Restriction of proliferation of primordial germ cells by the irradiation of Japanese quail embryos with soft X-rays

Primordial germ cells (PGCs) are the progenitor cells for the gametes. Avia n PGCs are located in the central region of the area pellucida at the blast oderm stage. Shortly after further incubation, they migrate to the extra-em bryonic germinal crescent, and then as soon as the blood vessels form, they enter the circulation and finally settle in the gonadal primordium. We hav e developed a simple method using soft X-ray irradiation (18 kV power, 20 c m distance) to reduce the number of PGCs in Japanese quail embryos, which s hould be useful in preparing recipient embryos for PGC-transfer studies. Wh en embryos were exposed to the soft X-rays for 40 s before incubation, the concentration of circulating PGCs was less than one-fifth that in controls after 2 days of incubation. Embryos at day 6 of incubation contained approx imately half the number of PGCs compared to controls when they were exposed before or at day 2 of incubation. Irradiation for 40 s is recommended taki ng into consideration the restriction of proliferation of PGCs, and viabili ty and hatchability. (C) 2001 Elsevier Science Inc. All rights reserved.