Furthermore, the technology offers the opportunity to refine the platform for the development of gene‐specific and even allele‐ and cell‐type‐ specific therapies, and by that enables the advancement of strategies for precision medicine in LOAD.