Figure 6. Tmc1^Δ and Tmc2^Δ cochlear hair cell mechanotransduction currents.

(A) Representative mechanotransduction current families recorded from OHCs harvested at P5–P7 from the apical cochlea of mice of the indicated Tmc1;Tmc2 genotypes. Hair bundles were deflected for 90-ms steps that ranged from 200 nm to 750 nm in 50-nm increments while cells were held at a physiologically relevant holding potential (–64 mV). Some traces have been removed for clarity. The envelope of the stimulus protocol is shown at the bottom right. Tmc1^Δ/ΔTmc2^Δ/Δ OHCs lack mechanotransduction currents entirely. Scale bars apply to all current families. (B) Summary bar graph of mean maximal mechanotransduction current amplitudes (±SEM) from 100 apical OHCs. For each bar, the upper number indicates the number of mice examined, and the lower number indicates the total number of hair cells examined. Tmc1^Δ/ΔTmc2^+/+ and Tmc1^Δ/ΔTmc2^Δ/⁺ hair cells had intermediate current amplitudes. *P < 0.001, 1-way ANOVA, relative to wild-type values. (C) Representative transduction currents recorded from OHCs excised at P2–P4 from the basal end of the cochlea from mice of the indicated genotypes. The stimulus protocol and scale bars in A apply. (D) Summary bar graph of maximal mechanotransduction current amplitudes (±SEM) from 45 basal OHCs. Upper numbers indicate the numbers of mice examined, and lower numbers indicate the total numbers of cells examined. *P < 0.001, 1-way ANOVA, relative to wild-type values. See also Supplemental Figure 5.