Researchers find gene important for helping body maintain balance

March 24, 2003

A newly discovered gene in mice appears to play an important role in the development of otoconia, tiny structures that help the body maintain balance.

For the first time, researchers have found a gene in mice that appears to play an important role in the development of structures critical for maintaining balance, says new research funded by the NIDCD and published in the April 1, 2003, issue of Human Molecular Genetics (online March 24). The gene, named Otopetrin 1 (Otop 1), may be responsible for the development of otoconia, small particles in the inner ear that, as they move in response to gravity and linear motion, help the brain interpret the body's orientation in space. Mice serve as good genetic models for humans in such areas as balance and hearing because mutations found in certain genes in the mouse generally affect the same function in humans.

Otoconia are tiny calcium stones embedded in a gel-like substance that overlies hair cells in two organs of the inner ear: the utricle and saccule. When the mouse tilts its head, the otoconia glide downward with respect to gravity, causing tiny hairlike bundles on top of the hair cells to bend. This bending action sends a signal to the brain, informing it of the body's new position.

Researchers from Washington University Medical School, St. Louis, Mo., and the University of São Paulo, Brazil, discovered that Otopetrin 1 houses two recessive mutations affecting balance: the tilted (tlt) mutation and the mergulhador (mlh) mutation. Mice possessing two copies of either of these mutations lack otoconia and are unable to swim, among other characteristics. Unlike most other mutations that affect balance, these mutations do not affect hearing or other balance-related structures, which indicates that Otopetrin 1 is responsible for otoconial development alone. The finding could be useful in helping researchers determine if otoconia, which are sometimes destroyed by aging, certain medications, infections, and trauma, can someday be regenerated in individuals with balance problems.

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