FISH ES CELLS AND APPLICATIONS TO BIOTECHNOLOGY

ES cells provide a promising tool for the generation of transgenic animals with site-directed mutations. When ES cells colonize germ cells in chimeras, transgenic animals with modified phenotypes are generated, either used for functional genomics studies in the lab or improving productivity in commercial settings. Although the ES cell approach has been limited to mice, there is high interest for developing the technology in fish. In this review, we describe the step-by-step procedure for developing ES cells in fish. Key aspects include avoiding cell differentiation, specific in vitro traits of pluripotency and, most importantly, testing for production of chimeric animals as the main evidence of pluripotency. The whole process focuses on two model species, zebrafish and medaka, in which most work has been done. The achievements attained in these species, as well as their applicability to other commercial fish are discussed. Due to the difficulties on the germ line competence, mostly of long-term fish ES cells, alternative cell-based approaches, such as primordial germ cells and nuclear transfer need to be considered. Although progress to date has been slow, there are promising achievements in homologous recombination and alternative avenues yet to be taken, that can bring ES technology in fish to fruition.