A recent study shows Zebrafish are helping U researchers to understand hearing and balance in the human ear.

By using the transparent fish, scientists can identify gene defects that lead to abnormalities like deafness.

“In vertebrate model organisms, we can determine when, during development, things start to go wrong and which cells are primarily affected,” said Tatjana Piotrowski, assistant professor of neurobiology and anatomy. “Such knowledge is necessary if, in the future, we want to prevent or treat diseases, such as deafness.”

By studying fish, scientists figure out how glial cells talk to nerve cells to form a functional ear.

Glial cells may be essential for the normal development of nerve cells, which are responsible for hearing and balance, according to the study published in the Jan. 6 issue of Neuron magazine.

“Using zebrafish as a model, we’ve demonstrated that glial cells play a previously unidentified role in regulating the development of sensory hair cell precursors-the specialized neurons found in the inner ear of humans that make hearing possible. This research increases our understanding of how nerve cells develop and whether it may be possible to regenerate these types of cells in humans one day,” Pirotrowski said.

Scientists believe that glial cells, or glia, are essential for healthy nerve cells. However, in the last 10 years, scientists have learned that glia aren’t just “glue” holding nerve cells together. Glias communicate with each other and even influence communication between neurons.

Piotrowski’s research in zebrafish focuses on the development of sensory neurons known as hair cells. Like humans, zebrafish use hair cells to detect sound and motion. However, in humans hair cells are buried deep inside the inner ear, making them difficult to access. Hair cells in zebrafish are located on the body surface and help fish swim in groups and avoid predators.

“The hair cells are exposed and can be easily seen under the microscope in the live fish. We can also visually identify the consequences of gene defects in the 200 to 300 embryos each female fish produces,” she said.

By studying these mutant embryos, Piotrowski and her colleagues discovered that during development the zebrafish is “seeded” with future hair cells. These precursor cells eventually go on to make hair cells, but only when they are sufficiently far enough away from the glial-ensheathed nerve.

“We know something in the glia is regulating development and acting as an inhibitory cue. It’s possible that this signal could also play a role in the development of stem cells throughout the nervous system. Much more research is needed to identify this signal but we’re optimistic our work has set the stage for future discoveries,” Piotrowski said.

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