[Exploration and characterization of a universal piggyBac transposon vector for efficient transgene studies in sheep]

piggyBac (PB) is a DNA transposon that mediates transposition in various animal cells. As an efficient tool, PB transposons are applied to various transgenic research and optimized for different species, which is an essential means to enhance its versatility. To construct a universal PB transposase (PBase) vector for ovine transgene manipulation, the gene expression box of PBase with optimized bias for sheep codons was inserted into the pBNW-TP1 vector. The vector pBNW-TP2 with a single plasmid was successfully constructed. Then, pBNW-TP2 was transfected into ovine fibroblasts and mammary epithelial cells. The stable transfected cell lines were selected by G418 and the PB transposition sites were determined by Tail-PCR in the stable transfected cell lines. The transposition efficiency was verified by student's t-tests for cell clones with methylene blue staining. The results showed that pBNW-TP2 successfully guided the production of transgenic ovine fibroblasts and mammary epithelial cell lines. The PB transposition test indicated that the pBNW-TP2 vector can be specifically integrated into the TTAA sites of the sheep genome. The statistical analysis of methylene blue staining results suggested that the transgenic efficiency mediated by the pBNW-TP2 vector increased significantly. In summary, we verified and analyzed characteristics of the universal PB transposon vector pBNW-TP2 for sheep in this study, which will provide a scientific basis for future transgenic research mediated by the PB transposon in ovine somatic cells.