What Are Genetic Deafness? Hearing is one of the basic elements of human communication, yet millions of Americans are hearing impaired. Currently only a few strategies for overcoming the deficiency exist. For example, some people with a moderate case can overcome the impairment with hearing aids, which amplify sounds. Others bypass the communication setback with sign language. Researchers now hope that new findings on the genetic component of deafness will help expand treatment options. Painstaking analysis has led to the recent discovery of a large number of mutated genes that are involved in causing deafness in humans. An understanding of how these genes operate is helping researchers devise biological strategies to protect or restore human hearing.
But what if the silence was endless?
Many individuals spend life unable to detect nagging yells as well as romantic whispers, telephone chit chat and radio tunes because their hearing system is damaged. In fact, about 30 million Americans have moderate to severe hearing impairments.
Sometimes the impairment is triggered by an outside source. Toxic drugs, infections or booming noises louder than 90 decibels like a jet engine roar can injure a hearing system. But researchers also are finding definitive evidence that defective genes are common culprits.
Passed along from our parents, genes hold important data. The information guides the production of proteins, which run our development and function. Recently, scientists identified a heap of altered genes that impair the hearing system and instill deafness.
Years ago, examinations of family trees yielded the first clues of a genetic component in deafness. One old research document notes that a 16th century aristocratic family passed on deafness through three generations.
technologies advanced in the later part of this century, researchers began to scrutinize the genetic make-up of these families plagued with deafness. In recent years, they identified more than a dozen mutated genes that lead to a typical form of deafness, known as nonsyndromic hearing loss, which includes no other symptoms. For example, the analysis of a large family in Costa Rica with deaf members dating back as far as the 1700s led to the identification of one of the first human deafness genes in 1997. This gene is involved with deafness that evolves later in life. So far, however, it’s only been found in the one family. Another discovered gene, which keeps popping up in many different unrelated families with deaf members, is linked to childhood deafness.
Quirky mice also are helping researchers track down deafness genes. The animals, which acquired titles such as “shaker” and “waltzer” because of their circling and staggering gait, are born profoundly deaf. Researchers identified genes that cause their deafness and later discovered that some hearing-impaired humans carry alterations in some of the same genes. Currently researchers are trying to develop a vehicle to deliver healthy versions of the genes to the mice after birth to restore hearing. If successful, a similar strategy may restore hearing in humans.