WASHINGTON A "dancing mouse," once kept as a pet because of its odd habit of circling around and around, may offer insights into the genetic causes of deafness, researchers said on Monday.
Scientists said they had identified a genetic mutation that caused the mice to "dance" and also made them deaf.
They do not know if some deaf people have the same mutation, but hope it can help explain why one child in 1,000 is born deaf.
Deafness is associated with more than 100 different genetic mutations so far, but many more remain to be discovered.
The mutation shared by the mice interferes with their ability to produce a protein known as defensin, Northwestern University Medical School researcher James Bartles and colleagues report in the latest issue of the journal Cell.
The protein is produced in many cells, but most importantly in this case, it is found in the hair-like stereocilia of hair cells in the inner ear, which detect sound and motion and help control balance in the body.
"I would say this opens the door on another possibility that might account for deafness in humans," Bartles said in a telephone interview.
The mutation Bartles and colleagues found in the mouse causes hair cell degeneration, deafness and dysfunction of the vestibular, or balance, functions of the inner ear.
The mice, known officially as "Jerker" mice, are also hyperactive, run around in tight circles and toss their heads. "They are stone deaf. They spend an inordinate amount of their time going around in these tight circles, which is a very quirky type of behavior," he said.
Bartles thinks the vestibular hair cells in the mice send false signals to the brain, in effect telling the animal it is falling or circling in one direction when it really is not. To compensate, the mouse turns in the opposite direction.
He said it was surprising to find such a profound defect caused by a single-point mutation in a gene, meaning a change in just one letter of the genetic code.
"What is it that is so darned important about this protein that its absence causes cells to go haywire?" Bartles asked.
He said scientists had known about the mutation for 60 years they just did not know what gene, and which protein, were affected.
"This behavior was first reported in 1941," he said.
"A scientist had a dancing mouse brought to him by a woman who collected dancing mice for a hobby." The mice were bred and studied. Other, similar mice, known as "Shaker" mice, have already given scientists insights into deafness.
British scientists found that genetically mutated mice known as "Shaker-1" mice did not make normal amounts of a protein called myosin VIIA. They, too, were deaf and circled compulsively.
They found that people with a similar mutation have Usher syndrome type 1B, which causes children to be deaf and also to have balance problems. They also eventually become blind.
Finding the genetic defect that causes a disease does not offer an immediate cure or treatment, but does help scientists better understand the problem and helps them plan future research.
(Reuter)