title: X-irradiation removes endogenous primordial germ cells (PGCs) and increases germline transmission of donor PGCs in chimeric chickens.
abstract: Primordial germ cells (PGCs) are embryonic precursors of germline cells with potential applications in genetic conservation, transgenic animal production and germline stem cell research. These lines of research would benefit from improved germline transmission of transplanted PGCs in chimeric chickens. We therefore evaluated the effects of pretransplant X-irradiation of recipient embryos on the efficacy of germline transmission of donor PGCs in chimeric chickens. Intact chicken eggs were exposed to X-ray doses of 3, 6 and 9 Gy (dose rate = 0.12 Gy/min) after 52 h of incubation. There was no significant difference in hatching rate between the 3-Gy-irradiated group and the nonirradiated control group (40.0 vs. 69.6%), but the hatching rate in the 6-Gy-irradiated group (28.6%) was significantly lower than in the control group (P<0.05). No embryos irradiated with 9 Gy of X-rays survived to hatching. X-irradiation significantly reduced the number of endogenous PGCs in the embryonic gonads at stage 27 in a dose-dependent manner compared with nonirradiated controls. The numbers of endogenous PGCs in the 3-, 6- and 9-Gy-irradiated groups were 21.0, 9.6 and 4.6% of the nonirradiated control numbers, respectively. Sets of 100 donor PGCs were subsequently transferred intravascularly into embryos irradiated with 3 Gy X-rays and nonirradiated control embryos. Genetic cross-test analysis revealed that the germline transmission rate in the 3-Gy-irradiated group was significantly higher than in the control group (27.5 vs. 5.6%; P<0.05). In conclusion, X-irradiation reduced the number of endogenous PGCs and increased the germline transmission of transferred PGCs in chimeric chickens.
authors.affiliation: Division of Germ Cell Biology, National Institute for Basic Biology, National Institute of Natural Sciences, Aichi 444-8787, Japan. ynsu@nibb.ac.jp
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Fumitake
authors.initials: F
authors.lastname: Usui
authors.forename: Daichi
authors.initials: D
authors.lastname: Miyahara
authors.forename: Takafumi
authors.initials: T
authors.lastname: Mori
authors.forename: Tamao
authors.initials: T
authors.lastname: Ono
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kagami
authors.forename: Kumiko
authors.initials: K
authors.lastname: Takeda
authors.forename: Keijiro
authors.initials: K
authors.lastname: Nirasawa
authors.forename: Takahiro
authors.initials: T
authors.lastname: Tagami
mesh_terms: D000822:Animal Husbandry / Q000379:methods; D000818:Animals; D017849:Animals, Inbred Strains; D002642:Chick Embryo / Q000166:cytology / Q000196:embryology / Q000254:growth & development / Q000528:radiation effects*; D002645:Chickens; D004307:Dose-Response Relationship, Radiation; D047108:Embryonic Development / Q000528:radiation effects*; D005240:Feasibility Studies; D005260:Female; D005854:Germ Cells / Q000166:cytology / Q000528:radiation effects* / Q000637:transplantation*; D018095:Germ-Line Mutation / Q000528:radiation effects*; D006066:Gonads / Q000166:cytology / Q000196:embryology / Q000528:radiation effects*; D006085:Graft Survival; D007150:Immunohistochemistry / Q000662:veterinary; D008297:Male; D011828:Radiation Chimera / Q000196:embryology* / Q000254:growth & development; D011830:Radiation Effects; D016019:Survival Analysis; D014965:X-Rays