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Hearing impairment

Protein affects perception of frequencies

Munich, 06/25/2012

A newly identified protein has been shown to be necessary for hearing at both ends of the normally audible frequency range. The discovery enhances our understanding of hearing and may lead to new therapeutic strategies.

All mammals have highly sensitive auditory systems, which are the result of a complex evolutionary history. In particular, mammals can perceive a wider range of frequencies, and show better discrimination between similar frequencies, than any other class of vertebrates. This is made possible in part by the so-called tectorial membrane in the inner ear, which plays a central role in converting mechanical vibrations into nerve impulses and also serves as a sound amplifier.

Professor Wolfgang Zimmermann’s group at the Medical Center of the University of Munich, together with colleagues at several other institutions, has identified a protein that affects auditory responsiveness to certain frequencies. Called CEACAM16, it is a relatively recent evolutionary innovation, as it is restricted to mammals. Inactivation of the Ceacam16 gene in mice markedly reduced the ability to perceive both low- and high-frequency sounds - and the defect got worse as the mice got older.

A protein for the highs and the lows

Moreover, these symptoms mimic those seen in members of an American kindred who suffer from a congenital hearing impairment. “On the basis of our findings, we were able to confirm that the condition in this family is due to a mutation in CEACAM16,” says Zimmermann. The scientists believe that the protein may help to confer the optimal degree of elasticity on the tectorial membrane. Thus, when CEACAM16 was present, the membrane was found to adopt a less extended form than in its absence.

“CEACAM16 probably influences the physical properties of the membrane,” Zimmermann explains. The researchers hope that the findings will suggest new ways to help patients. It might even be possible to deliver intact CEACAM16 into the inner ear. (The Journal of Biological Chemistry, 22. Juni 2012)    göd/PH


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