EXPRESSION OF TGF-BETA-1 BETA-3 DURING EARLY CHICK-EMBRYO DEVELOPMENT/

We have used an antibody against a TGF beta peptide fragment to locali ze this growth factor in the early chick embryo from laying to the ten -somite stage of development. Western blotting showed that the antibod y reacted with both mammalian TGF beta 1 and chicken TGF beta 3. By im munocytochemistry we find that at the earliest developmental stage (st age X of Eyal-Giladi and Kochav) immunoreactivity to this antibody is primarily located in the cells of the area opaca and marginal zone, as well as in the most peripheral edge cells of the blastoderm. The yolk is non-reactive, except in a highly localized region subjacent to the edge cells. This pattern persists at stage XII, and at both stages in dividual isolated cells in the epiblast and hypoblast are also reactiv e. By the time of gastrulation, reactivity in the epiblast is polarize d to the ventral extremity of the cells, and again some isolated cells in this layer are intensely immunoreactive. At this stage also, the e ndoderm cells, particularly those underlying the primitive streak, are positive, as are the mesoderm cells lateral to the streak. At somite stages, the neuroepithelium is not reactive but the ectoderm lateral t o it is strongly positive. At the caudal primitive streak levels of ea rly somite embryos, the ectoderm and endoderm are immunoreactive while the mesoderm loses the reactivity it showed at the early gastrulation stages. The neuroepithelial cells later show reactivity at their apic al poles, and, as at the earlier stages, individual cells show intense labelling. These results indicate that TGF beta 1 and/or TGF beta 3 i mmunoreactivity is developmentally regulated from very early stages of morphogenesis in the chick, and together with data from earlier funct ional studies, suggest that this factor has roles in embryonic axis fo rmation and in blastoderm expansion. (C) 1994 Wiley-Liss, Inc.