A family of proteins accumulating in ectoderm of sea urchin embryos specified by two related cDNA clones

Two cDNA clones, pSpec 1 and pSpec 2, had been selected previously as corresponding to transcripts greatly enriched in ectoderm of pluteus-stage larvae of the sea urchin, Stronglyocentrotus purpuratus. The two cDNA clones, corresponding to the 3′ ends of polysomal RNAs, have similar but distinct restriction maps. Messenger RNAs hybrid selected by these two cDNA clones were translated in a rabbit reticulocyte lysate cell-free system into the same set of 10 acidic proteins having molecular weights of 14–17,000 daltons. These in vitro products have positions identical or similar on two-dimensional gels to a group of proteins whose synthesis in vivo is highly enriched in the ectoderm. The 1.5- and 2.2-kb transcripts corresponding to pSpec 1 and pSpec 2 increase in prevalence by at least 100-fold during embryonic development. The rates of synthesis of these ectoderm proteins also increase by over 100-fold, though the patterns of change are distinct. It is likely that pSpec 1 and pSpec 2 correspond to mRNAs which are part of a small family of genes coding for the group of similar ectoderm proteins. These proteins and their mRNAs are enriched in ectoderm by the early gastrula stage.