Scientists at the Institut Pasteur, Inserm, the Collège de France and Pierre & Marie Curie University, working closely with scientists at the University of Auvergne, have recently discovered the function of pejvakin, a molecule that plays a vital role in the hearing system. The absence of this molecule appears to be responsible for noise-induced hearing loss, one of the most common causes of deafness. The scientists' discovery, which was published on November 5 in the journal Cell, offers new prospects for the treatment of this condition.
In 2006, the team led by Christine Petit in the Institut Pasteur's Genetics & Physiology of Hearing Unit, especially Sedigheh Delmaghani, working in cooperation with Paul Avan's team at the University of Auvergne's Laboratory of Sensory Biophysics, identified a new gene that was responsible for early-onset sensorineural hearing loss. This gene codes for a protein which was given the name "pejvakin" (which means "echo" in Persan).
Audiometric tests performed on individuals with mutations in this gene subsequently revealed an unusually high level of diversity in hearing impairments, in terms of both severity and characteristics. This latest study, carried out by scientists from the Institut Pasteur, Inserm, the Collège de France, Pierre & Marie Curie University and the University of Auvergne, aimed to clarify the reasons for this heterogeneity.
The scientists, particularly Sedigheh Delmaghani, studied young mice whose pejvakin gene had been inactivated. Their observations revealed an astonishing variation in hearing impairments from one mouse to the next, ranging from mild to profound hearing loss. Young mice are highly vocal for the first three weeks after they are born, particularly when feeding.
The more mice there are in the cage, the noisier their acoustic environment. The scientists observed that as the number of mice in the cage increased, so did their hearing threshold - the minimum sound level at which they are able to hear sounds. Using direct, controlled acoustic stimulation, the scientists were able to prove that the auditory system of mice lacking in pejvakin is affected by their acoustic environment.
The scientists then set about investigating the physiological causes of this phenomenon. They observed that in mice without pejvakin, the auditory sensory cells are damaged as soon as they are exposed to even seemingly harmless sounds - the equivalent of a minute spent in a nightclub for humans. These cells need two weeks of silence to become functional again.
With prolonged or repeated exposure, the cells eventually die. The scientists also identified the noise-sensitive element in the cell as being the peroxisome, a small organelle involved in detoxification. "To put it simply, we discovered that a genetic disorder could be responsible for noise-induced hearing loss triggered by even very low noise levels," explained Christine Petit.
The auditory sensory cells in people with impaired pejvakin were observed to be extremely vulnerable to noise. When a standard hearing test was performed on these hearing-impaired individuals, the responses of their auditory sensory cells and neurons, although normal to begin with, gradually worsened as the test went on as a result of the sounds used.
Noise-induced hearing loss is becoming increasingly prevalent. Urban crowding means that large cities are getting noisier, particularly in developing countries. WHO predicts that by 2030, one billion people will be at risk of noise-induced hearing loss.
"Some of us have less effective natural defenses against the impact of overexposure to sound than others," explained Profs. Avan and Petit. "Five million people in France end up suffering from hearing loss, which has a negative impact on their social life. Hearing aids are one solution, but they work by exposing the wearer to amplified sounds. However, we don't yet know what percentage of the population is either lacking in pejvakin or has a less effective form of the protein. Our findings indicate that in these people, hearing aids are most probably not only ineffective but also harmful."
The scientists will now look into possible techniques to restore the function of pejvakin, particularly using gene therapy, which has already proved successful in conserving hearing in mice lacking in pejvakin, even when they are overexposed to noise.
This study received funding from the Louis-Jeantet Foundation, the Bettencourt Schueller Foundation, Humanis, AG2R La Mondiale, the BNP Paribas Foundation and Agir pour l'Audition Foundation.
Myriam Rebeyrotte | EurekAlert!
New malaria analysis method reveals disease severity in minutes
14.08.2017 | University of British Columbia
New type of blood cells work as indicators of autoimmunity
14.08.2017 | Instituto de Medicina Molecular
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
17.08.2017 | Physics and Astronomy
17.08.2017 | Earth Sciences
17.08.2017 | Physics and Astronomy