Around one in 200 people in the UK will lose their hearing due to a condition called otosclerosis, where the tiny stirrup (stapes) bone in the middle ear becomes fixed in place because of overgrowth around the joint.
This means it can no longer move to transmit sound waves into the inner ear: this causes hearing loss.
People with otosclerosis typically begin to lose their hearing as young adults, in their late teens or 20s. Current treatments include hearing aids, which are not always very effective, or surgery to remove part of the stirrup bone and replace it with a prosthetic device. This improves hearing in most people, but it does not restore full normal hearing, and there are some risks associated with the operation.
About a quarter of people with otosclerosis have a strong family history of it, suggesting that it is inherited. Previous research has not found a genetic cause. But a new DNA-sequencing technique, called 'whole exome sequencing', has been used in four families with otosclerosis. And, excitingly, the researchers have successfully identified a gene involved in causing the condition; it's the first to be discovered.
In this study, Dr Dawson and Professor Saeed will use whole exome sequencing to investigate more families, to try to identify additional otosclerosis genes. And they have a second aim: to investigate how mutations in identified genes cause otosclerosis.
One of the ways they will do this is by analysing damaged stirrup bones removed from patients undergoing surgery for their otosclerosis. They also want to investigate whether the same genes can cause otosclerosis in people without a strong family history of the disease.
'Finding genes involved in otosclerosis will help us to understand this condition and the processes involved. We hope this could lead to the development of effective treatments.'
By identifying genes involved in otosclerosis, Sally, Shakeel and their team hope to better understand the processes causing it. This is the gateway to developing and testing drugs to treat – or prevent – the condition.
Identifying the genes will also inform genetic counselling (a service that provides support, information and advice about genetic conditions, conducted by healthcare professionals who've received training in the science of human genetics). And families in which the gene has been found can get diagnosed early. This is important: drug therapies given before the bone has become fixed (and hearing loss has developed) are likely to be far more effective.