Conflicts of interest: None.
SCPP genes in the coelacanth: Tissue mineralization genes shared by sarcopterygians
Article first published online: 8 NOV 2013
© 2013 Wiley Periodicals, Inc.
Journal of Experimental Zoology Part B: Molecular and Developmental Evolution
Special Issue: Genome of the African Coelacanth
Volume 322, Issue 6, pages 390–402, September 2014
How to Cite
2013. SCPP genes in the coelacanth: Tissue mineralization genes shared by sarcopterygians. J. Exp. Zool. (Mol. Dev. Evol.) 322B:390–402., .
- Issue published online: 6 AUG 2014
- Article first published online: 8 NOV 2013
- Manuscript Accepted: 4 OCT 2013
- Manuscript Revised: 2 AUG 2013
- Manuscript Received: 8 MAY 2013
- The National Science Foundation. Grant Numbers: BCS0725227, BCS0343442, MCB0719558
- The Pennsylvania State University; Evan Pugh Professors Research Fund
The coelacanth is the basal-most extant sarcopterygian that has teeth and tooth-like structures, comprising bone, dentin, and enamel or enameloid. Formation of these tissues involves many members of the secretory calcium-binding protein (SCPP) family. In tetrapods, acidic-residue-rich SCPPs are used in mineralization of bone and dentin, whereas Pro/Gln-rich SCPPs participate in enamel formation. Teleosts also employ many SCPPs for tissue mineralization. Nevertheless, the repertoire of SCPPs is largely different in teleosts and tetrapods; hence, filling this gap would be critical to elucidate early evolution of mineralized tissues in osteichthyans. In the present study, we searched for SCPP genes in the coelacanth genome and identified 11, of which two have clear orthologs in both tetrapods and teleosts, seven only in tetrapods, and two in neither of them. Given the divergence times of these vertebrate lineages, our discovery of this many SCPP genes shared between the coelacanth and tetrapods, but not with teleosts, suggests a complicated evolutionary scheme of SCPP genes in early osteichthyans. Our investigation also revealed both conserved and derived characteristics of SCPPs in the coelacanth and other vertebrates. Notably, acidic SCPPs independently evolved various acidic repeats in different lineages, while maintaining high acidity, presumably important for interactions with calcium. Furthermore, the three Pro/Gln-rich SCPP genes, required for mineralizing enamel matrix and confirmed only in tetrapods, were all identified in the coelacanth, strongly suggesting that enamel is equivalent in the coelacanth and tetrapods. This finding corroborates the previous proposition that true enamel evolved much earlier than the origin of tetrapods. J. Exp. Zool. (Mol. Dev. Evol.) 322B: 390–402, 2014. © 2013 Wiley Periodicals, Inc.