Cloning, expression, and localization of a new member of a Paracentrotus lividus cell surface multigene family.

We have isolated and characterized a cDNA clone corresponding to a new member of bep (butanol, extracted, proteins) Paracentrotus lividus multigene family coding for cell surface proteins. The cDNA, called bep3, encodes a 370 amino acid protein and shares the same structural organization in the coding region with other members of the same gene family already characterized. Expression of this clone studied by Northern blot and by whole mount hybridization shows that the bep3 messenger is transcribed during oogenesis and utilized till the gastrula stage, whereas at the prism stage, unlike other members of the same gene family, new synthesis of messenger occurs. By whole mount hybridization spatial distribution of bep3 messenger in egg and embryos is established. This messenger appears located in the animal half of the unfertilized egg and moves to the cortical zone after fertilization; it is not present in the structures derived by the vegetal part of the embryo, such as the micromeres of the 16-cell stage, the primary mesenchyme cells of the blastula, and the primary intestine of the gastrula. At the prism stage instead, hybridization of bep3 messenger is restricted to the part of the embryo that will give origin to the oral region as successively confirmed by hybridization at the pluteus stage. The result of whole mount hybridization was confirmed by Northern blot hybridization of separated meso-macromere and micromere RNAs. A Southern blot experiment demonstrates that bep3 is codified by a single copy gene. Conservation of the bep multigene family in several Mediterranean and Japanese sea urchin species has also been analyzed.