Cloning and characterization of cDNAs encoding the integrin α2 and α3 subunits from Xenopus laevis

Integrins containing the a2 and a3 subunits associate with the b1 subunit to form distinct receptors with partially overlapping adhesive specificities. We report the cloning and sequence of cDNAs that encode the Xenopus orthologues of integrins a2 and a3 and the expression of these subunits during embryogenesis. Integrin a2 and a3 mRNAs are first expressed in the dorsal mesoderm and developing notochord at gastrulation. We also show that a3 mRNAs are expressed in the entire marginal zone of gastrulae dorsalized with LiCl but that this localization is lost in embryos ventralized by ultraviolet light. Immunoblots reveal that the a3 protein is expressed throughout early development, however, the a2 protein is not detected until late tailbud stages. Injection of full-length a3 transcripts into the animal poles of fertilized eggs results in embryonic defects in paraxial mesoderm attributed to the failure of somites to form segments. Injection of the a3 transcripts into the vegetal pole and overexpression of a 5′-truncated a3 control construct have no apparent affect on development or somite formation. These data suggest that normal position-specific expression of integrins is important in maintaining the proper organization of tissues during early amphibian morphogenesis.  1997 Elsevier Science Ireland Ltd.