The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


Enamel thickness in Microcebus murinus and Macaca mulatta and the evolutionary genetics of enamel matrix proteins in hominoids

JULIE E. HORVATH1,2, CHRISTINE WU1, MAXX TOLER1, OLIVIER FEDRIGO2,3, LISA W. PFEFFERLE2,3, ANTHONY MOORE2,3, GOWRI L. RAMACHANDRAN1, COURTNEY C. BABBITT2,3, JUKKA JERNVALL4, GREGORY A. WRAY1,2,3 and CHRISTINE E. WALL1.

1Department of Evolutionary Anthropology, Duke University, 2Institute for Genome Sciences and Policy, Duke University, 3Department of Biology, Duke University, 4Institute for Biotechnology, University of Helsinki

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Thick molar enamel is a key feature in discussions of phylogeny, life history and dietary adaptation during human evolution. Recent genomic scans provide evidence of positive selection on the regulatory regions of many diet-related genes, including the enamel matrix proteinase MMP20 (Haygood et al. 2007). Our long-term goal is to document links between genomic evolution and traits related to dietary changes during human evolution. One focus of this work is to sequence eight genes known to have a direct effect on enamel secretion and maturation, and to determine whether there is evidence for positive selection on the regulatory regions of these genes in hominoids. Preliminary data on four functionally-related genes (MMP20, KLK4, AMELX, and AMELY) in Homo, Pan, Gorilla, Pongo, and Hylobates provide insights into the evolutionary history of major components of enamel development and structure. To expand these studies, here we report average (AET) and relative (RET) enamel thickness for the molars of Microcebus murinus and Macaca mulatta, species that serve as phylogenetic outgroups in the genomic analyses. AET and RET (Smith et al. 2003) are measured from high-resolution microCT scans using Avizo and ImageJ.

In M. murinus, the enamel is thin: mean AET=0.03mm, s=.007; mean RET=7.8, s=2.3 (n=3 individuals, 9 molars with moderate wear). In M. mulatta, the enamel is intermediate: mean AET=0.32mm, s=0.027; mean RET=14.7, s=1.6 (n=5 individuals, 7 unworn molars). These contrasting enamel thickness values provide a good basis to identify selection on genes implicated in regulating enamel formation.

This study was funded by NSF-BCS-08-27552 HOMIND, the Wenner-Gren Foundation for Anthropological Research, the Duke Primate Genomics Initiative, and the Howard Hughes Undergraduate Programs.

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