Dual-mismatch crRNA enables high-fidelity CRISPR SNV detection and equipment-free POCT
Investigators engineered CRISPR/Cas12a crRNAs with dual mismatches to overcome single-nucleotide variant discrimination limits and enable one-step isothermal detection directly from double-stranded DNA. The resulting FOCUS platform achieved attomolar sensitivity and delivered results in under 20 minutes, accurately distinguishing the SMN1 and SMN2 genes for spinal muscular atrophy genotyping. When adapted to a lateral flow strip format requiring no specialized equipment, FOCUS demonstrated 100% concordance with reference methods across 175 clinical samples spanning SMA, high-risk HPV, Staphylococcus aureus, and SARS-CoV-2. This engineering strategy provides a generalizable, low-cost pathway for field-deployable precision genotyping and point-of-care molecular diagnostics.
The original study
FOCUS: A Dual-Mismatch crRNA Strategy Unlocks High-Fidelity One-Step SNV Detection with Cas12a.
- Authors
- Zhou M, Du K, Jiang M, Xu X, Su X, Xie Y, et al.
- Journal
- ACS sensors
- Type
- Journal Article
- PMID
- 42571623
Original abstract
CRISPR/Cas12a has emerged as a powerful tool for nucleic acid detection; however, its clinical utility is severely hampered by intrinsic limitations in single-nucleotide variant (SNV) discrimination, reliance on pre-processed single-stranded DNA (ssDNA) templates, and cumbersome multi-step workflows. Here, we report a novel molecular design principle by engineering crRNAs with site-specific dual mismatches (positions 12 and 14 relative to the PAM), which we systematically demonstrate to drastically enhance the SNV discrimination capability of Cas12a. Leveraging this breakthrough, we developed FOCUS (Fast One-step CRISPR-based Universalizable SNV detection system), an all-in-one CRISPR sensing platform that enables isothermal detection of SNVs from double-stranded DNA (dsDNA) by integrating amplification and detection in a single reaction system. FOCUS achieved attomolar-level sensitivity (13.15 aM) and ultrafast readout (< 20 min) for distinguishing the highly homologous survival motor neuron 1 (SMN1) and SMN2 genes-the gold standard challenge for SNV genotyping in spinal muscular atrophy (SMA) diagnostics. To validate its clinical translatability, FOCUS was successfully adapted to a low-cost, equipment-free assay using lateral flow strips and UV visualization, facilitating point-of-care testing (POCT). In a comprehensive validation across 175 clinical samples, FOCUS exhibited 100% diagnostic concordance with gold-standard methods for SMA (21 samples), high-risk HPV 16/18 (27 samples), Staphylococcus aureus (20 samples), and SARS-CoV-2 (107 samples). Collectively, our study establishes a generalizable engineering strategy for Cas12a crRNAs and presents FOCUS as a robust, versatile, and field-deployable solution for precision SNV genotyping, underscoring the translational medicine value of FOCUS in molecular diagnostics.