FRIDAY, Aug. 30, 2002 (HealthDayNews) -- Scientists have identified yet another deafness gene, and they say their discovery should one day help solve the puzzle of hearing loss and lead to a screening test and treatment.
The newly discovered gene brings to 26 the number of genes known to play a role in deafness. However, how the scientists arrived at the discovery of the latest gene is novel.
First, a team from the University of Michigan identified the gene in mice, naming it the Tmie gene for transmembrane inner ear, which is the location of the protein encoded by the gene.
"Either the protein is not made [in the case of hearing loss], or it's made but is faulty," explains David Kohrman, an assistant professor of otolaryngology and human genetics at the University of Michigan who discovered the Tmie gene.
Next, he shared the information with a team from the University of Iowa and the National Institutes of Health, which had been studying families with inherited hearing loss. They had located the general area of the gene in these families, but information from the mouse research helped them zero in on the human gene, which they named TMIE.
The findings appear in the September issue of the American Journal of Human Genetics and the August issue of Human Molecular Genetics.
"Defects in lots of different genes cause deafness," says Kohrman, lead author of the Human Molecular Genetics paper. "That's not surprising, based on the fact that the inner ear is a complicated organ with many different cell types."
The new gene is thought to play a role in the normal functioning of the ear's sensory hair cells, which help convert external sounds to electrical impulses that can be transmitted to the brain and interpreted as sounds.
About one in 1,000 infants has a profound hearing impairment, according to the National Institutes of Health. Half of the cases are believed to be genetic in origin.
"Dr. Kohrman and his colleagues did a great job," says Neil Segil, a scientist at the House Ear Institute, a research and treatment facility in Los Angeles. "It's exactly the kind of synergy that can be expected when we invest in animal research, and coordinate it with human research. We can't do this kind of research in humans [that was done in mice to find the gene]."
"The biggest question that is still outstanding is exactly how prevalent this mutation, or defective gene, is," Segil says.
A gene discovered in 1997, called connexin 26, is believed to be responsible for about half the inherited hearing-loss cases.
"There is always some hope that as each new mutation is identified, it will represent a larger portion," Segil says. Eventually, he adds, treatments will be tailored to the genes involved in the particular case of hearing loss.
"There are probably over 100 genes that when mutations occur can cause deafness," Segil says.
The newly discovered gene is not the most common hearing-loss gene, says Ed Wilcox, a staff scientist at the National Institute on Deafness and Other Communication Disorders, part of the National Institutes of Health. He's also co-author of the paper in the American Journal of Human Genetics.
"But it is certainly not a rare gene either," he says. "It is going to contribute to the genetics of hearing loss."
Next, Kohrman plans to look more closely at the faulty gene, to see what goes wrong on the cellular level. Eventually, gene therapy may help correct the defect, he says.
What To Do
For more information on hearing loss, see the Deafness Research Foundation. For information on communication options for children who are deaf or hard of hearing, visit the National Institute on Deafness and Other Communication Disorders.
