The Evo-Devo of Vertebrate Teeth & Jaws

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Eating is essential to survival. Animal head size and shape is heavily influenced by the types of foods animals eat. A core question driving studies of vertebrate evolution is how animal heads diversified without compromising vital functions and parts, including teeth and the jaws that hold them. To eat and survive to raise offspring, an animal's teeth and jaws must develop properly in the right place, at the right time. Despite keen scientific and public interest in teeth and faces, the developmental-genetic processes that coordinate tooth and jaw growth remain mysterious. Explaining these processes is vital to understand how species develop, evolve, and adapt to eat a variety of foods. In some species, including humans, teeth and jaws are also important for communication, such as making sounds and facial expressions. Also, human tooth and jaw evolution is likely entwined with our cultural evolution, notably tool use and cooking. The long-term vision of my NSERC-funded research program is to reveal the extent to which dental and jaw tissues influence each other's development and evolution (evo-devo) and, in this way, help explain the vivid, varied faces and diets of prehistoric and living species. Our wedge into this persistent question was to study toothless mice missing the expression of a gene, p63. My trainees and I discovered a network of genes controlled by p63 incidental to mandible formation but required for tooth development that we think allows teeth to evolve without forcing the jaw skeleton to change. We have strong evidence that this gene network controls tooth development in mice, monkeys, and fish. Our next step is to study where, how, and why these genes act in the teeth of these three animal groups. We will collect data from mice to test which genes in the network speak to each other directly, and define the links of this network. To reveal what these genes do in mice, we will experimentally block each gene's activity in the developing tooth. In fish, we will test if this gene network acts in teeth within the mouth only or also teeth within the throat. In parallel, we will define where these genes act in the teeth of monkey species, including some more closely related to humans. Our new knowledge about how these genes work together, what they do, and where during tooth development will not only advance our research aims and vision but will also be valuable more broadly to biologists, ecologists, anthropologists, as well as dentists. My team combines developmental genetics, 3D imaging, statistical shape and anatomical analyses of hard and soft head tissues to define and model the factors that constrain, or facilitate, morphological evolution of the toothed jaw including in human ancestors. My inclusive lab culture champions equity and diversity. Trainees accrue a host of in-demand professional skillsets, making them competitive for jobs in natural science and engineering research, and in education, industry, and policy.