Safety Evaluation Of MSTN Gene-edited Pigs

Myostatin(MSTN)is a member of the transforming growth factor beta(TGFβ)family,also known as the growth/differentiation factor(GDF-8),which is a negative regulator of muscle growth that has an important influence on the lean meat traits of livestock and poultry.Genome-editing is a genomic point-fixed modification technique mediated by artificial nucleases,which is a kind of the important methods of gene modification technology.Nowadays,researchers all around the world used various gene editing tools to produce a variety of transgenic animal like pigs,cattle,sheep and mice.With the genome editing technology and its products gradually entering the stage of industrial application,their products will have an impact on the national economy,countries around the world have enacted laws and regulations on new gene editing techniques and their products.Chinese government attaches great importance to the safety management of genetically modified organisms and the staged management of genetically modified animals,plants and microorganisms is carried out in stages.In this study,the MSTN gene editing meishan pig made by our laboratory with using TALEN technique were chosen as experimental pigs,the wild Meishan pigs were chosen as control pigs to evaluate the safety of MSTN gene editing pigs systematically from the aspects of genetic stability of target traits,safety of gene modification technology,phenotype of ketone body traits,gene drift phenomenon and changes of intestinal microflora.The experimental results showed MSIN gene editing Meishan pigs were genetically stable and pigs body shape were healthy and normal in appearance.No significant lesions were found in any of the solid organs.The expression of MSTN gene in MSTN gene editing pigs.were reduced,the transcript analysis showed that the deletion of 2 nucleotides of the MSTN gene resulted in the formation of a stop codon in advance.and the transcription level were increased,while the MSTN protein secretion of mature body decreased.There was no significant change in blood physiology and biochemical indexes with MSTN gene editing at different stages of development.Slaughter performance results showed that the lean meat percentage and the area of the eye muscles were increased,the fat content were decreased along with the muscle quality remains unchanged.The TALEN vector used for gene editing had no off-target effect,and no random integration of FOKI gene were found.The gene drift was detected by DNA extracted from blood and intestinal microbes as well as soil microorganisms in the environment.The results showed that there were no gene drifts between gene-edited sows and wild-type piglets,gene-edited piglets and wild-type sows,gene-edited piglets and the wild-type piglets,and the edited MSTN genes did not drift to the environment either.This study preliminarily showed that MSTN gene editing Meishan pig prepared by TALEN technology has good biosafety and can be used for the next environmental release test.