Developmental characterization of the gene for laminin α-chain in sea urchin embryos

We describe the isolation and characterization of a cDNA clone encoding a region of the carboxy terminal globular domain (G domain) of the α-1 chain of laminin from the sea urchin, Strongylocentrotus purpuratus. Sequence analysis indicates that the 1.3 kb cDNA (spLAM-α) encodes the complete G2 and G3 subdomains of sea urchin a-laminin. The 11 kb spLAM-α mRNA is present in the egg and declines slightly in abundance during development to the pluteus larva. The spLAM-α gene is also expressed in a variety of adult tissues. Whole mount in situ hybridization of gastrula stage embryos indicates that ectodermal and endodermal epithelia and mesenchyme cells contain the spLAM-α mRNA. Immunoprecipitation experiments using an antibody made to a recombinant fusion protein indicates spLAM-α protein is synthesized continuously from fertilization as a 420 kDa protein which accumulates from low levels in the egg to elevated levels in the pluteus larva. Light and electron microscopy identify spLAM-α as a component of the basal lamina. Blastocoelic microinjection of an antibody to recombinant spLAM-α perturbs gastrulation and skeleton formation by primary mesenchyme cells suggesting an important role for laminin in endodermal and mesodermal morphogenesis.