A molecular basis for replacement tooth formation in reptiles

There are a great number of genetic diseases that affect tooth number in humans. Ectodermal dysplasia (ED), for instance, is characterized by a reduction in the overall number of teeth (i.e., hypodontia). In contrast, people with cleidocranial dysplasia (CCD) may form dozens more teeth than normal. In both disorders, only the secondary generation of teeth ('adult teeth') is affected, while baby teeth are largely unaffected. Since conventional mammalian lab models, such as the rat and mouse, form only a single generation of teeth during their lives, they can tell us little about the molecular cues controlling tooth replacement. For this reason, Dr. Gregory Handrigan has turned to an unusual animal model: reptiles. Like humans, reptiles form multiple generations of teeth throughout their lives. As part of the first research to directly address the molecular control of generational tooth formation, Dr. Handrigan is identifying genes from reptiles such as the python and bearded dragon that underlie their ability to continually form new teeth. Given the overwhelming similarity in tooth development between reptiles and mammals, these genes are likely to be performing comparable roles in humans. Handrigan’s research could then generate important knowledge about the molecular control of tooth number in human development as well as for diseases like ED and CCD. Ultimately, his findings may provide a foundation for strategies to regenerate lost teeth in humans.