Highly efficient and precise base editing by engineered dCas9-guide tRNA adenosine deaminase in rats

Rats are reference laboratory animal models for understanding mechanism of human diseases such as diabetes, hypertension, and neurological disorder 1 , 2 . CRISPR/Cas9 system has proved an efficient and flexible tool to generate gene modified rats 3 , 4 , 5 , 6 . Great efforts have been made to reduce the side effects and extend the application of this system 7 , 8 , 9 , 10 . Cytosine base editor (CBE), containing the engineered cytosine deaminase with CRISPR/Cas9 can be used to modify mammal genomic DNA without induction of double-strand DNA break or template. CBE targets sequence by inducing C·G to T·A conversion with a window of approximately five nucleotides 11 . Recently, the same group developed a new dCas9-guide tRNA adenosine deaminase which was capable of inducing A·T to G·C conversion. Together with CBE, ABE enables introduction of all four nucleotides transitions (C to T, A to G, T to C, and G to A) in target genomic sequence 12 . These base-editing tools provide a much safer approach compared with wild-type CRISPR/Cas9 system for gene correction of human disease. Here we report the application of this newly developed adenine base editors in rat base editing.