Dogs exhibit close similarities to humans in terms of metabolic,physiological, and anatomical characteristics, and thus are ideal genetic and clinical models to study human diseases. Gene target technology is a powerful tool to create new strains of animals with favorable traits. However, thus far, gene-target dogs have not been developed due to their unique species-specific reproductive characteristics, which limits the applications of dogs especially in the field of biomedical research. Recently, clustered regularly inter-spaced short palindromic repeats (CRISPRs)/CRISPR-associated (Cas) 9 system was applied by Prof Lai liangxue’s group to edit specific genes with a high efficiency.
Beagle dog, the most widely used breed in biomedical research, was used as their animal model. Myostatin(MSTN) was chosen as the first gene of interest. MSTN is a negative regulator of skeletal muscle mass. Spontaneous mutations of MSTN cause muscle hypertrophy in many species, including dogs, without causing severe adverse consequences. Firstly, Prof Lai’s group designed functional and effective sgRNA in canine cells. Secondly, they generated MSTN KO dogs by manipulating dog zygotes using an auto-transplantation strategy. Eventually, 8 females were pregnant and gave birth to 27 puppies. Two puppies from different mothers were found with genetic mutations in MSTN locus.
In summary, scientists from Prof Lai’s group demonstrated for the first time that a single injection of Cas9 mRNA and sgRNA corresponding to a specific gene into zygotes, combined with an auto-embryo transfer strategy, can efficiently generate site-specific genome-modified dogs. This approach may not only greatly facilitate the generation of novel dog models for biomedical research, but also promote the creation of new strains of dogs with favorable traits for other purposes.