New Tools to Study Vascularisation in the Developing Embryo

Abstract

Our experiments in the avian embryo have uncovered the existence of two modes of endothelial network formation, depending on the germ layer associated with the mesoderm. When mesoderm is interacting with endoderm, it gives rise to endothelial precursors. Such is the case when splanchnopleura from 2 to 20 pairs of somites embryos or internal organ rudiments are transplanted from the quail in the chick or inversely. In contrast, when mesoderm is in contact with ectoderm, no intrinsic endothelial precursors appear; thus somatopleura or external organ rudiments are colonized by extrinsic precursors. We have detected a unique pattern of expression of the c-ets1 oncogene in endothelial cells. c-ets1 is turned on in endothelial cell nuclei of immature blood vessels and becomes inactive when the vessel wall differentiates. This expression, studied by in situ hybridization, appears as an interesting marker for emerging blood vessels and would be more efficiently analyzed at the level of the protein. Thus we are engaged in the preparation of a monoclonal antibody directed against one of the splicing products of the ets1 locus (p68 c-ets1). The use of this antibody will be combined with experimental approaches. We are also attempting to obtain cloned endothelial cell lines from the quail.