Anthropologists routinely use tooth form to study the phylogeny, masticatory function, behavior and diet of living and extinct primates. Recently, anthropologists have begun hypothesizing how candidate genes involved in tooth development relate to dental traits in primates. These candidate genes are hypothesized to be involved in determining tooth type and influencing cusp form. All of these candidate genes, however, are based on developmental studies of mouse teeth. Unfortunately, mice have highly derived dentitions that are dissimilar to primates and most other mammals. This project will begin to address this shortcoming by being the first to describe gene expression patterns during tooth development in pigs - a mammal with a generalized dentition more similar to primates. Pigs are a significant improvement as a model for studies of primates because, like primates, they have incisors, canines, premolars and molars as well as tooth replacement. This project will also build on the extensive use of pigs as models in studying primate bone and dental biology. Three specific aims will be addressed in detailing the genetic mechanisms of tooth development in pigs. First, this research will describe molecular patterns of gene expression involved in establishing tooth type in pigs. Most importantly, this will be the first study identifying gene expression patterns related to the development of canines and premolars. Second, the proposed research will determine how gene expression patterns relate to cusp placement and number. Third, this work will determine if similar gene expression patterns are observed during permanent tooth development as seen during deciduous tooth development. All hypotheses linking dental development to tooth form are currently based on the deciduous teeth, while most analyses on primate dental morphology are on permanent teeth. As the first study detailing gene expression during tooth development in a generalized mammalian model similar to primates, biological anthropology will benefit from being able to formulate more informed hypotheses linking primate dental form to developmental genetic pathways. For example, an improved understanding of the genes that contribute to forming each of the four tooth types found in primates can be useful for biological anthropologists hypothesizing why certain primate groups, such as the group including humans, have lost teeth during their evolution. Biological anthropologist can use the results of this work to identify dental character correlations for phylogenetic studies, to evaluate possible genetic pathways underlying primate dental evolution, and to help decipher developmental constraints on the evolution of primate tooth form. Furthermore, results from studying pigs can be applied to research on a wide range of mammals. Finally, the novelty of this research will help bridge a gap between developmental biology and biological anthropology. Broader impacts from this work include training of a female graduate student in several areas of biological anthropology and developmental biology. Society may benefit from the basic science data on dental development collected here through its application to clinical studies of dental genetics. Pictures of stained embryos will be placed on a database website (www.neoucom.edu/dldd) and made freely available to the public for research and educational purposes.
