Evolutionary Enamel Loss Linked To Molecular Decay Of Enamel-specific Gene

Main Category: Genetics
Article Date: 04 Sep 2009 - 16:00 PDT

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Researchers newly report correlation of the progressive loss of enamel in the fossil record with a simultaneous molecular decay of a gene involved in enamel formation in mammals. Details are published in the September 4 issue of the open-access journal PLoS Genetics.

Enamel is the hardest substance in the vertebrate body. One of the key proteins involved in enamel formation is enamelin. Most placental mammals have teeth that are capped with enamel, but there are also lineages without teeth, such as anteaters, pangolins and baleen whales, or with enamelless teeth, such as armadillos, sloths, aardvarks and pygmy and sperm whales. All toothless and enamelless mammals are descended from ancestral forms that possessed teeth with enamel.

Given this ancestry, the researchers hypothesized that mammalian species without teeth or with teeth that lack enamel would have copies of the gene that codes for the enamelin protein, but that the enamelin gene in these species would contain mutations that render it a nonfunctional pseudogene. To test this hypothesis, they sequenced most of the protein-coding region of the enamelin gene in all groups of placental mammals that lack teeth or have enamelless teeth.

In every case, they discovered mutations in the gene that disrupt the proper reading frame that codes for the enamelin protein. The results link evolutionary change at the molecular level to morphological change in the fossil record.

"Currently, we are actively engaged in deciphering the evolutionary history of other genes that are involved in enamel formation," said Mark Springer, team leader. Springer collaborated with colleagues based at the University of California, Riverside, Texas A&M University, and the San Diego Zoo's Institute for Conservation Research.

Financial Disclosure: This work was supported in part by the National Science Foundation (EF06298660 to MSS and JG, DEB-0743724 to JG, and EF0629849 to WJM. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Citation: "Molecular Decay of the Tooth Gene Enamelin (ENAM) Mirrors the Loss of Enamel in the Fossil Record of Placental Mammals."
Meredith RW, Gatesy J, Murphy WJ, Ryder OA, Springer MS (2009)
PLoS Genet 5(9): e1000634. doi:10.1371/journal.pgen.1000634

Source
PLoS Genetics