Fruit flies have ears like humans
The latest research, conducted by Dr Jörg T Albert, a Deafness Research UK research fellow at the UCL Ear Institute, together with scientists at the University of Cologne, shows that fruit flies have ears which mechanically amplify sound signals in a remarkably similar way to the sensory cells found in the inner ear of vertebrates including humans. The finding means that the wealth of genetic techniques already available to study the fruit fly can now be used to target how the ear works.
Dr Albert says, “The biophysical parallels between the ways both fruit flies and humans convert sound into nerve signals are truly amazing. We may be allowed to hope that these mechanistic similarities extend further down to the genes and molecules that bring about hearing. But even if it finally should turn out that hearing in fruit flies relies on different molecules than does hearing in humans, the little fruit fly can help us find answers to some key questions of hearing research and – what is sometimes even more important – will surely help us ask the right questions.”
Vivienne Michael, Chief Executive of Deafness Research UK says “This is an important advance that paves the way toward a clear understanding of the genetics of deafness. The charity will continue to support cutting-edge research through its Fellowship programme at the UCL Ear Institute and at other top research centres in the UK to achieve our goal of securing radical improvements in the prevention, diagnosis and treatment of all forms of hearing impairment”.
There are nine million deaf and hard of hearing people in the UK and in most cases deafness results from loss of sensory cells in the inner ear known as “hair” cells. The cells can be damaged and lost through ageing, noise, genetic defects and certain drugs and, because the cells don’t regenerate, the result is progressive - and irreversible - hearing loss. Damage to these cells can also lead to tinnitus which affects around 5 million people in the UK.
Björn Nadrowski, Jörg T Albert and Martin C Göpfert report a mathematical model of the process, known as transduction, used by Drosophila melanogaster (the fruit fly) to transform mechanical energy from sound waves into electrical signals. In vertebrates this transduction is performed by hair cells which send the electrical signals on to the brain where they are understood as sounds. However, there are important structural differences between the inner ear of vertebrates and invertebrates like the fruit fly. These differences have lead researchers to believe that transduction must work on different principles.
The research team compared real data – from measurements of the amount of cochlear amplification found in the fruit fly inner ear – to the output of their model and found that around 20 transducers per sensory cell are enough to describe the real data accurately. This is the same as the number of “hairs” on a hair cell. Their results both describe the hearing organ comprehensively and open up the field of deafness research to Drosophila genetics. By manipulating the genes which control the transducers, scientists can identify which molecules are involved in allowing hair cells to send signals to higher brain centres.