Identification of new bone morphogenetic protein-related members in invertebrates.

Although believed to be widely distributed among the animal kingdom, transforming growth factor-beta (TGF-beta) superfamily members have mainly been characterized in vertebrate and in invertebrate model organisms such as Drosophila and C. elegans. To characterize such new factors in invertebrates, a PCR screen was performed on genomic DNA from different animal phyla, using degenerate primers deduced from consensus sequences of known members of the TGF-beta superfamily. Four new members were identified from a cnidaria, an echinoderm and from two classes of molluscs. These new proteins exhibit a high degree of identity with human bone morphogenetic proteins (BMP2/4). Sequence comparisons suggest an early origin and an evolutionary conservation of the molecular conformation. However, their possible involvement in distinct regulatory pathways is discussed.