Figure 3.

Disruption of the outer spiral bundle structure (OSB; type II spiral ganglion neurites form the outer spiral bundles) in Prph knockout (KO) vs. wildtype (WT) mouse cochleae from apex to mid region. Arrows in the low-power images indicate the corresponding regions of these whole-mount preparations which are shown at high resolution. The outer spiral fibers run parallel to the tunnel of Corti within the OSB (arrows), whereas the MOC fibers project across the tunnel from the inner spiral plexus (ISP) region to the outer hair cell (OHC) region, where they branch to innervate multiple OHCs. Note the comparatively higher number of outer spiral fibers in the apical region in the WT (A) (filled arrow), compared with the mid-cochlear region in the same tissue (C), (filled arrowhead). The corresponding regions in the wholemount KO cochlea (B,D); (open arrow and open arrowhead) show minimal labeling in the OSB. Note the equivalency between KO and WT, of the medial olivocochlear (MOC) efferent axon projections to the OHCs. Maximum intensity projection β-III tubulin immunofluorescence confocal images of the organ of Corti (imaged from the basilar membrane surface to optimally resolve the OSB). IHC, inner hair cell region. See also Supplementary materials 4, 5 for 3D rendering.