title: Amelotin: an enamel matrix protein that experienced distinct evolutionary histories in amphibians, sauropsids and mammals.
abstract: BACKGROUND
  Amelotin (AMTN) is an ameloblast-secreted protein that belongs to the secretory calcium-binding phosphoprotein (SCPP) family, which originated in early vertebrates. In rodents, AMTN is expressed during the maturation stage of amelogenesis only. This expression pattern strongly differs from the spatiotemporal expression of other ameloblast-secreted SCPPs, such as the enamel matrix proteins (EMPs). Furthermore, AMTN was characterized in rodents only. In this study, we applied various approaches, including in silico screening of databases, PCRs and transcriptome sequencing to characterize AMTN sequences in sauropsids and amphibians, and compared them to available mammalian and coelacanth sequences.
  
  
  RESULTS
  We showed that (i) AMTN is tooth (enamel) specific and underwent pseudogenization in toothless turtles and birds, and (ii) the AMTN structure changed during tetrapod evolution. To infer AMTN function, we studied spatiotemporal expression of AMTN during amelogenesis in a salamander and a lizard, and compared the results with available expression data from mouse. We found that AMTN is expressed throughout amelogenesis in non-mammalian tetrapods, in contrast to its expression limited to enamel maturation in rodents.
  
  
  CONCLUSIONS
  Taken together our findings suggest that AMTN was primarily an EMP. Its functions were conserved in amphibians and sauropsids while a change occurred early in the mammalian lineage, modifying its expression pattern during amelogenesis and its gene structure. These changes likely led to a partial loss of AMTN function and could have a link with the emergence of prismatic enamel in mammals.
authors.affiliation: Institut de Biologie Paris-Seine, Université Pierre et Marie Curie, Evolution Paris-Seine, Paris, UMR7138, France. barbara.gasse@gmail.com.
authors.forename: Barbara
authors.initials: B
authors.lastname: Gasse
authors.affiliation: Department of Biology, University of South Alabama, Mobile, AL, 36688, USA. yle@yleniachiari.it.
authors.forename: Ylenia
authors.initials: Y
authors.lastname: Chiari
authors.affiliation: Institut de Biologie Paris-Seine, Université Pierre et Marie Curie, Evolution Paris-Seine, Paris, UMR7138, France. silvent.jeremie@gmail.com.|Department of Structural Biology, Weizmann Institute of Science, Rehovot, 76100, Israel. silvent.jeremie@gmail.com.
authors.forename: Jérémie
authors.initials: J
authors.lastname: Silvent
authors.affiliation: Institut de Biologie Paris-Seine, Université Pierre et Marie Curie, Evolution Paris-Seine, Paris, UMR7138, France. tiphaine.davit-beal@upmc.fr.
authors.forename: Tiphaine
authors.initials: T
authors.lastname: Davit-Béal
authors.affiliation: Institut de Biologie Paris-Seine, Université Pierre et Marie Curie, Evolution Paris-Seine, Paris, UMR7138, France. jean-yves.sire@upmc.fr.
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Sire
mesh_terms: D000566:Amelogenesis; D000818:Animals; D001483:Base Sequence; D003743:Dental Enamel / Q000378:metabolism; D003746:Dental Enamel Proteins / Q000235:genetics* / Q000378:metabolism*; D019143:Evolution, Molecular; D008322:Mammals / Q000235:genetics; D008969:Molecular Sequence Data; D012326:RNA Splicing; D016415:Sequence Alignment; D014714:Vertebrates / Q000145:classification / Q000235:genetics*
chemical_list: D003746:Dental Enamel Proteins; C109069:enamel matrix proteins