An Hipsc‐based Genetic Screening System to Model Aggregation of Tau Protein Allows the Identification and Validation of Possible Targets for Alzheimer’s Disease Therapies

AbstractBackgroundOne of the hallmarks of Alzheimer's Disease (AD), as with some other neurodegenerative diseases, is the misfolding and aggregation of proteins, such as amyloid‐beta and tau. Tau pathology is also believed to propagate trans‐synaptically from neuron to neuron. Either prevention of propagation, or the removal of aggregated tau, is a potential approach for AD modification.MethodDeubiquitinating enzymes (DUBs) maintain ubiquitin homeostasis by removing ubiquitin modifications from target proteins, thereby altering protein function, stability, and signaling. We hypothesize that the modulation of the ubiquitin‐proteasome system with DUB inhibitors will lead to decreased tau aggregation either directly (by inhibiting the removal of ubiquitin from tau thereby increasing its degradation) or indirectly (via modulation of other relevant pathways, like autophagy). To select relevant DUBs, we developed a phenotypic assay to assess the effect of knocking down ∼100 DUBs on the clearance of tau aggregates in hiPSC – derived neurons, assayed using high content image analysis.ResultWe show that addition of recombinant tau seeds to hiPSC – derived cortical neurons expressing a fluorescent tau reporter construct, leads to formation of tau aggregates, which we can robustly and reproducibly reduce by knocking down specific DUBs.ConclusionThe DUB enzymes revealed in our phenotypic screen have been validated in confirmatory studies and have the potential to become novel targets for the treatment of AD. In collaboration with Mission Therapeutics we will develop selective, potent DUB inhibitors for preclinical target validation.