EXPRESSION OF ALPHA(4) INTEGRIN MESSENGER-RNA AND PROTEIN AND FIBRONECTIN IN THE EARLY CHICKEN-EMBRYO

alpha(4) integrins (alpha(4) beta(1) and alpha(4) beta(7)) have been s hown to mediate both cell-matrix adhesion to fibronectin and cell-cell adhesion to VCAM-1. These interactions have been suggested to contrib ute to hematopoiesis, lymphocyte homing, recruitment of inflammatory c ells, neural crest cell migration and myogenesis. We report here the c loning of chicken alpha(4) cDNA and its use to define the patterns of expression of alpha(4) mRNA and protein in early chicken embryos (19-2 2 somite pairs), a stage at which neural crest cells can be examined a t various points in their migration and semitic development and differ entiation can also be observed at various stages. We observe widesprea d expression of both alpha(4) mRNA and protein, although the patterns of steady state expression do not conform precisely. Many neural crest cells contain significant levels of alpha(4) mRNA. Some neural crest cells express alpha(4) protein but its expression is transient and/or limited to a subset of these cells. alpha(4) is strongly expressed at both mRNA and protein levels by semitic cells and their derivatives in the sclerotome, dermatome and myotome and is also expressed in neural tube, otic placode, heart, gut endoderm and some other tissues. Compa rison with the distributions of fibronectin shows that, although some alpha(4) expression occurs in locations consistent with a role in cell -matrix adhesion to fibronectin, alpha(4) is also expressed in other p laces where fibronectin is low or absent and a role for alpha(4) in ce ll-cell interactions appears more likely.