A CRISPR/Cas9 based strategy to manipulate the Alzheimer’s amyloid pathway

The gradual accumulation of amyloid-β (Aβ) is a neuropathologic hallmark of Alzheimer’s disease (AD); playing a key role in disease progression. Aβ is generated by the sequential cleavage of amyloid precursor protein (APP) by β- and γ-secretases, with BACE-1 (β-site APP cleaving enzyme-1) cleavage as the rate limiting step 1–3 . CRISPR/Cas9 guided gene-editing is emerging as a promising tool to edit pathogenic mutations and hinder disease progression 4,5,6 However, few studies have applied this technology to neurologic diseases 7–9 . Besides technical caveats such as low editing efficiency in brains and limited in vivo validation 7 , the canonical approach of ‘mutation-correction’ would only be applicable to the small fraction of neurodegenerative cases that are inherited (i.e. < 10% of AD, Parkinson’s, ALS); with a new strategy needed for every gene. Moreover, feasibility of CRISPR/Cas9 as a therapeutic possibility in sporadic AD has not been explored. Here we introduce a strategy to edit endogenous APP at the extreme C-terminus and reciprocally manipulate the amyloid pathway – attenuating β-cleavage and Aβ, while up-regulating neuroprotective a-cleavage. APP N-terminus, as well as compensatory APP homologues remain intact, and key physiologic parameters remain unaffected. Robust APP-editing is seen in cell lines, cultured neurons, human embryonic stem cells/iPSC-neurons, and mouse brains. Our strategy works by limiting the physical association of APP and BACE-1, and we also delineate the mechanism that abrogates APP/BACE-1 interaction in this setting. Our work offers an innovative ‘cut and silence’ gene-editing strategy that could be a new therapeutic paradigm for AD.