Making Waves: From Pattern to Structure in Dental Evolution

Dental patterning-the number, location, and morphology of teeth in the jaws-has been a major factor in primate and human adaptive radiation. The specializations made possible by dental variation are among the diagnostic characteristics of primate and hominid evolution, and teeth are among the most important evidence preserved in the fossil record. The dentition can be viewed as a set of nested 'waves' of growth along the embryonic dental lamina. The wave-peaks first determine the position of teeth along the jaws. Subsequent peaks sculpt the cusps within teeth, and the results are fixed in place by mineralization. This wavelike pattern is generated by quantitative interactions among diffusible (extracellular) signaling factors. The first objective of this project is to use transgenic mice with altered expression levels of these factors, to see whether variation resembling that occurring naturally can be produced. By making and then interbreeding animals with enhanced and reduced expression of these signaling factors, a better understanding of how the patterning process actually works.

Second, not all genes involved in dental patterning are yet known. Gene mapping methods will be applied to data on dental variation in a large baboon genealogy at the Southwest Foundation for Biomedical Research in San Antonio, data collected by colleagues in Texas and at the University of Illinois. Similarly, gene mapping will be done in commercially available recombinant inbred laboratory mice, in which variation similar to that observed in the baboons has been found. Chromosomal regions that may carry genes affecting dental patterning will be explored by gene-expression studies and bioinformatic (computer-based) methods to identify those genes, determine how their expression is regulated, and characterize their appearance in developing teeth in embryonic mice.

This broader impact of this project will extend well beyond anthropology, to biology in general, because one of the most fundamental questions of all of life, plant, animal and human is: How do complex patterns of which organisms are built come about? The dentition can serve as a model for many similar processes across the spectrum of life. Technical materials like DNA clones and the sequence data will be made available to the research community, and the results will be made accessible to the scientific and general public through various review and overview articles. The laboratory routinely includes undergraduates and minorities, as well as national and international collaborations. This work is routinely included in courses taught, and NSF REU supplements often support undergraduates in the laboratory.