Characterization of Sparus aurata osteonectin cDNA and in silico analysis of protein conserved features: evidence for more than one osteonectin in Salmonidae.

Osteonectin is a matricellular protein involved in various cellular mechanisms but its exact function remains unclear despite numerous studies. We present here the cloning of Sparus aurata partial osteonectin cDNA and the reconstruction of 15 other sequences from both vertebrates and invertebrates, almost doubling the set of available sequences (a total of 35 sequences is now available). Taking advantage of the resulting large amount of data, we have created multiple sequence alignments and identified osteonectin putative conserved features (intra- and inter-disulfide bonds, collagen- and calcium-binding domains and phosphorylation sites) likely to be important for protein structure and function. This work also provides the first evidence for the presence of more than one osteonectin in some species. Finally, S. aurata osteonectin gene expression has been shown to initiate during larval development shortly after gastrulation, and to be high in bone-derived cell lines while down-regulated during extracellular matrix mineralization, further emphasizing the important role of osteonectin in skeletal development and bone formation.