Prospect of creating trans-genic animals by using sper-matogonial transplantation

Transgenic animal technology is a powerful tool for researching bioscience, biomedicine, bioreactor, and ag- riculture. There are various ways to produce transgenic animals. The most common ways currently available are pronuclear microinjection and nuclear transfer techniques. However, these methods usually result in low efficiency, causing mosaic (in pronuclear microinjection), or develop- mental abnormalities (in nuclear transfer). In 1994, Brinster and his colleagues reported an original method to transfer spermatogonial stem cells from donor to recipient mice. The donor spermatogonia were able to form spermatozoa in re- cipient testes, and to produce progeny carrying the donor’s genetic characters. Since then, a series of novel methods were invented by using spermatogonia transplantation. These new methods facilitate the research and application of sper- matogonia. Some of these methods, when combining with genetic modification methods, will form a novel methodology for creating transgenic animals. The present paper reviews the achievements of research on spermatogonia transplanta- tion related to creating transgenic animal. Such as, trans- plantation techniques, cryopreservation of spermatogonia, preparation of recipients, long-term proliferation of sper- matogonia in culture, genetic modification of spermatogonia, and characterization of germ line transmission of the modi- fied gene, etc. Furthermore the methodologies for creating transgenic animals by using spermatogonia transplantation were described. Based on the difference between donors and recipients used, the methodology is categorized into two groups: allogeneic transplantation, and autologous trans- plantation. Although progress in this research area has been swift, potential difficulties remain to be overcome in each approach. The advantages and existing problems in the methodology are discussed.