Does the paraxial mesoderm of the avian embryo have hemangioblastic capacity?

In a previous study of the hemangioblastic capacity of lateral plate mesoderm, we showed that the endoderm-associated splanchnopleural layer is capable of giving rise to both endothelial and hemopoietic cells while the ectoderm-associated somatopleural layer is not (Pardanaud and Dieterlen-Lièvre 1993a). In order to complete the inventory of territories able to produce these two cell lineages, we assayed the paraxial mesoderm, and report the results here. Quail somites or segmental plates were treated with mab QH1+complement in order to eliminate attached aortic endothelial cells, which cling to the ventral aspects of these structures. They were grafted in the limb bud or the coelom of chick host, since these sites promote the differentiation of endothelial and hemopoietic cells, respectively. Vascular development and hemopoietic cell emergence were analyzed using QH1 immunocytology. Segmental plate and somites both produced abundant endothelial cells. In addition, the segmental plate gave rise to small groups of hemopoietic cells when grafted in the coelom.