Progress and application prospect of germ cell transplantation technique in fish

Germ cell transplantation is a technique that donor germ cells successfully colonized into genital ridges of recipient, proliferate, differentiate and finally develop into functional donor gametes after they are transplanted into the body cavity of allogeneic or xenogeneic recipients. It is a powerful assisted reproductive technique for the conservation and propagation of the rare and endangered animals; meanwhile, it also provides an effective assay system for the functional analysis of germline stem cell. Germ cell transplantation in fish was first successfully performed in the model fish, zebrafish (Danio rerio); during the past decade, a series of breakthroughs have been achieved for this technique. Firstly, three types of fish germ cell transplantation have been established to produce donor-derived gametes by transplanting germ cells into recipients at diverse developmental stages, such as the blastula-stage embryos, newly hatched larvae, and adult fish. Secondly, the discovery of spermatogonia and oogonia stem cells has expanded the choice of donor germ cells. Thirdly, the method for selection and preparation of recipient has been improved. This technique has powerful applications in shortening the time of fish sexual maturity, sex control breeding and conservation of the rare and endangered fish, which has been studied and applied in a variety of teleost, including freshwater and marine fish. In this review, we systematically summarized the progress of germ cell transplantation in fish, pointed out the key points for the implementation of this technique, and discussed its promising application.