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April 30, 2003

Mutant mice speak out for the deaf

From: Hindustan Times, India - Apr 30, 2003

Agence France-Presse
Paris, April 30

Experiments with a batch of engineered mice have thrown up exciting genetic clues about why humans often suffer from worsening deafness as they get older.

The evidence points to a rodent gene called Ink4d, which plays a role in sensory hair cells in the inner hear.

These cells are the magic behind the so-called Organ of Corti, a structure about four centimetres long that spirals along the cochlea and is the vital link in the ability of mammals to hear.

The organ is filled with fluid which moves in response to sound waves.

Thousands of cells with tiny hairs line the organ, and when they move in response to the fluid, they generate electrical signals that stimulate fibres in the auditory nerve which is connected to the brain. This is how we perceive sound.

The problem is that sensory hair cells do not regenerate once they have been lost: the cells carry on dividing until just after a child is born, and then the process abruptly stops.

So if the cells are damaged by loud noise or -- in some individuals -- when the cells die off in significant numbers in later life, the result is progressive hearing loss.

Why these cells do not regenerate may now be explained in part thanks to Ink4d, say researchers at the House Ear Institute in Los Angeles.

Following up evidence that Ink4d plays a role in preventing cells from dividing, the team created mice whose genetic code had been modified to lack this gene.

© Hindustan Times Ltd. 2002.