RfxCas13d

**RfxCas13d**, also known as **CasRx**, is a compact CRISPR-Cas13d effector protein derived from Ruminococcus flavefaciens, widely used for programmable RNA knockdown in mammalian cells. It forms a complex with a CRISPR RNA (crRNA) guide to specifically bind and cleave target single-stranded RNAs via its two HEPN nuclease domains, without requiring a protospacer flanking sequence (PFS), enabling versatile targeting. Upon target engagement, it undergoes conformational changes activating both cis-cleavage of the target and trans-collateral cleavage of bystander RNAs, particularly when targeting abundant transcripts, which can lead to transcriptome-wide degradation, chromatin collapse, and cell proliferation defects. RfxCas13d has been delivered via AAV vectors to the CNS for gene silencing in models of amyotrophic lateral sclerosis (SOD1) and Huntington's disease (HTT), and applied in PAC-MAN strategies against SARS-CoV-2, with catalytically dead (dRfxCas13d) variants used for translation repression or editing fusions. Its small size facilitates viral delivery, though collateral activity requires careful optimization for therapeutic use.[1][2][5][7]

Other names

Cas13dCas-13dCas 13d