C9orf72 frontotemporal dementia (FTD) and amyotrophic lateral sclerosis(ALS): using patient cells and CRISPR to reveal therapeutic approaches

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PARENT PROJECT SUMMARY/ABSTRACT A hexanucleotide (GGGGCC) repeat expansion in a single allele of C9orf72 is the most common cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS), two fatal neurodegenerative of which there is currently no cure. Since there are no effective treatments for FTD (an Alzheimer’s related dementia) and ALS, there is a critical need for novel therapeutics. Targeting C9orf72 with CRISPR/Cas9 gene editing presents a promising candidate therapy. Improving our understanding of the biology of C9orf72 will facilitate employing gene editing strategies. This work utilizes novel applications of CRISPR to specifically edit or silence the diseased allele in FTD/ALS patient-derived induced pluripotent stem cells (iPSCs). Completing these aims generates a systematic evaluation of three complementary gene editing strategies for C9-FTD/ALS: 1) bi-allelic excision within the first intron harboring the repeat expansion (Aim 1), (2) allele-specific excision of the mutant allele harboring the repeat expansion (Aim 2), (3) disruption of regulatory regions to selectively silence theC9orf72 repeat expansion (Aim 3). Furthermore, we compare the ability of the editing strategies to correct disease pathology in cell types relevant to disease–human cortical and motor neurons–made possible by the fast and robust methods we developed to generate neurons from iPSCs derived from controls and patients. Analysis of the editing outcomes in control cell lines enables us to screen for precise gene editing and evaluate un anticipated effects on normal cellular function and fitness. Our findings will not only advance our search for potential therapeutic approaches, but also inform our understanding of the biology of C9orf72 biology, including how the C9orf72 gene is regulated and the mechanisms underlying disease. This and our future studies will develop a pipeline for systematically evaluating novel editing strategies that are potentially curative for C9-FTD/ALS. My work will develop Aim 3 of the parent grant (Aim 1) and expand it further (Aim 2)