Jawed vertebrates evolved from jawless fish a half billion years ago. This project aims to elucidate the developmental and genetic bases of this major evolutionary transition using the jawless fish lamprey as a model for the first jawless vertebrates. To do this, lamprey embryos will be injected with reagents to block or enhance the function of several genes involved in head skeleton development. These manipulations are aimed at partially recapitulating the evolutionary process and will reveal if changes in the function or deployment of these genes drove the evolution of the jaw. In addition to shedding light on a major evolutionary event, the project will also provide insight into how the head skeleton and jaw develops in all vertebrates, including humans. This will contribute to ongoing efforts to understand the developmental and genetic basis of diseases affecting the face, skull, and jaw. The project will also provide training and support for a laboratory technician, graduate student, and undergraduate students, as well as an opportunity for high school volunteers to participate in basic biological research.
The jaw gave early vertebrates the ability to capture and process large prey, allowing them to spread across the planet and eventually give rise to our own species. The origin of the jaw was thus a critical event in the evolutionary history of modern vertebrates, including humans. The goal of the project was to elucidate the developmental and genetic bases of this major evolutionary transition using the jawless fish lamprey as a model for the first jawless vertebrates. To do this we determined how several dozen genes were turned on and off in the developing head of lamprey embryos and compared this with gene expression in the heads of jawed vertebrate embryos. To our surprise, we found that the basic genetic framework for building the jaw and skull is present in lamprey embryos, and by extension, was present in the very first vertebrates. This suggests that the evolution of the jaw involved changes to a relatively small number of genes, and that the diverse jaws and skulls of modern vertebrates are built upon a common plan. These findings were published in a series of 5 articles in peer-reviewed journals, with a follow-up article currently in preparation. The results were also disseminated through several talks at university seminars and conferences in the United States and internationally. Importantly, the project also supported hands-on research experiences and training for a dozen undergraduates and 5 high school students in a fully equipped, modern biology laboratory. It also provided training and summer stipends for 2 graduate students, and part time salary and benefits for a professional research technician. The work has laid the foundation for future studies examining how the form and function of the vertebrate jaw and skull are encoded in DNA.
