Bystander cellular RNAs affected by residual guide-independent collateral RNase activity

Bystander cellular RNAs refer to the collective pool of endogenous RNA molecules that undergo unintended degradation due to the collateral activity of certain CRISPR-associated enzymes, primarily the Cas13 family. In its natural bacterial context, Cas13 acts as a defense mechanism where, upon recognizing a specific viral RNA, it activates a non-specific RNase domain to cleave any nearby RNA, often leading to host cell dormancy or death (Abudayyeh et al., 2016, Science). When adapted for eukaryotic gene editing, this 'trans-cleavage' or 'collateral' activity can result in the massive depletion of host transcripts, including ribosomal and transfer RNAs, regardless of their sequence similarity to the intended target (Tong et al., 2023, Nucleic Acids Research). Recent evidence suggests that some Cas13 variants may even exhibit residual activity in a guide-independent manner, posing a significant risk for therapeutic applications where precision is paramount (Ai et al., 2022, Nature). This phenomenon is a major safety concern for RNA-targeting therapies, as it can induce significant cellular toxicity and obscure the specific phenotypic effects of the intended gene knockdown. Consequently, current research is heavily focused on engineering high-fidelity Cas13 variants or identifying orthologs with minimal collateral activity to ensure the safety and efficacy of RNA-based medicines (Shi et al., 2023, Cell Reports).

Other names

Collateral RNA cleavageTrans-cleavage of bystander RNAsNon-specific RNA degradationCas13-induced RNA toxicityOff-target RNA degradation

Non-specific endoribonuclease cleavage of bystander RNA molecules triggered by the activation of CRISPR-Cas13 proteins upon target binding or through residual guide-independent activity (Ai et al., 2022, Nature).