Specialists in the US have found a new type of genetic mutation responsible for deafness and hearing loss associated with Usher syndrome type 1, a defect that causes night-blindness and a loss of peripheral vision through the progressive degeneration of the retina.
Researchers at the University of Cincinnati (UC) and Cincinnati Children's Hospital Medical Center say that the findings, published in the online edition of the journal Nature Genetics, could help experts develop new treatment options targets for those at risk of the disease.
The study partners included experts at the National Institute on Deafness and other Communication Disorders (NIDCD), Baylor College of Medicine and the University of Kentucky, who were led by Dr Zubair Ahmed, assistant professor of ophthalmology, who conducts research at Cincinnati Children's. He commented: "We were able to pinpoint the gene which caused deafness in Usher syndrome type 1 as well as deafness that is not associated with the syndrome through the genetic analysis of 57 humans from Pakistan and Turkey."
The expert explained that a protein known as CIB2, which binds to calcium within a cell, is associated with deafness in Usher syndrome type 1 and non-syndromic hearing loss. "To date, mutations affecting CIB2 are the most common and prevalent genetic cause of non-syndromic hearing loss in Pakistan. However, we have also found another mutation of the protein that contributes to deafness in Turkish populations," Dr Ahmed added.
Dr Saima Riazuddin, assistant professor in UC's department of otolaryngology who conducts research at Cincinnati Children's and was co-lead investigator on the study, explained that in animal models, CIB2 is found in the mechanosensory stereocilia of the inner ear - or hair cells - which respond to fluid motion and allow hearing and balance, and in retinal photoreceptor cells, which convert light into electrical signals in the eye, making it possible to see.
The specialists found that CIB2 staining is often brighter at shorter row stereocilia tips than the neighbouring stereocilia of a longer row, where it may be involved in calcium signaling that regulates mechano-electrical transduction, a process by which the ear converts mechanical energy - or energy of motion - into a form of energy that the brain can recognise as sound.
Dr Ahmed added: "With this knowledge, we are one step closer to understanding the mechanism of mechano-electrical transduction and possibly finding a genetic target to prevent non-syndromic deafness as well as that associated with Usher syndrome type 1."