Targeted manipulation of mA RNA modification through CRISPR-Cas-based strategies.

N-methyladenosine (mA) is a reversible and prevalent internal modification in RNAs and can be dynamically modulated by methyltransferase and demethylase. Targeted manipulation of mA RNA modification is critical in studying the functions of specific mA sites as well as developing molecular therapies through targeting mA. The CRISPR-Cas systems including CRISPR-Cas9 and CRISPR-Cas13 have been widely used to edit and modify specific nucleotides on DNA and RNA through fusing effective proteins such as enzymes with Cas9/13. Through taking advantage of the mA methyltransferase and demethylase, a series of CRISPR-Cas-based methods have also been developed to manipulate the mA methylation at specific RNA sites. This review summarizes the latest CRISPR-Cas13 and Cas9 toolkits for mA site-specific manipulation, including fundamental components, on-target efficiency, editing window, PAM/PFS requirement, and subcellularly localized targeting as well as potential limitations. We thus aim to provide an overview to assist researchers to choose an optimal tool to manipulate mA for different purposes and also point out possible optimization strategies.