Effects of Soft X-Ray Irradiation to Stage X Blastoderm on Restriction of Proliferation of Primordial Germ Cells in Early Chicken Embryos

Abstract

It is necessary to deplete the endogenous primordial germ cells (PGCs) from recipient embryos when germline chimaeric chickens are produced by the transfer of PGCs. In this study, effects of soft X-ray irradiation on the restriction of PGC proliferation were examined to obtain recipient embryos with as many depleted PGCs as possible. The stage X blastoderm was irradiated with soft X-rays (15 kVP, 5mA, 0.083nm, 16 cm distance) for 20-180 seconds (0.27-2.4Gy), and concentrations of PGCs in the bloodstream of embryos at stages 13-16 were analysed. The viabilities of embryos irradiated with soft X-rays for 20-90 seconds was not significantly different from those in the control, but were markedly reduced when embryos were irradiated with soft X-rays for 120-180 seconds. The concentration of PGCs in the bloodstream of embryos was reduced by increasing the irradiation time of soft X-rays. In particular, the concentration of PGCs at stages 14-15 started to decrease rapidly when irradiated with soft X-rays for more than 90 seconds. Administration of busulfan in the stage X blastoderm showed a similar effect to soft X-ray irradiation on the concentration of PGCs in the bloodstream of embryos. Our results suggest that a 90-second irradiation of soft X-rays to the stage X blastoderm is recommended for reducing the concentration of PGCs in chicken embryos without affecting their viability.

Keywords

• chick embryo
• primordial germ cell
• soft x-ray
• stage x blastoderm