Genetic engineering can expand the utility of pigs for modeling human diseases, and for developing advanced therapeutic approaches. However, the inefficient production of transgenic pigs represents a technological bottleneck. Here, we assessed the hyperactive Sleeping Beauty (SB100X) transposon system for enzyme-catalyzed transgene integration into the embryonic porcine genome. The components of the transposon vector system were microinjected as circular plasmids into the cytoplasm of porcine zygotes, resulting in high frequencies of transgenic fetuses and piglets. The transgenic animals showed normal development and persistent reporter gene expression for >12 months. Molecular hallmarks of transposition were confirmed by analysis of 25 genomic insertion sites. We demonstrate germ-line transmission, segregation of individual transposons, and continued, copy number-dependent transgene expression in F1-offspring. In addition, we demonstrate target-selected gene insertion into transposon-tagged genomic loci by Cre-loxP-based cassette exchange in somatic cells followed by nuclear transfer. Transposase-catalyzed transgenesis in a large mammalian species expands the arsenal of transgenic technologies for use in domestic animals and will facilitate the development of large animal models for human diseases.

Induced pluripotent stem cells (iPSCs) are a seminal breakthrough in stem cell research and are promising tools for advanced regenerative therapies in humans and reproductive biotechnology in farm animals. iPSCs are particularly valuable in species in which authentic embryonic stem cell (ESC) lines are yet not available. Here, we describe a nonviral method for the derivation of bovine iPSCs employing Sleeping Beauty (SB) and piggyBac (PB) transposon systems encoding different combinations of reprogramming factors, each separated by self-cleaving peptide sequences and driven by the chimeric CAGGS promoter. One bovine iPSC line (biPS-1) generated by a PB vector containing six reprogramming genes was analyzed in detail, including morphology, alkaline phosphatase expression, and typical hallmarks of pluripotency, such as expression of pluripotency markers and formation of mature teratomas in immunodeficient mice. Moreover, the biPS-1 line allowed a second round of SB transposon-mediated gene transfer. These results are promising for derivation of germ linecompetent bovine iPSCs and will facilitate genetic modification of the bovine genome.

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We describe a protocol for high-efficiency germline transgenesis and sustained transgene expression in two important biomedical models, the mouse and the rat, using the Sleeping Beauty transposon system. The procedure is based on co-injection of synthetic mRNA encoding the SB100X hyperactive transposase together with circular plasmid DNA carrying a transgene construct flanked by binding sites for the transposase, into the pronuclei of fertilized oocytes. Upon translation of the transposase mRNA, enzyme-mediated excision of the transgene cassettes from the injected plasmids followed by permanent genomic insertion produces stable transgenic animals.Generation of a germline-transgenic founder animal by using this protocol takes approximately three months. Transposon-mediated transgenesis compares favorably in terms of both efficiency and reliable transgene expression to classic pronuclear microinjection, and offers comparable efficacies to lentiviral approaches, without limitations on vector design, issues of transgene silencing, and the toxicity and biosafety concerns of working with viral vectors. Transpositionmediated gene delivery can easily be implemented by any laboratory, thereby providing an attractive method to genetically modify animals for biomedical and biotechnological purposes.

2The pig has emerged as an important large animal model in biomedical and pharmaceutical research.We describe a protocol for high-efficiency germline transgenesis and sustained transgene expression in pigs by using the Sleeping Beauty transposon system. The protocol is based on co-injection of a plasmid encoding the SB100X hyperactive transposase together with a second plasmid carrying a transgene flanked by binding sites for the transposase, into the cytoplasm of porcine zygotes. The transposase mediates excision of the transgene cassette from the plasmid vector and its permanent insertion into the genome to produce stable transgenic animals. This method compares favorably in terms of both efficiency and reliable transgene expression to classic pronuclear microinjection or somatic cell nuclear transfer, and offers comparable efficacies to lentiviral approaches, without limitations on vector design, issues of transgene silencing as well as the toxicity and biosafety concerns of working with viral vectors. Microinjection of the vectors into zygotes and transfer of the embryos to recipient animals can be performed in one day; generation of germline-transgenic lines by using this protocol takes approximately one year.