TRANSFORMATION OF CARDIAC ENDOTHELIUM INTO CUSHION MESENCHYME IS DEPENDENT ON ES 130 - TEMPORAL, SPATIAL, AND FUNCTIONAL-STUDIES IN THE EARLY CHICK-EMBRYO/

ES/130 is a novel 130-kDa protein that has been linked previously to t he transformation of endocardial endothelium into cushion mesenchyme. In the present study we report the localization of protein and mRNA fo r ES/130 in stages 7-plus through 20 chick embryos and present functio nal data related to a potential mechanism for ES/130, The temporal and spatial regulation of ES/130 expression suggests that this epithelial -to-mesenchymal transformation is a result of homogenetic induction. F unctional studies indicate that myocardially derived ES/130 elicits ex pression of this protein by target AV endothelial cells, which is link ed to a signal transduction cascade. The localization of ES/130 to oth er sites of inductive interactions (e.g., limb bud ectoderm, gut, and notochord) implies that this protein may have a more widespread import ance to embryogenesis beyond its involvement in cardiac cushion tissue formation.