EPITHELIAL V-LIKE ANTIGEN (EVA), A NOVEL MEMBER OF THE IMMUNOGLOBULINSUPERFAMILY, EXPRESSED IN EMBRYONIC EPITHELIA WITH A POTENTIAL ROLE AS HOMOTYPIC ADHESION MOLECULE IN THYMUS HISTOGENESIS

Thymus development depends on a complex series of interactions between thymocytes and the stromal component of the organ, To identify regula ted genes during this codependent developmental relationship, we have applied an RNA fingerprinting technique to the analysis of thymus expa nsion and maturation induced in recombinase-deficient mice injected wi th anti-CD3 antibodies, This approach led us to the identification of a gene encoding a new member of the immunoglobulin superfamily, named epithelial V-like antigen (EVA), which is expressed in thymus epitheli um and strongly downregulated by thymocyte developmental progression. This gene is expressed in the thymus and in several epithelial structu res early in embryogenesis. EVA is highly homologous to the myelin pro tein zero and, in thymus-derived epithelial cell lines, is poorly solu ble in nonionic detergents, strongly suggesting an association to the cytoskeleton. Its capacity to mediate cell adhesion through a hemophil ic interaction and its selective regulation by T cell maturation might imply the participation of EVA in the earliest phases of thy thymus o rganogenesis.