Understanding human nerve cell development - Zebrafish may hold key

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Understanding human nerve cell development - Zebrafish may hold key

Traditionally viewed as supporting actors, cells known as glia may be essential

for the normal development of nerve cells responsible for hearing and balance,

according to new University of Utah research. The study is reported in the

January 6, 2005 issue of Neuron and is co-authored by scientists at the

University of Washington.

" 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, " said Tatjana Piotrowski, Ph.D., assistant professor of

neurobiology and anatomy at the University of Utah School of Medicine.

Scientists long have known that glial cells, or simply 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. Glia communicate with each

other and even influence synapse formation 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

surface of their body and help the fish swim in groups and avoid predators.

" Zebrafish are a wonderful model for studying hair cell development for a number

of reasons. 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 through a

process known as placode migration. These precursor cells, called interneuromast

cells, eventually go on to make hair cells, but only when they are sufficiently

far enough away from the glial-ensheathed nerve.

" Once these cells are far enough away from the glia they begin to differentiate

into hair cells. 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, " said Piotrowski.

The University of Utah has one of the largest zebrafish facilities in the

country with more than 6,000 zebrafish tanks. In addition to Piotrowski, six

other University faculty members use the fish to study various clinical

disorders including leukemia, colon cancer, congenital heart defects, muscular

dystrophy and other birth defects.

NOTE: Video of zebrafish larva being " seeded " during placode migration with

neuromast precursors is available through Dr. Piotrowski. For a sample of what

the images look like, visit www.neuro.utah.edu and click on Dr. Piotrowski's

home page (listed under the faculty link).