A better understanding of hearing loss
Repulsion for better connectionTo explore their theory of chemorepulsion, Jean Defourny and Brigitte Malgrange decided to examine the expression pattern for two types of proteins: Ephrins and their receptors (Ephs). "There are about twenty Ephrins and half as many Eph receptors. We focused on proteins that had a complementary expression pattern in the inner ear. That is, the ones which express Ephrin in the outer hair cells and have receptors in the type I spiral ganglion neurons," states Brigitte Malgrange. That's how they realized that Ephrin-A5 is exclusively expressed in outer hair cells while its cognate EphA4 receptor is located specifically in the type I neurons. "When the Ephrin-A5 binds to the EphA4 receptor, this creates a repulsion of the type I neuron projections," says the researcher. These results, published in the journal Nature Communications (1), were the first to demonstrate the chemorepulsion of neurites by Ephrins in the inner ear. A new avenue for hearing restorationWhile this discovery is still in the fundamental research stage, in the long term it could lead to therapies to restore hearing in people affected by hearing loss. "If we understand how auditory function develops, we can try to restore connections between the hair cells and the spiral ganglion neurons. Thanks to our research, we now know how it's possible to prevent type I neurons from connecting to outer hair cells," explains the director of the GIGA-neurosciences research unit. (1) Defourny J, Poirrier AL, Lallemend F, Mateo Sánchez S, Neef J, Vanderhaeghen P, Soriano E, Peuckert C, Kullander K, Fritzsch B, Nguyen L, Moonen G, Moser T, Malgrange "B. Ephrin-A5/EphA4 signalling controls specific afferent targeting to cochlear hair cells." Nat Commun 2013 Feb 5.:1438. |
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