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Genetics and pathobiology of deafness

It is estimated that over 250 million people worldwide suffer moderate to profound hearing loss, of which half have a genetic basis. The process of hearing, the acquisition and transduction of sound from the ear to the auditory cortex, is immensely complex, and this complexity is reflected in the genetic repertoire that is responsible for its development and function. We study various aspects of this repertoire to advance our knowledge of deafness and improve treatments.

Deafness can occur early in life, with around 1 in 1000 children affected. This can result in delayed development of speech, language and cognitive skills, and may lead to slow learning and difficulty progressing in school. In addition, hearing loss can manifest as a late-onset condition called presbycusis, with an estimated 25% of people aged 65-75 and 70-80% of people over age 75 suffering from hearing impairment, which has psychological, physical and social consequences.

The deafness group continues to make very significant advances in understanding the development, transduction and homeostasis of the auditory system. Using various mutagenesis screens, we utilise the similarities between the mouse and human genomes, and between the physiology and anatomy of their auditory systems, to discover and investigate genes involved in two major types of hearing impairment - sensorineural hearing loss and otitis media.

Sensorineural hearing loss

An impairment resulting from dysfunction in the inner ear, auditory nerve, or auditory cortex of the brain. The majority of sensorineural deafness is associated with abnormalities in hair cells found within the organ of Corti in the cochlea, which convert sound vibrations into neural signals.

Otitis media (OM)

Chronic otitis media, sometimes known as ‘glue ear’, is an inflammatory condition of the middle ear that occurs in childhood, where the middle ear fills with glue-like fluid, leading to conductive hearing loss. We also study the mechanisms by which the middle ear is infected by bacteria that cause acute otitis media.

To date, around 130 loci that cause non-syndromic hearing impairment have been mapped in the human genome (http://hereditaryhearingloss.org/). However, the genes underlying nearly half of these loci have yet to be identified, so we are still far from determining a complete picture of the genetic networks underlying the auditory system. We have uncovered several of the genes involved in OM, but more remain to be uncovered.

Anatomy of a mammalian ear.

Adapted from: Brown, S. et al. (2008) Nature Reviews Genetics. 9:277-290