(A, B) At P9, SEM analysis in the 45-kHz cochlear region in cKO and control mice showed a comparable appearance of OHC hair bundles. Hair bundle orientation and cohesion appeared unperturbed by the mutation at this immature age. (C, D) High-magnification images of single bundles show no apparent differences in stereocilia length or organization. (E, F) Close-up images of 45-kHz OHC hair bundles show the presence of inter-sterociliary links (arrowheads) in both genotypes. Abbreviations: B6, C57BL/6J strain; cKO, conditional knock out; OHC, outer hair cell; SEM, scanning electron microscopy. Scale bars: (A) 5 μm A-B; (C) 1 μm C-D; (E) 200 nm E-F.