PARENT SESSION

(MS10) GERM CELL TRANSPLANTATION AND TRANSGENESIS IN PIGS AND GOATS.

Dobrinski, Ina¹, ¹ Center for Animal Transgenesis and Germ Cell Research, Kennett Square, PA

ABSTRACT- Transplantation of genetically modified germ cells to the testis of a recipient animal can result in production of transgenic sperm and offspring and is an alternative to currently inefficient transgenic technology in domestic species. Germ cell transplantation was first reported in mice. Xenogeneic spermatogenesis in mice did not occur with germ cells from donor species other than rodents. Therefore, homologous recipient models were established in domestic animals. Due to different testicular anatomy in rodents and large animals, germ cells cannot be delivered by the same technique. Instead, ultrasound-guided cannulation of the rete testis with low pressure cell delivery was successful in pigs, goats, and subsequently cattle. A transgenic goat born after transplantation of transgenic donor cells and mating of a recipient buck to a wild-type doe carried the same transgene integration pattern as the donor, providing proof of donor-derived sperm production, fertility, and transmission of a stable genetic germ line modification. While immunological tolerance between donor and recipient is required in rodents, transplantation was successful between unrelated, immuno-competent pigs or goats. Efficiency of engraftment can be further increased by depletion of recipient germ cells and enrichment of donor cells for stem cells. Local irradiation of the testes or in utero exposure to busulfan reduces endogenous germ cell numbers without irreversibly damaging the testis environment. While cell populations enriched in stem cells have been harvested from rodents with induced cryptorchidism by flow sorting for expression of cell surface antigens, the need for larger cell numbers make enrichment based on differential adhesion of germ cells a more practicable approach in pigs and goats. Work is now directed at establishing efficient culture systems allowing selection and expansion of germ cells with stable transgene integration. Transgenic rodents have been generated by viral transduction of germ cells prior to transplantation. Use of a viral vector to introduce a transgene into porcine and caprine germ cells has also shown promising results. Development of improved in vitro systems for targeted germ cell transduction will make germ cell transplantation a viable approach to transgenesis in domestic species.

KEY WORDS: testis, transgenesis, germ cell, transplantation