Proliferation and migration of primordial germ cells in We/We mouse embryos

Abstract

We have examined the numbers and distribution of primordial germ cells in W^e/W^e, W^e/+, and +/+ mouse embryos using Southern blotting to determine embryo genotypes. At early somite stages (5–7 somites: approximately 81/2 days post coitum [dpc]) there are 50 to 100 germ cells in embryos of all genotypes. The number of germ cells in W^e/+ and +/+ embryos then begins to increase: at later somite stages (17–19 somites: approximately 91/2 dpc) they number about 200, and by 101/2 dpc there are approximately 725W^e/+ and 850 +/+ germ cells. During this time, however, the number of germ cells in W^e/W^e embryos remains less than 100. At 81/2 dec, the distribution of germ cells in the hindgut endoderm is the same in all genotypes. By 91/2 dpc, 30% of W^e/W^e germ cells are found in ectopic sites (allantois and vitelline artery); germ cell distribution along the length of the hindgut appears normal, but germ cells remain confined to the floor of the gut in W^e/W^e embryos, rather than being distributed around its circumference as in the other two genotypes. By 101/2 days, the migration of W^e/W^e germ cells through the dorsal mesentery lags behind that of the other genotypes, and a larger proportion remains in the gut wall.