TY - JOUR T1 - Two therapeutic CRISPR/Cas9 gene editing approaches revert FTD/ALS cellular pathology caused by a <em>C9orf72</em> repeat expansion mutation in patient derived cells JF - bioRxiv DO - 10.1101/2022.05.21.492887 SP - 2022.05.21.492887 AU - M Sckaff AU - K Gill AU - A Sachdev AU - AM Birk AU - O Aladesuyi Arogundade AU - HL Watry AU - KC Keough AU - Y-C Tsai AU - J Ziegle AU - BR Conklin AU - CD Clelland Y1 - 2022/01/01 UR - http://biorxiv.org/content/early/2022/05/21/2022.05.21.492887.abstract N2 - CRISPR gene editing holds promise to cure or arrest genetic disease, if we can find and implement curative edits reliably, safely and effectively. Expansion of a hexanucleotide repeat in C9orf72 is the leading known genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). We evaluated three approaches to editing the mutant C9orf72 gene for their ability to correct pathology in neurons derived from patient iPSCs: excision of the repeat region, excision of the mutant allele, and excision of regulatory region exon 1A. All three approaches normalized RNA abnormalities and TDP-43 pathology, but only repeat excision and mutant allele excision completely eliminated pathologic dipeptide repeats. Our work sheds light on the complex regulation of the C9orf72 gene and suggests that because of sense and anti-sense transcription, silencing a single regulatory region may not reverse all pathology. Our work also provides a roadmap for evaluating CRISPR gene correction using patient iPSCs.Competing Interest StatementB.R.C. is a founder of Tenaya Therapeutics (https ://www.tenay ather apeut ics.com/), a company focused on finding treatments for heart failure, including genetic cardiomyopathies. B.R.C. holds equity in Tenaya. C.D.C and B.R.C. are inventors on a patent application for this work. The other authors declare no competing interests. ER -