CRISPR gene therapies targeting tau in Alzheimer's disease and tauopathies

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PROJECT SUMMARY / ABSTRACT The MAPT gene encoding the tau protein is an ideal target for Alzheimer’s disease (AD) therapeutics since it forms hallmark pathology in all AD patients. In mice, tau aggregation drives disease progression, while depleting tau leads to cognitive improvements, suggesting targeting tau may benefit human patients as well. A major question has been how to achieve this goal. CRISPR technology (Clustered Regularly Interspaced Short Palindromic Repeats) has blossomed in recent years, and we can now leverage this approach to specifically deplete tau in neurons. By targeting different tau isoforms with site-specific guide RNAs of interest, one can conceivably target the specific tau variants that are present in 3R-tauopathies (e.g., Pick’s disease), 4R tauopathies (e.g., corticobasal syndrome), or mixed 3R/4R tauopathies (e.g., AD patients). Thus, we turned to a newly developed CRISPR/Cas13 technology, which allows targeting and depletion of RNA transcripts rather than DNA itself, the latter of which can have unwanted effects on the genome including DNA damage and even tumorigenesis. CRISPR/Cas13 technology could provide new opportunities for therapeutic tau reduction and potentially overcome many of the limitations that have plagued tau depletion strategies. In fact, our preliminary findings show that we can computationally predict which guides will successfully target and deplete tau, and we demonstrated this in a human cell line and primary human neurons, suggesting we have found an optimal pipeline for guide prediction, development, and validation. Therefore, we have an exciting opportunity to develop an effective, non-invasive tool for tau gene therapy in the nervous system (CNS). In Aim-1, we will develop and refine the CRISPR/Cas13 system to target tau and will comprehensively identify the most optimal guide RNAs that target either 3R-tau, 4R-tau, or total tau. We will deliver those guides to neurons and determine their effectiveness and ability to restore normal neuronal function. In Aim-2, we will perform preclinical efficacy testing and determine whether our most optimal CRISPR/Cas13 complexes have therapeutic potential in AD model mice. By delivering tau-targeting guides peripherally using brain-penetrant AAV methods, we will evaluate their therapeutic impact by performing a battery of biochemical, histological, and behavioral studies at either early (preventative) or late (therapeutic) stages of disease progression. This study is innovative and significant since it will both develop the CRISPR technology needed to target tau, and also advance gene therapy approaches to deplete tau in humans including AD and other dementia patients. The clear implications are that targeting and reducing tau levels, even modestly, could provide a new treatment modality for dementia patients.