Hair cells of a congenitally hearing impaired canary have abnormal distribution of filamentous proteins

Abstract

Previous investigations into the anatomy of the inner ear of Belgian Waterslager canaries (BWC) have demonstrated myriad malformations associated with dysgenesis of the pars inferior of the otocyst. These malformations are associated with a congenital hearing impairment primarily affecting mid to high frequencies. Specific hair cell abnormalities include irregular cell boundaries, deformed cuticular plate, and multiple and deformed stereocilia tufts. This constellation of structural deformities lead us to hypothesize that the content of non-muscle filamentous protein in BWC hair cells need be abnormal. As a first step in exploring this hypothesis, we have used immunocytochemical techniques to assess the presence and distribution of the major components of the actin microfilament system, i.e. actin, tropomyosin and α -actinin, at the apical end of hair cells from the BWC basilar papilla. Our results show qualitative differences between control and BWC hair cells. First, label of the BWC cuticular plate was scattered and ill-matched with that of control birds for each of the three proteins examined. Second, labeling of BWC cilia revealed abnormal distribution of the assessed proteins. Specifically, anti-actin and anti- α -actinin antibodies were clustered over the cilia, while immunostaining against tropomyosin was not seen. These findings support a link between the proteins associated with cochlear hair cell structural integrity and the dysmorphologies associated with the congenital hearing impairment identified in the BWC model.