A CRISPR–dCas Toolbox for Genetic Engineering and Synthetic Biology

Programmable control of gene expression is essential to understanding gene function, engineering cellular behaviors, and developing therapeutics. Beyond the gene editing applications enabled by the nuclease CRISPR-Cas9 and CRISPR-Cas12a, the invention of the nuclease-dead Cas molecules (dCas9 and dCas12a) offers a platform for the precise control of genome function without gene editing. Diverse dCas tools have been developed, which constitute a comprehensive toolbox that allows for interrogation of gene function and modulation of the cellular behaviors. This review summarizes current applications of the dCas tools for transcription regulation, epigenetic engineering, genome imaging, genetic screens, and chromatin immunoprecipitation. We also highlight the advantages and existing challenges of the current dCas tools in genetic engineering and synthetic biology, and provide perspectives on future directions and applications.