M. Hung et al., CHARACTERIZATION AND LOCALIZED EXPRESSION OF THE LAMININ-BINDING PROTEIN P40 (LBP/P40) GENE DURING SEA-URCHIN DEVELOPMENT/, Experimental cell research, 221(1), 1995, pp. 221-230
We have isolated and characterized the expression of a cDNA clone from
the sea urchin Strongylocentrotus purpuratus that encodes a protein v
ery similar to LBP/p40, originally identified as a nonintegrin, 67-kDa
laminin binding protein. The deduced amino acid sequence of the prote
in, which we call spLBP/p40, shows significant similarity with the LEP
/p40 from other sources, although significant divergence does occur at
the carboxyl end. The S. purpuratus mRNA is present as a maternal tra
nscript and its level remains constant until activation of zygotic tra
nscription at the hatching blastula stage, whereupon the total spLBP/p
40 increases through the pluteus larval stage. Adult tissues also cont
ain the spLBP/p40 mRNA. Both maternal and zygotic transcripts are tran
slated as determined by their presence in polysomes. Immunoblot analys
is using an antibody raised against a recombinant fusion protein indic
ates that the concentration of the spLBP/p40 protein remains constant
during development despite the postblastula increase in mRNA concentra
tion. However, the spatial distribution of the protein changes from a
uniform, intracellular distribution in all cells of cleavage and blast
ula stages to localized, elevated levels in cells of the gut, primary
mesenchyme, and oral epithelium of prism larvae. The distribution of s
pLBP/p40 mRNA at different developmental stages, analyzed by in situ h
ybridization, reflects that of the protein. Our results argue against
a laminin binding function for this protein; instead they place the sp
LBP/p40 gene in a class of previously described sea urchin genes invol
ved in growth and proliferation. (C) 1995 Academic Press, Inc.