Gonad determination, the process by which an individual initiates development as a male or female, is controlled by many mechanisms. In mammals, including humans, genad determination is insensitive to environmental influences like temperature and external hormones, but instead is responsive to a dominant genetic switch on the Y chromosome, such that individuals with a Y become males and those without a Y become females. Other vertebrates such as alligators and many turtles, are sensitive to non-genetic influences such as egg incubation temperature. In these species, no genetic determinant of gonads is known, and little is known about how temperature or other environmental signals influence gonad determination. The goal of this project is to identify common principles that govern gonad determination across vertebrate species. Using methods developed with mice, experiments will be carried out to determine the sequential gene expression events induced by temperature that initiate male and female development in turtles, and to identify the similarities and differences between turtles and mice. Preliminary results from incubating turtle eggs at the midpoint between male- and female-producing temperatures suggest that an additional underlying temperature-independent mechanism exists for determining gonads exists in turtles. This project will characterize this additional pathway, pinpoint when and how temperature influences the outcome, and provide large quantities of sequence and expression data valuable to this and other fields.
This work provides an outstanding opportunity for training in evolutionary and developmental biology for Duke graduate and undergraduate students, and visiting high school students from the North Carolina School for Science and Math. Special emphasis will be placed on introducing young students, including those from underrepresented groups, to field work during the summer turtle season. In addition, we plan to use this project to stimulate scientific literacy by engaging the public in conversations about basic science, the impact of the environment, and conservation via the Science Café in Durham.
