C9orf72 and amyotrophic lateral sclerosis: Currently, preclinical treatments for ALS/FTD caused by C9ORF72 repeat expansion are mainly focused on its abnormal RNA, including antisense oligonucleotide (ASO)-based target RNA silencing, microRNA-based silencing, dCas9-based transcription inhibition, and dCas9-based target RNA editing11,17,18,49–52.