APOE‐targeted epigenome therapy for late onset Alzheimer’s disease

AbstractBackgroundCarrying the APOEe4 variant significantly increases lifetime risk for LOAD. The accumulating evidence suggest that alteration of the expression of APOEe4 and APOE may hold promise as a potential therapeutics target for LOAD. In this study we developed an epigenome therapy platform to reduce APOE and APOEe4 specifically by targeted modification of the epigenome landscape within APOE locus.MethodOur approach is based on CRISPR/dCas9‐editing strategy. The novel system based on the novel bipartite repressor platform, recently developed in the laboratory. We designed targeting of APOEe4 in the allele‐discriminatory fashion, as such the editing is allele specific and precise. Furthermore, we developed a similar approach to target the regulatory elements within APOE promoter. We evaluated our platform in vitro using human hiPSC‐derived neurons and organoids, as well as in vivo by stereotactic injection of the developed system into the hippocampus of the ApoE‐humanized mice, harboring human ApoE loci replaced the mouse ortholog.ResultUsing the system, we demonstrated an efficient and precise editing of APOeE4 and APOE expressions in the hiPSC‐derived neurons and the human isogenic APOEe4 organoids. We showed that the system can robustly reduce the levels of APOE‐mRNA and the protein in both models. Importantly, the allele‐discrimination approach has resulted in no detectable editing of the e3 allele in the isogeneic hiPSC‐derived neurons, and organoids homozygous for the e3 allele. Moving onto in vivo studies, the promoter‐targeted approach using adeno‐associated‐ dCas9‐KRAB‐MeCP2 vector injected into the hippocampus of APOEe4 and APOEe3 mice, showed 50‐70% decrease in the mRNA and the protein levels. Similar effect was observed using lentivirus‐ CRISPR/Cas system targeted ApoEe4 in allele‐specific manner. Collectively, our results provided in vitro and in vivo proof‐of‐concept for the utility and efficacy of the APOE‐targeted epigenome therapy.ConclusionOur 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.