Fig. 4. Wnt7a does not bias the direction of stereociliary bundle orientation. (A) Frequency histograms for stereociliary bundle orientations at different positions along the basal-to-apical axis in control cochleae. Orientations were determined for bundles on outer hair cells and the resulting values were used to generate a frequency histogram with a class interval of 15°. In more immature regions of the cochlea (45% and 37.5% positions) there is a broad distribution of bundle orientations. By contrast, in more mature regions of the cochlea (25%, 12.5% and 5% positions), the distribution of bundle orientations becomes tightly clustered. (B) Frequency histograms, generated as in A, for stereociliary bundle orientations in cochleae exposed to Wnt7a. The distribution of bundle orientations at the 45% position appears similar to control. However, bundle orientations remain fairly broad at more basal (mature) positions, suggesting that Wnt7a inhibits bundle reorientation rather than affecting the overall polarity of the epithelium. The data in A and B represent orientations for stereociliary bundles from cochlear explant cultures established on E13 after 6 days in vitro in the presence of either control or Wnt7a-conditiond medium.

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