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Scientists at The Scripps Research Institute (TSRI) in La Jolla, California, have identified the protein responsible for converting sound waves in to electrical impulses, which makes hearing possible. Sound waves travel through the ear and are converted in to electrical impulses, transmitted to the nervous system, which the brain recognizes as sounds, words and music. A protein called TMHS forms the mechanotransductions channels that make it possible.

Scientists discovered that when the protein is missing in laboratory mice, who have inner ears similar to human beings, the mice cannot perceive sound. Findings of the study, led by the Dorris Neuroscience Center at TSRI, were published in the December issue of the journal Cell.

How Mammals (Including Humans) Hear

Hearing occurs when mechanical vibration waves hit the outer ear, moving down the ear canal, and eventually striking the eardrum. The eardrum then moves a set of bones, which communicate the vibrations to the cochlea, a fluid-filled spiral in the inner area. The moving bones cause the fluid inside the cochlea to move. Within the cochlea, hair-like cells with extensions called stereocilia then move, causing protein channels within the ear to open. Mechanotransduction, one of the final steps in the process of hearing, occurs when these receptor cells in the ear convert the vibrations in to electrical signals, which are transmitted along nerve fibers to areas of the brain that interpret sound.

When the protein is missing, the hair cells do not convert the vibrations in to electrical signals, and hearing cannot occur. Many genetic forms of deafness, and 50% of all hearing loss is caused by genetics, are attributed to a lack of the hair cells to work the way they should. This is called auditory neuropathy. and it has just been discovered that, in some cases, this may be caused by a lack of the TMHS protein.

Promising Gene Therapy Research for Deafness Cures

Discovering this key protein leads scientists down the road to promising new gene therapy. Research scientists placed functional TMHS in to the sensory cells of deaf, newborn mice, and the mice were able to hear.

In an article published on Science Daily detailing the research, Ulrich Mueller, PhD, a professor in the Department of Cell Biology and director of the Dorris Neuroscience Center at TSRI, said,

In some forms of human deafness, there may be a way to stick these genes back in and fix the cells after birth.

Additionally, the research leads scientists closer to understanding how organisms convert mechanical signals to electrical signals, the language of the brain.

Stem Cells Another Possible Cure for Some Forms of Deafness

This research follows promising stem cell research in the United Kingdom, which showed stem cells as a potential way to treat deafness caused by auditory neuropathy. Stem cells implanted in gerbils grow to replace the early stage auditory neurons and sensory hair cells in the cochlea which convert the mechanical signals to electrical signals.

The gene therapy introduced by TSRI researchers could derive and introduce the protein through a therapeutic protein drug, which would make it a much less controversial treatment than treatments involving embryonic stem cells.

Previously, the only successful treatment for auditory neuropathy has been cochlear implants. While the laboratory treatments in mice and gerbils were successful in restoring hearing, this research may not lead to effective human treatments for deafness for several years. Nevertheless, the developments are worth watching.