CRISPR for tauopathy

About This Grant

PROJECT SUMMARY Dementia, including Alzheimer’s disease (AD) and frontotemporal dementia (FTD), are major contributors to mortality, morbidity, and worldwide healthcare expenditure. FTD is fatal and incurable and represents 10-20% of all dementia cases. Approximately 9% of all FTD cases are caused by MAPT mutations (FTD-tau). Given that there are no effective treatments for FTD (an Alzheimer’s-related dementia), novel therapeutic strategies are urgently needed. Targeting the MAPT gene itself by CRISPR/Cas9 genome editing may provide a curative intervention. We have established a novel dual sgRNA strategy, which can excise the mutant MAPT allele in patient-derived induced pluripotent stem cells (iPSCs). The excision preserves expression from the non-diseased allele. In Aim 1, we will maximize efficiency of our gRNA strategy by identifying sgRNA pairs that excise the MAPT transcription and translation start sites on the mutant allele with high efficiency and no side effects in patient iPSCs and post- mitotic patient-derived neurons in vitro. We will then deliver our optimized editing reagents to an FTD mouse model (PS19) via AAV PhPeB, which cross the blood brain barrier and achieve brain-wide distribution. In Aim 2 we will optimize AAV dosing and determine whether CRISPR editing can reverse pathologic hallmarks of FTD- tau or only prevent their onset. In Aim 3 we will determine how three genes embedded in MAPT affect normal and pathologic tau expression, potentially providing new therapeutic targets, and in any case a useful context for any therapy that aims to alter tau expression or the MAPT locus. With the successful completion of these studies, we will have optimized a candidate gene editing strategy that targets the MAPT mutation, and reaches the highest therapeutic efficacy in human neurons in vitro. We will also determine the therapeutic window in vivo. Our editing strategy will then be ready to pair with human-specific delivery reagents that we and others are developing as they become available. We will have additionally addressed a number of open questions in the field, including whether editing efficiencies in post-mitotic neurons differ from mitotic cells, how to deliver CRISPR/Cas9 with multiple sgRNAs widely throughout the mouse brain, whether it is possible to reverse or arrest clinical phenotypes in symptomatic mice, and the impact of embedded genes on MAPT physiologic and pathologic function. This work will inform our understanding of normal MAPT function and provide proof-of-concept and IND-enabling studies for a novel MAPT CRISPR therapeutic. Our approach is likely also applicable to sporadic FTD-tau and other tauopathies, including progressive supranuclear palsy (PSP), Alzheimer’s disease (AD) and corticobasal degeneration (CBD). Our overarching goal is to accelerate genome editing for neurodegenerative diseases toward the clinic.