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Genetic comparisons yield insight into the evolution of enamel thickness during human evolution
Julie E Horvath1, Gowri L Ramachandran2, Olivier Fedrigo3
1North Carolina Museum of Natural Sciences, Nature Research Center, Raleigh, NC 27601, USA; Department of Biology, North Carolina Central University, Durham, NC 27707, USA; Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA; Duke Institute for Genome Sciences and Policy, Duke University, Durham, NC 27708, USA.
Journal of Human Evolution
|May 10, 2014
Summary
Investigating gene regulation reveals that non-coding DNA changes, not protein mutations, likely drove the evolution of thick enamel in humans and chimpanzees. These genetic shifts in enamel genes offer insights into hominoid evolution.
Area of Science:
- Evolutionary biology
- Genetics
- Paleoanthropology
Background:
- Enamel thickness in hominoids is crucial for understanding diet, life history, and evolutionary relationships.
- Human enamel formation is linked to mutations in genes for enamel matrix proteins and proteases.
- Previous studies indicated positive selection in the MMP20 gene's regulatory region in humans and chimpanzees.
Purpose of the Study:
- To investigate evidence of positive selection in the regulatory regions (5' and 3' flanks) of key enamel genes (AMELX, AMBN, ENAM, MMP20).
- To compare human sequence changes with other hominoids and a rhesus macaque outgroup to understand enamel thickness evolution.
- To identify potential regulatory elements and transcription factor binding sites involved in enamel development and evolution.
Main Methods:
- Comparative genomic analysis of enamel-related genes (AMELX, AMBN, ENAM, MMP20) across hominoids and rhesus macaques.
- Examination of both protein-coding regions and cis-regulatory regions (5' and 3' flanks) for signs of positive selection.
- Identification of species-specific nucleotide sites and potential transcription factor binding sites within regulatory regions.
Main Results:
- No evidence of positive selection was found in the protein-coding regions of the studied genes.
- Strong evidence for positive selection was detected in the 5' flank of MMP20 and ENAM in the human lineage.
- The 5' and 3' flank regions of MMP20 showed strong evidence of positive selection along the chimpanzee lineage.
- Putative transcription factor binding sites were identified in regulatory regions with species-specific nucleotide changes.
Conclusions:
- Evolution of enamel thickness in hominoids is likely driven by changes in gene regulation rather than alterations in protein sequences.
- Non-coding variations in regulatory regions of enamel genes (MMP20, ENAM) play a significant role in the rapid evolutionary changes of enamel thickness.
- These findings provide insights into the genetic mechanisms underlying the enamel phenotype and hominoid evolutionary adaptations.
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