Decrease in the number of primordial germ cells following injection of the animal pole cytoplasm into the vegetal pole region of Xenopus Eggs

Abstract Effects of the egg cytoplasm on the formation of primordial germ cells (PGCs) were examined through microinjection into the subcortical cytoplasm near the vegetal pole of Xenopus laevis eggs. Injection of vegetal pole cytoplasm and physiological saline did not reduce the number of PGCs. However, the average number of PGCs in tadpoles at stage 46 decreased to about 60% of that in normal controls when the animal pole cytoplasm of fertilized eggs was injected into the intact eggs. Similar effects were observed when the animal pole cytoplasm of fertilized or unfertilized eggs was injected into eggs irradiated with a low dose of ultraviolet light. These facts suggest the possibility that inhibitor(s) of PGC formation exists in the animal pole cytoplasm of both fertilized and unfertilized eggs.