Investigating the process of hearing
The second Deafness Research UK / UCL Ear Institute Fellowship has been awarded to Dr Joerg Albert, who has come to the UK from his previous position as a post-doctoral research fellow at the University of Cologne.
Dr Albert will spend his three-year appointment investigating a fundamental element of sensory perception: the transformation of mechanical energy into an electrical signal that can be processed by a brain. This is called ‘mechano-transduction’ and occurs continually in the process of hearing.
Sound waves – cyclic changes in air pressure – cause the eardrum to vibrate. This in turn moves bones in the middle ear like a lever to pass the vibration on to the fluid-filled cochlea in the inner ear. Waves in the fluid cause a membrane, and the auditory ‘hair’ cells that sit upon it, to undulate at the frequencies present in the incoming sound waves. It is at this stage that the transduction takes place.
Hair cells are so-called because of the tiny hair-like processes named stereocilia that protrude from their tips. Stereocilia are connected to specialised transducer-channels in the hair cell membrane. When this membrane is in motion, the channels are pulled open and pushed closed like a gate by their connection to the stereocilia. An open channel means that electrically charged molecules – ions – present in the space outside the cell are free to flow inside. This gated flow of ions alternately increases and reduces the electrical signal passed on to later stages in the auditory system.
Little is known about the molecules which make up the transducer channels. Dr Albert will be using a number of techniques to study the function of an ion channel known as NompC, found in Drosophila melanogaster (the fruit fly). His aim is to discover whether NompC forms transducer-channels in Drosophila. This is important because recent research has found that mechano-transduction in the ear of Drosophila operates on very similar principles to those seen in vertebrate hair cells.
“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. Identifying the transducer and studying its function in a working system will significantly advance understanding of how the auditory system works.
