Multiplexed modulation of endogenous genes is crucial for sophisticated gene therapy and cell engineering. CRISPR-Cas12a systems enable versatile multiple genomic loci targeting by processing numerous crRNAs from a single transcript, however, their low efficiency has hindered applications in vivo . Through structure-guided protein engineering, we develop a hyper-efficient LbCas12a variant, termed hyperCas12a, with its catalytically dead version hyperdCas12a showing significantly enhanced efficacy for gene activation, particularly at low crRNA conditions. We demonstrate that hyperdCas12a has minimal off-target effects compared to the wildtype system and exhibits enhanced activity for gene editing and repression. Delivery of the hyperdCas12a-activator and a single crRNA array simultaneously activating endogenous Oct4, Sox2, and Klf4 genes in the retina of postnatal mice alters the differentiation of retinal progenitor cells. The hyperCas12a system offers a versatile in vivo tool for a broad range of gene modulation and gene therapy applications.

Biological signal recording enables the study of molecular inputs experienced throughout cellular history. However, current methods are limited in their ability to scale up beyond a single signal in mammalian contexts. Here, we develop an approach using a hyper-efficient dCas12a base editor for multi-signal parallel recording in human cells. We link signals of interest to expression of guide RNAs to catalyze specific nucleotide conversions as a permanent record, enabled by Cas12’s guide-processing abilities. We show this approach is plug-and-play with diverse biologically relevant inputs and extend it for more sophisticated applications, including recording of time-delimited events and history of CAR-T cells’ antigen exposure. We also demonstrate efficient recording of up to four signals in parallel on an endogenous safe-harbor locus. This work provides a versatile platform for scalable recording of signals of interest for a variety of biological applications.

CRISPR-Cas nucleases and their nuclease-deactivated dCas variants have revolutionized the field of genome editing and gene regulation. Cas12a possesses intrinsic RNAse activity and can process multiple functional crRNAs from a single long transcript, making it a powerful tool for multiplex gene targeting. We engineered a dCas12a variant termed hyperCas12a with superior efficacy in gene editing and multiplex gene regulation, especially at restrictive crRNA concentrations. Here, we describe a step-by-step protocol for constructing and validating a crRNA array, and using it with the hyperdCas12a system for multiplex gene regulation in vivo by subretinal delivery in mice.

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