Audiology in Brief The human body has roughly 20,000–25,000 genes, and for the most part, each gene is believed to be responsible for encoding one particular protein. However, researchers have found a gene that causes human deafness that can multi-task and make two completely different proteins. Although there have been a few ... News in Brief
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News in Brief  |   January 01, 2009
Audiology in Brief
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Hearing Disorders / Special Populations / Genetic & Congenital Disorders / News in Brief
News in Brief   |   January 01, 2009
Audiology in Brief
The ASHA Leader, January 2009, Vol. 14, 5. doi:10.1044/leader.NIB.14012009.5
The ASHA Leader, January 2009, Vol. 14, 5. doi:10.1044/leader.NIB.14012009.5
Deafness Gene Encodes Two Proteins
The human body has roughly 20,000–25,000 genes, and for the most part, each gene is believed to be responsible for encoding one particular protein.
However, researchers have found a gene that causes human deafness that can multi-task and make two completely different proteins. Although there have been a few other examples in which one gene can make two different proteins, this example is the first in which mutations in a fusion gene cause a disorder that exhibits a simple pattern of inheritance.
The gene, called LRTOMT, is a fused version of two separate genes that appear in mice and rats: Lrrc51 and Tomt, according to a study published in the November 2008 issue of Nature Genetics.
Geneticists Zubair Ahmed and Thomas Friedman, together with scientists from the Centre of Biotechnology of Sfax (Tunisia) and Radboud University in The Netherlands, used molecular biology techniques to identify a gene on chromosome 11 that is responsible for nonsyndromic deafness. The researchers were able to pinpoint the gene from a larger region (DFNB63) that had been found to be associated with nonsyndromic deafness.
Until now, the gene responsible for DFNB63 deafness in humans was a scientific puzzle. The researchers found that although the neighboring Lrrc51 and Tomt genes in mice each make separate proteins, in humans, the fused version of these genes also makes two separate proteins (LRTOMT1 and LRTOMT2). The researchers also identified four mutations that resulted in deafness in families they studied. All of the mutations primarily affect the LRTOMT2 protein. The next goal is to study the function of LRTOMT and determine how mutations of this gene cause deafness in humans.
Mutation Linked to Progressive Hearing Loss
European researchers have identified a mutation in mice that mimics progressive hearing loss in humans.
A research team from the Wellcome Trust Sanger Institute (Cambridge, England) in collaboration with colleagues in Munich, Germany, and Padua, Italy, found that mice with a mutation in a gene called Oblivion had problems with inner-ear hair-cell function. Mice with one mutant copy of Oblivion showed initial cochlear hair cell function, which later degenerated. Mice with two mutant copies of the gene showed congenital damage to cochlear hair cells.
“When we mapped the mutation to the mouse genome, we quickly found a probable cause for hearing loss,” said lead author Karen Steel in a news release. “We showed that the mutant mice carried a change in one letter of their genetic code in a gene called Atp2b2. Changing a specific C to a T in this gene stops it from producing a normal molecular pump that is needed to keep hair cells in the ear working efficiently by pumping excess calcium out of the cell.”
The Oblivion mutation is unique in the way it causes hearing loss due to mutations in Atp2b2, a gene previously linked to human hearing loss. The study was published Oct. 31 in the open-access online journal PLoS Genetics.
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January 2009
Volume 14, Issue 1