Drugs that can prevent hearing loss are already available in the marketplace

In a study led by the University of California, San Francisco (UCSF), scientists have discovered a gene that plays a pivotal role in hearing loss, opening new avenues for treatment. This gene, known as TMTC4, is linked to cell death in the inner ear, a key factor in deafness. 

Study significance

The research, published in the Journal of Clinical Investigation Insight, holds promise for developing strategies to prevent hearing loss, which until now has been largely irreversible.

Hearing loss can result from various factors including loud noise exposure, aging, and certain medications, with few options beyond hearing aids or cochlear implants for treatment. The UCSF team’s research, however, marks a significant step in understanding the inner ear’s mechanisms during hearing loss.

Common cause of hearing loss

The study connects findings from animal research on hearing loss to a rare type of inherited deafness in humans. It was observed that mutations in the TMTC4 gene trigger a chain reaction known as the unfolded protein response (UPR), leading to the death of hair cells in the inner ear. 

Notably, this UPR activation is also seen in hearing loss due to loud noises or certain drugs, suggesting it could be a common underlying cause of various forms of deafness.

Target for preventing deafness 

There are several drugs that block the UPR, and stop hearing loss in laboratory animals, the researchers note, advocating for testing these drugs in people at risk of hearing loss.

“We now have solid evidence that TMTC4 is a human deafness gene and that the UPR is a genuine target for preventing deafness,” said Dylan Chan, MD, PhD, co-senior author of the paper and director of the Children’s Communication Center (CCC) at UCSF’s Department of Otolaryngology.

Key insights into hearing loss prevention

The research initially began with an observation by Elliott Sherr, MD, PhD, co-senior author and director of the UCSF Brain Development Research Program. Sherr noticed that many young patients with brain malformations had mutations in TMTC4. 

This led to the discovery that mice with TMTC4 mutations showed signs of accelerated age-related hearing loss, linking these mutations to self-destructive processes in hair cells.

This discovery was further validated through international collaboration. In 2020, scientists from South Korea, led by Bong Jik Kim, MD, PhD, found genetic mutations in TMTC4 in two siblings experiencing hearing loss in their mid-20s. These findings were consistent with those observed in the animal studies by Chan and Sherr.

Study implications 

The potential implications of this research are far-reaching. Beyond addressing hearing loss, the study suggests that targeting the UPR could also be beneficial in treating other diseases where nerve cells are overwhelmed and die, such as Alzheimer’s or Lou Gehrig’s disease.

“If there’s any way that we can get in the way of the hair cells dying, that’s how we’re going to be able to prevent loss,” Chan concluded, highlighting the transformative impact this discovery could have on treating and preventing deafness and possibly other neurodegenerative diseases.

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