CRISPR/Cas12a dual-gRNA assay enables precise detection of single-nucleotide mutations via cis-staggered-cleavage

Robust discrimination of single-nucleotide mutations (SNMs) remains a central challenge in nucleic acid analysis, particularly under minimal sequence constraints. Here, we report a programmable CRISPR/Cas12a sensing strategy, termed STAND (cis-staggered-cleavage-based dual-gRNA assay), that enables precise SNM discrimination through a structurally gated cleavage cascade. In this system, a primary guide RNA directs Cas12a to perform site-specific cis-staggered cleavage of double-stranded DNA, generating a predictable sticky-end intermediate. This transient structure is subsequently recognized by a secondary guide RNA via strand displacement and branch migration, which reactivates Cas12a for PAM-independent trans-cleavage of reporter substrates. This sequential, structure-mediated activation decouples target recognition from PAM constraints and converts single-nucleotide variations into amplified fluorescence signals with high fidelity, and achieves a detection limit as low as 10¹ CFU/mL. We demonstrate that STAND achieves accurate SNM discrimination in clinically relevant targets, including the nuc gene of Staphylococcus aureus and methicillin-resistant S. aureus, outperforming conventional qPCR in specificity. Owing to its modular design, minimal guide requirements, and programmable architecture, this strategy establishes a generalizable framework for high-resolution genetic analysis and molecular diagnostics.