Figure 6: Over-expressing whirlin fails to restore stereocilia staircase pattern in Cib2^KO/KO mice.

A. Representative scanning electron micrographs of OHC bundles from the apical, mid and basal cochlear turns of 2-week old mice. Cib2^+/+ and heterozygous Cib2^KO/+ mice have bundles that are very similar in appearance. OHC bundles of Cib2^KO/KO mice are poorly developed, displaying a crescent shape rather than the usual W-shape formation, and the staircase is poorly defined. Similar to IHC bundles, OHC bundles of Cib2^KO/KO;whirlin^wi/+ mice show no obvious difference from those of Cib2^KO/KO mice indicating that whirlin haploinsufficiency does not overtly potentiate the Cib2 null phenotype. However, OHC bundles of Cib2^KO/KO;whirlin^wi/wi and Cib2^KO/+;whirlin^wi/wi mice are very poorly developed. n ≥3 for each genotype.

B. Representative scanning electron micrographs of IHC and OHC bundles from the apical, mid and basal cochlear turns of 2-week old Cib2^KO/KO;whirlin^BAC279 mice. The shape and appearance of IHC and OHC bundles appear grossly similar to those of Cib2^KO/KO mice, indicating that over-expression of whirlin does not affect the Cib2 null phenotype. n ≥3 for each genotype.