Australian researchers have discovered the reason why a genetic mutation is causing hearing loss for some in their early-twenties, rather than in their sixties.
Specialised ear cells destroyed
In 2010, a connection between a novel genetic mutation and hearing loss was identified. Now research shows how the mutation is causing a malfunction of the inhibitor SERPINB6, which protects the inner ear.
Individuals who lacked the healthy gene because of the genetic mutation were reported to lose their hearing from 20 years of age.
“This is unusual because most people show gradual signs of age-related hearing loss from 60 years of age onwards but mutations in SERPINB6 accelerate this process,” said Dr. Justin Tan from University of Melbourne.
Working with mice as animal models to mimic the progression of hearing loss in humans caused by SERPINB6-acceleration, the researchers found that specialised hearing cells in the inner ear were affected.
When examining the inner ears of the subjects under a microscope, the Australian researchers discovered how the sensory hair cells, and the neighbouring fibrocytes that support them, had died. Both types of cell are fundamental to the transformation of sounds into signals in our hearing nerve.
Even though mutations affecting the hair cells have been known to lead to hearing loss for decades, the effect on fibrocytes is new and significant.
“We are finally beginning to understand the role of these proteins in protecting our hearing,” said Professor Philip Bird from Monash University in Australia, who led the research.
The research was conducted by scientists from the Department of Biochemistry and Molecular Biology at Monash University and the Department of Otolaryngology at the University of Melbourne.
The study was published in the American Journal of Pathology.