Investigating the process of hearing

21 November 2008

The 2nd Deafness Research UK UCL Ear Institute Fellowship was awarded to Dr Joerg Albert, who joined the Institute from the University of Cologne.

[Fellowship: 2008-2011]

Dr Albert is studying Drosophila melanogaster (the fruit fly) to help answer a fundamental question in hearing: how do sound waves – cyclic changes in air pressure – get turned into electrical signals that the brain can interpret?

Although some parts of the task are understood, little is known about the protein building blocks that form a key type of ‘channel’ through the membrane of sensory cells in the inner ear. These channels are opened and closed mechanically in the last stage of a process that begins with the eardrum vibrating in response to sound waves.

Vibrations in the eardrum move bones in the middle ear like a lever, passing the motion on to the inner ear, which is filled with fluid. The motion creates waves in the fluid which cause a membrane in the inner ear to ripple at the frequency of the vibration.

Sitting on the membrane are the hair cells. These get their name from tiny hair-like elements called stereocilia that project from the tip of each cell. As the membrane ripples, the stereocilia sway back and forth, pulling open and pushing shut the channels like a gate.

When the channels are open, electrically-charged molecules called ions flow from the fluid in the cochlea into the hair cell. This process is called mechano-transduction and is the point at which mechanical energy gets transformed into an electrical signal.

Dr Albert is using a number of techniques to study the function of an ion channel known as NompC. His aim is to discover whether NompC forms mechano-transducer channels in the fruit fly.

“Fruit flies and humans share a common evolutionary history which is, for example, still reflected by a considerable overlap of the molecular machineries that orchestrate the development of their ears”, says Dr Albert.

Recently published research by Dr Albert and his former colleagues in Cologne has shown that mechano-transduction is similar in fruit flies and humans. However, fruit flies are much simpler to study. Identifying the transducer channel and studying it in a simple working system therefore has the potential to significantly advance our understanding of how the auditory system works. This knowledge may ultimately lead to new genetic or pharmaceutical treatments for hearing loss.