Hearing Aid?

Sensorineural hearing loss (SNHL) – caused by dysfunction of the cochlea or its nerve connections – is very common in the elderly population, but it’s also possible to be born with SNHL or develop it at a young age. This early-onset form is linked to various genes – most recently, the gene for carboxypeptidase D (CPD). CPD regulates production of the signalling molecule nitric oxide (NO) via arginine (an amino acid) processing, and studies show that cells from SNHL patients with CPD mutations have unusually low levels of NO. Studies of a fruit fly model of CPD deficiency revealed the animals have cellular abnormalities in their equivalent of the cochlea – Johnston's organ (pictured) – and display behaviours consistent with auditory impairment. Importantly, this could be partially rescued when the flies were given arginine to support NO production, raising hope that treatments targeting the CPD/arginine/NO pathway might help restore hearing in SNHL patients too.

Written by Ruth Williams

Ruth Williams

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Ruth is a freelance science journalist based in the US. She's a regular correspondent for The Scientist, and her work has appeared in The Lancet, Nature, Scientific American Mind, BBC Focus and elsewhere. Twitter @rooph

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• Image by Natalie Ortiz-Vega, Chong Li, & Rong Grace Zhai. Relating to article by Memoona Ramzan and colleagues
• John P. Hussman Institute for Human Genomics and Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL, USA
• Image originally published with 'please credit': Equates to Creative Commons Attribution 4.0 International (CC BY 4.0)
• Research published in The Journal of Clinical Investigation, September 2025