Exome Sequencing Reveals Mutation Associated with Hearing Impairment

Researchers have used the power of next-generation sequencing to identify a gene involved in hearing impairment in a mouse study. The findings reveal a new and unexpected function for a previously well-studied gene. The study, published on September 21, 2011 in Genome Biology, found that this mutation is involved in otitis media, an inflammation of the middle ear, which is a prominent cause of hearing impairment especially in children. This research highlights the power of genome sequencing to identify causative mutations. "Otitis media is the leading cause of surgery in children in the developed world. It affects 35% of children under the age of 2 in Europe," explains Dr. Jennifer Hilton, from the Wellcome Trust Sanger Institute and first author on the paper. "With these expanding developments in the genetics and the understanding of otitis media, there is a possibility of reducing the need for invasive surgery in young children in the future." This research emphasizes two important concepts. Firstly, exome sequencing can detect mutations that increase the chances of developing a disease but don't necessarily cause the problem in every person carrying the mutation (a phenomenon known as reduced penetrance). Secondly, the middle ear disease was detected only because the researchers looked for it, and could easily be missed in a mouse, suggesting that we only find what we look for in mouse models of disease. The team studied the exome sequence of one affected mouse and found a mutation in the Islet1 gene. They then looked for this mutation in a collection of affected mice and found that all contained the mutation in the Islet1 gene. The mutants show a thickened and inflamed lining of the middle ear and excessive fluid and cell debris in what should be an air-filled middle ear cavity, which is a clear indication of chronic otitis media.
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