Somatic and Germline Chicken Chimeras Obtained from Brown and White Leghorns by Transfer of Early Blastodermal Cells

Abstract

Stage × blastodermal cells were isolated from freshly laid unincubated Brown Leghorn chicken eggs. Five hundred cells from Stage × Brown Leghorn embryos were injected into the subgerminal cavity of White Leghorn unincubated embryos exposed to 550 rad of γ irradiation from a cesium-137 source. Of 712 White Leghorn embryos that were irradiated and injected with Brown Leghorn blastodermal cells, 52 (7.3%) survived to hatching. Somatic chimerism was examined in the melanocyte population and erythroid lineage. The presence of brown feathers indicating donor cell contribution to melanocyte pigmentation was observed in 23 (44%) out of the 52 hatched chicks. Analysis of blood DNA was performed using a probe that revealed an endogenous retroviral gag fragment specific for the donor genome. Three out of these 23 chimeric chickens exhibited the gag-specific fragment. To test germline chimerism, chickens that reached sexual maturity were mated with Brown Leghorns. Three somatically chimeric hens produced Brown Leghorn progeny at a rate of 30.7, 9.2, and 2.9% respectively, thus proving donor cell contribution to the germline differentiation. Chimeric chickens obtained after injection of nonirradiated embryos exhibited a lower extent of chimerism at the feather level and did not show any chimerism in the erythroid lineage and the germline, thus demonstrating the value of the use of compromised recipient embryos to produce chimeras in chickens. Nevertheless, the extent of somatic chimerism could not be used to predict the germline chimerism.