Fish research at Washington State University could help scientists better understand some developmental disorders that cause facial deformities.
Jim Cooper, a WSU Tri-Cities assistant professor of biological sciences, studies “jaw protrusion,” a biomechanical ability shared by many fish. For a fish, pushing its jaw out allows it to more easily catch prey, and is an evolutionary advantage comparable with the ability of most birds to fly, Cooper said. The difference is, there’s about twice as many fish with the ability as there are living bird species.
“If you’re talking about biomechanical abilities that have been useful in terms of promoting diversification of lots of species, jaw protrusion is a champ,” he said.
Studying that ability can also increase the understanding of skull growth during development. And not just for fish, but for humans as well.
Jaw protrusion seems tied to the presence of thyroid hormone, appearing when the fish are nearly full-grown and are hit by a surge of the hormone.
“(It) suggested to us that it’s actually the thyroid hormone that they needed to develop that protrusion,” said Demi Galindo, a graduate student who works with Cooper.
When thyroid hormone decreases, she said, the fish lose the ability to protrude their jaws.
Human skull development is also affected by thyroid hormone, Cooper said. People who lack iodine, which is essential to the hormone’s production, or face other barriers to production often have facial abnormalities.
In people, the link between thyroid hormone and skull development could help explain certain developmental disorders like Crouzon’s syndrome, which is characterized by abnormal skull development.
There are two hormonal signals related to midface development that interest Cooper: thyroid hormone, which travel throughout the body, and another, known as fibroblast growth factor, which only affects the midface area.
His hypothesis is that the thyroid hormone might affect the second, more localized signal.
Reduction in either of those signaling hormones results in very similar midface developmental abnormalities, he said. Either way, the result is the same.
Finding out how the thyroid hormone affects this localized signal might help scientists to create treatments in the future that could be administered early in human development so defects never occur, Galindo said.
“If you can figure out what thyroid hormone is doing to alter (craniofacial) changes, you may be able to one day create the protein and give it as a treatment with gene therapy,” she said.
But treatment is still a long way off, Cooper said, and the hypothesis is still a big “if.” The main goal is to increase knowledge of skull development, which will allow researchers to better understand skull diseases.
“Maybe you could develop a genetic screen,” he said. “At least the parents would be prepared.”