(A) After a 48-hour incubation in culture medium with 1 mM gentamicin, wild-type utricular hair bundles were almost completely eliminated, while Tmc1Δ/ΔTmc2Δ/Δ utricular hair cells retained an intact hair bundle. Scale bar: 10 μm. (B) The mean density of intact hair bundles (±SD) within the central area of more than 6 utricular maculae of each genotype is shown for each genotype. Tmc1Δ/+Tmc2Δ/Δ and Tmc1Δ/ΔTmc2Δ/Δ utricular maculae showed no significant difference between cultures grown with gentamicin in comparison with control cultures grown without gentamicin. Tmc1+/+Tmc2Δ/Δ utricular hair cells showed intermediate sensitivity to gentamicin. One-way ANOVA results for differences from normal control values are indicated: *P < 0.05; ***P < 0.001; NS, P > 0.05. (C) After a 6-hour incubation in culture medium with 1 mM gentamicin, robust immunoreactivity for gentamicin was detected in wild-type utricular hair cells, whereas no immunoreactivity for gentamicin was detected in Tmc1Δ/ΔTmc2Δ/Δ hair cells. Red, anti–myosin VI antibodies; green, anti-gentamicin antibodies. Scale bar: 10 μm. (D) After a 6-hour incubation in 1 mM gentamicin, robust immunoreactivity for gentamicin was detected in wild-type IHCs and OHCs, whereas no immunoreactivity for gentamicin was detected in Tmc1Δ/ΔTmc2Δ/Δ hair cells. Red, anti–myosin VI antibodies; green, anti-gentamicin antibodies. Filled arrowheads, IHCs; open arrowheads, OHCs. Scale bar: 10 μm. See also Supplemental Figures 7 and .