DUX4 and facioscapulohumeral muscular dystrophy: For example, Himeda et al. established a CRISPRi system with dead SaCas9 (dSaCas9) and successfully inhibited the expression of full-length DUX4 mRNA (DUX-fl) in vitro, alleviating facioscapulohumeral muscular dystrophy (FSHD).139 Double AAV vectors incorporate separately designed plasmids encoding a split Cas9 to accommodate the limited AAV carrying capacity, along with sgRNA.