Guide RNAs block reverse transcription and inflate CRISPR RNA knockdown measurements
Standard quantitative reverse transcription PCR assays consistently overestimate RNA knockdown efficiency across RNA-targeting CRISPR platforms, according to a study in Nature Biotechnology. Guide RNAs copurify during extraction and physically block reverse transcription of target transcripts, creating an artifact that affects upstream amplicons. The team tested Cas13 and Csm systems against human targets including XIST and BRCA1. They observed false knockdown signals even with catalytically inactive enzymes. The authors recommend using strand-displacing reverse transcriptases alongside other assays to confirm true transcript depletion.
RNA biologists studying transcript depletion in cells must adjust their quantification protocols to prevent false positive knockdown readouts.
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