dCasRx is a catalytically inactive derivative of the naturally occurring type VI-D CRISPR ribonuclease encoded by the Ruminococcus flavefaciens XPD3002 Cas13d gene; both of the HEPN domains carry mutations, these are R239A, H244A for HEPN-1 and R858A, H863A for HEPN-2. Due to these mutations, while dCasRx can still bind to a single-stranded target RNA in the presence of a guide RNA (gRNA) which contains a spacer sequence complementary to the target RNA, it can no longer cleave the target RNA. This property can be used to manipulate the splicing of particular isoform(s) of a gene of interest, by targeting dCasRx to the motifs that are required for alternative splicing via gRNAs that are complementary to these motifs. gRNAs that target the intronic branchpoint nucleotide, splice acceptor site, putative exonic splice enhancer and splice donor site have been shown to result in increased exon skipping, with gRNAs targeting the splice acceptor site having the most potent effect for the tested gene (PMID:29551272).