A versatile type VI CRISPR-based approach for targeted m6A demethylation in mRNAs.

Epitranscriptomics, a rapidly evolving field mainly driven by massive parallel sequencing technologies, explores post-transcriptional RNA modifications. N 6-methyladenosine (m6A) has emerged as the most prominent and dynamically regulated modification in human mRNAs, being implicated in the regulation of diverse biological processes, including spermatogenesis, heat shock response, ultraviolet-induced DNA damage response and maternal mRNA clearance. Despite the recognized significance of m6A in mRNA regulation, limited studies have focused on the targeted and efficient manipulation of this modification in mRNAs. Here, we present Dem6A-Vec, an "all-in-one" plasmid vector designed for site-specific m6A demethylation in human mRNAs. Dem6A-Vec integrates the expression of a catalytically inactive RfxCas13d fused to the m6A demethylase ALKBH5 and a U6-driven customizable guide RNA in a single construct, simplifying experimental workflows and enhancing targeting efficiency. Using nanopore direct RNA sequencing, we identify high-confident m6A sites in HeLa cells, which serve as targets for Dem6A-Vec. We validate the targeted demethylation of m6A sites in the EEF2 and RRAGA genes using the established SELECT-qPCR method, confirming the impacts on mRNA stability and highlighting the tool's precision and versatility. The presented approach is implemented in multiple mRNA sites with diverse methylation stoichiometries, underscoring its adaptability to various transcriptomic contexts. This study provides a robust and scalable method for investigating the functional roles of m6A modifications, offering a transformative platform for advancing epitranscriptomic research and potential therapeutic applications.