Establishment of a tracing technique for transplanted bluefin tuna germ cells in recipient’s gonads using monoclonal antibodies specifically recognizing bluefin tuna spermatogenic cells

Our ultimate aim is to establish a small-bodied surrogate broodstock (e.g., mackerel) that produces functional gametes of the Pacific bluefin tuna Thunnus orientalis using xenogeneic germ cell transplantation. To accomplish this goal, we need to be able to sequentially trace transplanted donor cells in recipients. Here we succeeded in identifying two monoclonal antibodies that could specifically recognize the germ cells of bluefin tuna but not of the chub mackerel Scomber japonicus or the eastern little tuna Euthynnus affinis , which are promising recipient species. Using these antibodies, we developed a method to detect transplanted bluefin tuna germ cells in the gonads of xenogenic recipients. Since all stages of testicular germ cells can be recognized by these antibodies, donor germ cells can be observed throughout gametogenesis in the recipient’s gonads. Thus, the antibodies established in this study could be a powerful tool to observe survival, proliferation, and differentiation of the transplanted bluefin tuna germ cells in the gonads of small Scombridae recipients, and evaluate transplantation efficiency.