A recombinase-activated ribozyme to knock down endogenous gene expression in zebrafish

Author summary Understanding mRNA and protein function requires tools to module gene expression. Current tools in vertebrates include site-directed recombinases and endonucleases, which display variable efficiency depending on the genomic context. Here, we introduce a complementary tool to knock down gene expression in zebrafish, one based on the T3H48 self-cleaving ribozyme. We first show that the T3H48 ribozyme can reduce the expression of a reporter transgene, as well as that of an endogenous gene. Using a base-editing strategy to inactivate the ribozyme, we show that this knock down is specific and reversible. We then created a Flippase- and Cre-activatable T3H48 ribozyme called RiboFlip. We find that the induction of RiboFlip recapitulates the mutant phenotype when inserted in the albino gene. Moreover, we show that a Cre- and Dre-controllable Gal4/UAS reporter in the RiboFlip cassette can label knocked-down cells independently of the expression of the target gene. Altogether, these data show that the RiboFlip can serve as a flexible knockdown tool, thereby complementing existing strategies to control gene expression.