60 Million Roundworms Grown to Solve Puzzle on Human Hearing

Scientists are raising 60 million roundworms to help them figure out a long-standing mystery about human hearing.

Finally, researchers have figured out the structure of the mysterious protein complex that makes human hearing possible in the inner ear.

Researchers had to raise 60 million Caenorhabditis elegans roundworms, which use a highly similar protein complex to what humans do, to solve this long-standing mystery.

The team could only gather enough of this protein to study by turning to a different source because humans only possess a minuscule portion of this protein from within their inner ears.

Sarah Clark, a biochemist from Portland's Oregon Health and Science University (OHSU), said they spent many years perfecting the techniques for protein isolation and worm growth, and they experienced many "rock-bottom" moments where they thought about giving up. Clark is the study's co-first author.

Proteins in Human Hearing

The exact composition of the protein 1 (TMC1) complex, which somehow resembles a transmembrane channel, has remained a mystery even though researchers have widely recognized for some time that it plays a crucial role in hearing.

Eric Gouaux, a senior biochemist from OHSU, said that this is the final sensory system whose underlying molecular architecture is still unknown. Gouaux is one of the co-authors of the study.

There is no evidence, courtesy of this recent study, which was published in Nature, that this protein complex functions as a tension-sensitive ion channel that opens and shuts in reaction to the movement of hairs within the inner ear.

The protein complex brings to mind an accordion, with subunits ideally placed like handles on either side, the researchers found using electron microscopy.

The three tiniest bones in the human body, the ossicles, move when sound waves moving through the ear reach the eardrum (tympanic membrane). The cochlear, which resembles a snail, is struck by the ossicles. The cochlear then brushes membranes with stereocilia, tiny finger-like hairs.

As the hairs move, the TMC1 complex-created ion channels embedded in these stereocilia open and close, sending electrical signals following the auditory nerve to the brain where they are translated into sound.

Read also: Human Ear Evolution Study Suggests Middle Structure Developed from Prehistoric Fish Gill 

Most Awaited Results

Peter Barr-Gillespie, an otolaryngologist from OSHU, said that since these findings have finally arrived after decades of anticipation, the entire field of auditory neuroscience is overjoyed. The national expert in hearing research, Barr-Gillespie, was not associated with the study.

The discovery might one day support the creation of hearing impairment treatments by researchers.

Over 460 million people across the globe suffer from hearing loss and deafness. Researchers can continue to develop novel strategies to assist, treat, or avert hearing loss in our society by comprehending the nature of the hearing, Science Alert reports.

Types of Hearing Loss

According to CDC data, there are four different kinds of hearing loss. The first type of hearing loss is called conductive hearing loss and is brought on by a blockage in either the middle or outer ear. Medications or surgery are frequently used to treat this form of hearing loss.

The second type is sensorineural hearing loss, which takes place when the inner ear or hearing nerve functions incorrectly.

The third type of hearing loss, mixed hearing loss, includes both sensorineural and conductive hearing loss.

And fourth, auditory neuropathy spectrum disorder is a hearing loss that happens when sound normally enters the ear but is not organized in a way the brain can understand due to damage to either the inner ear or the hearing nerve.

Related article: Deafness: What Factors Influence the Effectiveness of Hearing Aids?