Sharks and people have the same teeth-growing cells
People have the same cells that allow sharks to keep growing new teeth, according to a new study.
Scientists have known for some time that some fish, such as sharks and rays, develop rows of highly specialized teeth with the capacity for lifelong regeneration. However the genetic mechanisms that enable this to happen were poorly understood.
Now researchers, led by Gareth Fraser from the University of Sheffield’s animal and plant sciences department, have identified how a special set of epithelial cells, called the dental lamina, are responsible for the lifelong tooth regeneration in sharks.
Humans also possess this set of cells, which facilitate the production of replacement teeth, but only two sets are formed—baby and adult teeth—before this set of specialized cells is lost.
The team identified a network of genes that allow sharks to replace rows of their teeth using a conveyer belt-like system.
These tooth-making genes in sharks are conserved through 450 million years of evolution, and probably made the first vertebrate teeth. These “tooth” genes, therefore make all vertebrate teeth from sharks to mammals—however, in mammals, the tooth regeneration ability that utilizes these genes has been highly reduced over time.
“We know that sharks are fearsome predators and one of the main reasons they are so successful at hunting prey is because of their rows of backward pointing, razor-sharp teeth that regenerate rapidly throughout their lifetime, and so are replaced before decay,” says Fraser.
By analyzing the teeth of catshark embryos, Fraser’s team characterized the expression of genes during stages of early shark tooth formation. They found that these genes participate in the initial emergence of shark’s teeth and are re-deployed for further tooth regeneration.
The study suggests that at the beginning of the sharks’ evolutionary history, their teeth were most likely continuously regenerated and used a core set of genes from members of key developmental signaling pathways, which were instrumental in sharks evolving to maintain the ability to re-deploy the genes to replace teeth when needed.
The Natural Environment Research Council and the Leverhulme Trust funded the study, which appears in the journal Developmental Biology.
Source: University of Sheffield