Altered cochlear fibrocytes in a mouse model of DFN3 nonsyndromic deafness

DFN3, an X chromosome-linked nonsyndromic mixed deafness, is caused by muta tions in the BRN-4 gene, which encodes a POU transcription factor. Brn-4-de ficient mice were created and found to exhibit profound deafness, No gross morphological changes were observed in the conductive ossicles or cochlea, although there was a dramatic reduction in endocochlear potential. Electron microscopy revealed severe ultrastructural alterations in cochlear spiral Ligament fibrocytes. The findings suggest that these fibrocytes, which are mesenchymal in origin and for which a role in potassium ion homeostasis has been postulated, may play a critical role in auditory function.