In what’s described as a breakthrough decades in the making, scientists at Oregon State Health & Science University (OHSU) have revealed the inner ear architecture that converts vibrations into sound, in near-atomic detail. The discovery for the first time reveals the molecular machinery behind this fundamental sensory function, and opens up exciting new avenues of research into hearing loss.
The ability of the ear to turn vibrations into the sensation of sound is facilitated by an inner structure called the mechanosensory transduction complex. Despite its critical role in human hearing, the composition of this structure and mechanisms that underly its function have remained poorly understood.
“This is the last sensory system in which that fundamental molecular machinery has remained unknown,” said senior author of the new study Eric Gouaux. “The molecular machinery that carries out this absolutely amazing process has been unresolved for decades.”
The team’s work involved the roundworm Caenorhabditis elegans, a popular model for scientists as the creature shares a similar genome and many cellular pathways with humans. The scientists spent five years studying more than 60 million worms through cryo-electron microscopy, an emerging technique used to create 3D reconstructions of proteins.
This enabled the scientists to piece together the protein complex that turns vibrations into the electrical impulses our brain recognizes as sound. The highly detailed portrait of this intricate biological architecture has been a long time coming, according to fellow OHSU hearing scientist Peter Barr-Gillespie, who wasn’t directly involved in the research.
“The auditory neuroscience field has been waiting for these results for decades, and now that they are right here – we are ecstatic,” he said. “The results from this paper immediately suggest new avenues of research, and so will invigorate the field for years to come.”
Because hearing loss can came about through genetic mutations that change the proteins making up the mechanosensory transduction complex, an ability to now visualize the protein complex may present new ways to counter the mutations.
“It immediately suggests mechanisms by which one might be able to compensate for those deficits,” said senior author Eric Gouaux. “If a mutation gives rise to a defect in the transduction channel that causes hearing loss, it’s possible to design a molecule that fits into that space and rescues the defect. Or it may mean we can strengthen interactions that have been weakened.”
The research was published in the journal Nature.