RESEARCH ARTICLE r u n

DOI 10.1186/s12862-015-0329-xgian lineage (in teleost fishes), only two of them, SPP1 andParis-Seine, Paris UMR7138, France Full list of author information is available at the end of the article(ODAM), amelotin (AMTN) and secretory calcium-binding phosphoprotein-proline-glutamine-rich 1 (SCPP-PQ1) [1-5]. These three proteins play a role during enamel maturation, but their precise function is still debated. Similar to EMPs, AMTN is a proline/glutamine (P/Q) rich protein that belongs to the secretory calcium-binding phosphoprotein (SCPP) family, which comprises proteins plications of SPARC-L1 gave rise to the first members of bone, dentin and enamel SCPPs. The SCPP family ex-panded rapidly through tandem duplications as illustrated by the presence of ten SCPP genes (including AMTN, AMEL, ENAM and AMBN) in the coelacanth genome [12]. AMTN and the three EMPs were, therefore, present in the ancestral sarcopterygian genome 450 million years ago (Mya) [13] and probably earlier. However, so far, even if a number of SCPPs were identified in the actinoptery- * Correspondence