GEPHE SUMMARY
Gephebase Gene
Entry Status
Published
GepheID
GP00001934
Main curator
Courtier
PHENOTYPIC CHANGE
Trait Category
Trait State in Taxon A
presence of teeth
Trait State in Taxon B
absence of teeth
Ancestral State
Taxon A
Taxonomic Status
Taxon A
Common Name
Cuvier's dwarf caiman
Synonyms
Cuvier's dwarf caiman; MNHN 7530; MNHN:7530
Rank
species
Lineage
Show more ... ta; Gnathostomata; Teleostomi; Euteleostomi; Sarcopterygii; Dipnotetrapodomorpha; Tetrapoda; Amniota; Sauropsida; Sauria; Archelosauria; Archosauria; Crocodylia; Alligatoridae; Caimaninae; Paleosuchus
NCBI Taxonomy ID
is Taxon A an Infraspecies?
No
Taxon B
Latin Name
Common Name
chicken
Synonyms
Gallus gallus domesticus; chicken; bantam; chickens
Rank
species
Lineage
Show more ... pha; Tetrapoda; Amniota; Sauropsida; Sauria; Archelosauria; Archosauria; Dinosauria; Saurischia; Theropoda; Coelurosauria; Aves; Neognathae; Galloanserae; Galliformes; Phasianidae; Phasianinae; Gallus
NCBI Taxonomy ID
is Taxon B an Infraspecies?
No
GENOTYPIC CHANGE
Presumptive Null
Yes
Molecular Type
Aberration Type
Deletion Size
10-100 kb
Molecular Details of the Mutation
synteny of the corresponding region - the gene has been likely deleted from the chicken genome as a consequence of intrachromosomal rearrangements which have probably occurred in the lineage that led to the last common ancestor of modern birds
Experimental Evidence
Authors
Sire JY; Delgado SC; Girondot M
Abstract
The ability to form teeth was lost in an ancestor of all modern birds, approximately 100-80 million years ago. However, experiments in chicken have revealed that the oral epithelium can respond to inductive signals from mouse mesenchyme, leading to reactivation of the odontogenic pathway. Recently, tooth germs similar to crocodile rudimentary teeth were found in a chicken mutant. These "chicken teeth" did not develop further, but the question remains whether functional teeth with enamel cap would have been obtained if the experiments had been carried out over a longer time period or if the chicken mutants had survived. The next odontogenetic step would have been tooth differentiation, involving deposition of dental proteins.

Using bioinformatics, we assessed the fate of the four dental proteins thought to be specific to enamel (amelogenin, AMEL; ameloblastin, AMBN; enamelin, ENAM) and to dentin (dentin sialophosphoprotein, DSPP) in the chicken genome. Conservation of gene synteny in amniotes allowed definition of target DNA regions in which we searched for sequence similarity. We found the full-length chicken AMEL and the only N-terminal region of DSPP, and both are invalidated genes. AMBN and ENAM disappeared after chromosomal rearrangements occurred in the candidate region in a bird ancestor.

These findings not only imply that functional teeth with enamel covering, as present in ancestral Aves, will never be obtained in birds, but they also indicate that these four protein genes were dental specific, at least in the last toothed ancestor of modern birds, a specificity which has been questioned in recent years.
Additional References
RELATED GEPHE
Related Haplotypes
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