Figure 2

The expression of BK subunits during development of the chick basilar papilla. Cross-sections of the chick cochlear were stained with anti-BK (Chemicon) to qualitatively correlate protein levels with gene expression levels. Panels are organized by tonotopic position (base-to-apex, left-to-right) and age (E19-to-E12, top-to-bottom). Each cross-section is positioned so that the inferior to superior radial axis lies from left-to-right. Cochlear nerve projections were immunopositive as were the base of tall hair cells lying along the superior-most portions of most sections. Antibody specificity was confirmed using Western blot on membrane fractions from chick brain (inset in panel A). The dominant band appeared near 140 kDa, matching the predicted weight of the long C-terminus BK α variant. Additional bands near this molecular weight may be other splice forms or proteolytic by-products. No other spurious bands were observed in the blot. Scale bar in (B) is applicable to all panels. TM, tectorial membrane. HC, hair cell layer. CG, cochlear ganglion projections.