An engineered, compact Cas12m variant for multiplexed gene activation in vivo.

An engineered denCas12m enables smCRISPRa to process a multi-gRNA array from one transcriptional unit, supporting up to eight crRNAs for activating six genes in mice.

• Why it matters: In vivo CRISPRa is hard because required elements often exceed AAV packaging limits, limiting coordinated multi-guide control of endogenous genes.
• What they did: The team engineered a compact nuclease-dead Cas12m (denCas12m) and used its intrinsic self-processing to generate functional guides from a multi-gRNA array in smCRISPRa, then tested in mouse models.
• The result: smCRISPRa achieved efficient synergistic activation and phenotypic rescue in mouse models of Duchenne muscular dystrophy and Scn1a haploinsufficiency, and a single all-in-one AAV vector enabled high-order multiplex activation in mice.