Animal Reproduction Science 95 (2006) 67–74 Selective decrease of chick embryonic primordial germ cells in vivo and in vitro by soft X-ray irradiation Jeong M. Lim a , Huck M. Kwon a , Duk K. Kim a , Jin N. Kim b , Tae S. Park a , Tamao Ono c , Jae Y. Han a,∗ a Department of Food and Animal Biotechnology, Seoul National University, Seoul 151-921, Republic of Korea b Avicore Biotechnology Institute Inc., Hanlim Human Tower #707, Gyeonggi-Do 435-050, Republic of Korea c Faculty of Agriculture, Shinshu University, Minamiminowa, Nagano 399-4598, Japan Received 11 July 2005; accepted 14 September 2005 Available online 17 October 2005 Abstract The feasibility of soft (low-energy) X-ray irradiation as a means of depleting the endogenous primor- dial germ cell(s) (PGC) of chicken embryos, to improve the efficiency of germ cell-mediated transgenesis, was investigated. Eggs were subjected to a non-irradiated control treatment and embryos were exposed for 40 s to soft X-ray at 15, 16.5, or 18 kV (∼1.5, 1.65, and 1.8Gy, respectively). Exposure of stage X embryos to each dose of X-ray resulted in a reduction of ∼50% in the number of PGC apparent at stage 28, whereas the total number of gonadal cells was unaffected. Irradiation (16.5 kV) of embryos at stage 9 or 14 also resulted in similar decreases in the number of PGC with no effect on the total number of gonadal cells. Irradiation did not affect embryo hatchability, compared with the non-irradiated control treatment, although the hatch rate increased with the age of embryos at the time of irradiation. Expo- sure of gonadal cells isolated from stage 28 embryos to X-ray (16.5kV, ∼0.8 Gy) prevented the increase in PGC number during subsequent culture for 10 days; the increase in the total number of gonadal cells was not affected. In conclusion, exposure of chicken embryos to a low dose of soft X-rays is effec- tive for depleting the endogenous PGC population without affecting embryo hatchability or somatic cell viability. © 2005 Elsevier B.V. All rights reserved. Keywords: Chicken; Primordial germ cell; Gonadal cell; X-irradiation; Hatchability; Cell viability ∗ Corresponding author. Tel.: +82 2 880 4810; fax: +82 2 874 4811. E-mail address: jaehan@snu.ac.kr (J.Y. Han). 0378-4320/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.anireprosci.2005.09.006