Irradiation of fish embryos prior to blastomere transfer boosts the colonisation of their gonads by donor-derived gametes

Blastomere transplantation into fish blastula embryos results in somatic ch imeras, which generally provide null or a small proportion of gametes deriv ed from the donor. This may partly explain why none of the ES-like cell lin es established from fish embryos has contributed to the germline of chimera s when transplanted at the blastula stage. Here, we report that a moderate gamma-irradiation of recipient embryos, followed by transplantation of disp ersed blastomeres, considerably enhances the proportion of donor-derived ga metes (53% versus 5% in average). In fish, the resulting protocol should ma ximise the pluripotency level measured in vivo for embryonic cell lines and for cultured germ cells. (C) 1999 Wiley-Liss, Inc.