Recently, Dr. Xing Chang's group (supported by NSFC grants 31370858、81671552) at Shanghai Jiaotong University / Shanghai Institutes for Biological Sciences have developed a universal approach to modulate splicing and to correct disease associated defects, Based on a CRISPRguided cytidine deaminase. This technology will advance understanding of splicing and offer new opportunities for splicing related diseases. The results was published on a prestigious academic journal Molecular Cell on October 18th. The webpage of the paper is the following https://www.cell.com/molecular-cell/fulltext/S1097-2765(18)30741-X。

Expression of eukaryotic genes requires pre-mRNA splicing, which ligates exons into mature mRNAs. Alternative splicing is the primary mechanism by which to diversify proteomes in multi-cellular organisms. Unprecedented numbers of splicing isoforms have been identified with next-generation sequencing (NGS), many of which are associated with various physiological and pathological conditions. RNA splicing is a critical mechanism by which to modify transcriptome, and its dysregulation is the underlying cause of many human diseases. It remains challenging, however, to genetically modulate a splicing event in its native context.

Chang's group demonstrate that a CRISPR-guided cytidine deaminase (i.e., targeted-AID mediated mutagenesis [TAM]) can efficiently modulate various forms of mRNA splicing. By converting invariant guanines to adenines at either 50 or 30 splice sites (SS), TAM induces exon skipping, activation of alternative SS, switching between mutually exclusive exons, or targeted intron retention. Conversely, TAM promotes downstream exon inclusion by mutating cytidines into thymines at the polypyrimidine tract. Applying this approach, they genetically restored the open reading frame and dystrophin function of a mutant DMD gene in patient-derived induced pluripotent stem cells (iPSCs). Thus, the CRISPR-guided cytidine deaminase provides a versatile genetic platform to modulate RNA splicing and to correct mutations associated with aberrant splicing in human diseases.