Wnt signaling in the cochlea

The process by which cells orient themselves correctly within the plane of an epithelial tissue is known as planar polarity. The molecular mechanism of planar polarity is understood best in fruit flies, but whether the same genes are at work in vertebrates has been unclear. In the June 1 Development, Alain Dabdoub and colleagues at the National Institute of Deafness and Other Communication Disorders, Bethsheda, Maryland, US, provide the first evidence for the conservation of planar polarity mechanisms in mice (Development 130:2375-2384, June 1, 2003).

In mammals, planar polarity is exhibited by the fine protrusions, known as stereociliary bundles, of the hair cells of the cochlea in the inner ear. The mechanosensory stereociliary bundles within each cell are organized in a chevron; all chevrons are polarized in the same direction — toward the outer border of the cochlear duct. Misorientation of even a few of the bundles...