Analysis of the sequence and expression during sea urchin development of two members of a multigenic family, coding for butanol‐extractable proteins

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Abstract
Two cDNA clones related to Paracentrotus lividus butanol-extracted proteins, presumably belonging to cell surface proteins, were isolated by a λgt11 expression library of ovary poly A+ RNA. These clones, called bep 1 and bep4, of 1,110 and 1,071 bp, respectively, belong to a multigene family. By sequencing analysis, a special structural organization in the coding region is detected. A single copy region is inserted between two regions different from each other but similar in the two clones, which constitute two perfectly preserved domains in the genome and are not always present together in the various members of this gene family. The bep 1 and bep4 clones derive from two single genes that are polymorphic in the sea urchin genome. Expression of these clones was studied by Northern blot analysis. Both bep 1 and bep4 are transcribed during oogenesis into mRNAs of 1.4 kb, which are stored in eggs and utilized during early embryogenesis. None of these RNAs is, in fact, detectable after the gastrula stage. Moreover, the transcripts of three other members of the family are present in eggs and at the 32 cell stage, but they are also synthesized in the early developmental stages.