The univingene encodes a member of the transforming growth factor-β superfamily with restricted expression in the sea urchin embryo

We have identified a gene in the sea urchin Strongylocentrotus purpuratus that encodes a member of the transforming growth factor β(TGF-β) gene superfamily. We have named the gene univin, and it is the first member of thissuperfamily to be reported in echinoderms. The cDNA sequence predicts a 383-amino-acid residue protein with 7 cysteine residues characteristic of members of this superfamily and with a cluster of basic residues appropriately situated to signal proteolytic cleavage. Sequence comparisons place univin in the bone morphogenetic protein (BMP) group of the TGF-β superfamily along with thevertebrate BMPs, decapentaplegic protein from Drosophila, and Vg-1 from Xenopus. Analyses of univin expression in early embryos by RNA blots andin situ hybridization revealed the highest levelsof expression in the egg and prehatching blastula. During late cleavage stages, univin mRNA accumulation is progressively restricted to a circumequatorial band. Expression is further restricted during gastrulation when univin transcripts are detected primarily in the presumptive foregut and ciliated band. By pluteus stage, signals are detectable only in these cell types. The restricted temporal and spatial patterns of expression of univin during early blastula stages parallel those of SpAN, which encodes an astacin-like protease relatedto tolloid and BMP-1. The fact that these proteases are thought to function in the proteolyticactivation of TGF-β-related proteins that, respectively, regulate Drosophila embryonic dorsal-ventral patterning and vertebrate bone developmentsuggests that SpAN and univin could also have critical roles in early developmental decisionsin the sea urchin embryo.