Under its Discovery Grants Program, the Natural Sciences and Engineering Research Council (NSERC) of Canada awarded Dr. Joy Richman $201,000 over five years to study the development of skull anatomy and tooth regeneration in reptiles and birds, and under its Research Tools and Instruments Grants Program, just over $57,000 to set up a reptile research facility.
“Reptiles and mammals share a common ancestor dating back more than 300-million years, but through evolution signifi cant specializations in the skull and teeth have arisen,” explains Richman, a developmental biologist and specialist in pediatric dentistry. For example, the palates of mammals and reptiles differ. Mammals always have closed palates that separate the oral and nasal cavities. In contrast, snakes, lizards and birds have open palates. Alligators, surprisingly, have a closed palate like mammals.
Richman’s goal is to determine how and when in development these differences arose. The research will examine early embryos of reptiles in order to identify the genes that correlate with subsequent jaw differences. The function of promising candidate genes will be studied further using chicken embryos.
There are also striking differences in the capacity of mammals and reptiles to replace teeth. Most snakes, lizards and crocodilians replace their teeth continuously throughout life (polyphyodonty), whereas most mammals, including humans, can only replace theirs once.
The Richman lab will investigate tooth replacement in longitudinal studies on adult leopard geckos. By taking wax bite impressions, the shedding of teeth along the jaw will be recorded, giving insights into the timing and pattern of tooth replacement. Moreover, the lab will test whether there are genetic cues that regulate tooth renewal. The role of the environment in development of replacement teeth will also be tested by removing teeth, injecting drugs next to the teeth or locally damaging the dental tissues. Follow-up experiments will analyze the fixed tissues for gene expression, presence of stem cells and the effects on cellular dynamics to determine why reptiles have retained the ability to renew their dentition.
In the future, the identification of key molecules that regulate tooth replacement will be applicable to bioengineering human teeth. In order to conduct these experiments, funding has been provided for a new reptile research facility, including equipment such as a fluorescence stereomicroscope, camera, scavenger for anaesthetic gases, tissue culture incubator and reptile egg incubator. The equipment will be shared between Richman’s lab in the Life Sciences Institute and the UBC Centre for Comparative Medicine.
Richman’s reptile research group is unique in Canada and the world. Their innovative studies on molecular evolution of the skull and teeth will provide insights into how animals have adapted to environmental changes. Results are of great interest to paleobiologists, developmental biologists and the broad scientific community.
For more information about Dr. Joy Richman, click here.