We next asked whether RfxCas13d could target the G4C2 repeat RNA in a mouse model of C9-ALS/FTD, specifically C9-BACexp mice56, which harbor a bacterial artificial chromosome encoding the full-length human C9ORF72 gene with ~100–1000 copies of the hexanucleotide repeat. The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.