, Top) scanning electron microscopy analysis of IHCs from Ush1g flScale bar: 1 ?m.) In Ush1g ?/? IHCs, some stereocilia of the second row (about 10%) have a prolate end shape, which suggests that some tip-links are still present. Note the reduced length of most stereocilia from the small and medium rows. (Middle) Examples of transduction current recordings in an Ush1g fl/fl IHC (Left panel in dark-red) and an Ush1g ?/? IHC from P5 mice while applying different displacement steps with a glass probe in the excitatory direction and a 150-nm step in the inhibitory direction (calibrated voltage command of the stimulator at the top). (Bottom) Mean maximum transduction currents and P o (X) curves plotted for Ush1g fl/fl and Ush1g ?/? P5 mice. The maximal amplitudes of the transduction current are 51 ± 9 pA and 471 ± 40 pA in Ush1g ?/? and Ush1g fl/fl IHCs, respectively (unpaired t test, P < 10 ?4 ). The averaged sensitivity of the transduction currents to hair bundle displacement in the mutant IHCs, inner hair cells (IHCs) and outer hair cells (OHCs) from Ush1g ?/? P5 mice ?/? and Ush1g fl/fl IHCs, respectively, pp.10-13
, Note the fragmented aspect of the hair bundles and the reduced length of most stereocilia from the small and medium rows. However, one can recognize the stereocilia of the first row and some stereocilia of the second row. (Scale bar: 1 ?m.) (Middle) Examples of transduction current recordings in a Ush1g fl/fl OHC and two Ush1g ?/? OHCs from P5 mice. (Bottom) Mean maximum transduction currents and P o (X) curves plotted for Ush1g fl/fl and Ush1g ?/? P5 mice. The maximal amplitudes of the transduction current are 91 ± 24 pA and 696 ± 50 pA in Ush1g ?/? and Ush1g fl/fl OHCs, respectively (unpaired t test, P < 10 ?3 ). The averaged sensitivity values are 1, Top) Scanning electron microscopy analysis of OHCs from Ush1g fl in Ush1g ?/? and Ush1g fl/fl OHCs, respectively, pp.10-14
, A) Examples of transduction currents in midcochlear IHCs from Ush1g fl/fl (black) and Ush1g fl Mean maximum current amplitude is 616 ± 67 pA and 664 ± 71 pA for Ush1g fl/fl and Ush1g fl/fl Myo15-cre +/? IHCs, respectively (unpaired t test, P = 0.63) The P o (X) curves can be superimposed with values of averaged sensitivity 2.03 ± 0.10 ?m ?1 and 1.85 ± 0.14 ?m ?1 for Ush1g fl/fl and Ush1g fl/fl Myo15-cre +/? , respectively (unpaired t test, P = 0.35) In addition, no change in X 0.5 could be detected in the mutant IHCs with values 248 ± 23 nm and 273 ± 34 nm in Ush1g fl/fl and Ush1g fl/fl Myo15-cre +/? , respectively (unpaired t test, P = 0.55). (B) We characterized the adaptation in Ush1g fl/fl and Ush1g fl/fl Myo15-cre +/? IHCs in terms of its extent and kinetics. The adaptive decline of the transduction current I as a function of time t was fitted by the double exponential relation I(t) In this equation, t 0 is the time at which the stimulus was applied, the fast and slow components of adaptation are characterized by their magnitudes, A F and A S , and time constants, ? F and ? S , respectively , and A SS describes the transduction current at steady state. From the fit, we deduced the fast and slow adaptation rates, 1/? F and 1/? S , and the proportions Statistical significance was tested by using either two-way analysis of variance coupled to the Bonferroni posttest (two-way ANOVA) or two-tailed unpaired t test with Welch's correction using the Prism software (GraphPad) We compared the extent of adaptation, Analysis of mechanoelectrical transduction current adaptation in inner hair cells (IHCs) from Ush1g fl respectively, as well as the extent of adaptation 1 ? A SS the fast adaptation proportion, and the fast and slow adaptation rates in Ush1g fl/fl and Ush1g fl/fl Myo15-cre +/? mice, and no change could be detected in the mutant IHCs
, A and B: ?35% the total length of the cochlea from the apex) and the middle region (C and D: ?55% the total length) in Ush1g flA) Examples of transduction currents in apical OHCs from Ush1g fl/fl (black) and Ush1g flblue) P8 mice Mean maximum current amplitude is 1,014 ± 82 pA and 866 ± 67 pA for Ush1g fl/fl and Ush1g fl/fl Myo15-cre +/? inner hair cells (IHCs), respectively (unpaired t test, P = 0.19) The P o (X) curves can be superimposed, with values of averaged sensitivity of 3.89 ± 0.38 ?m ?1 and 3.41 ± 0.18 ?m ?1 for Ush1g fl/fl and Ush1g fl/fl Myo15-cre +/? , respectively (unpaired t test, P = 0.28) In addition, no change in X 0.5 could be detected in the mutant OHCs, with values of 188 ± 23 nm and 196 ± 12 nm in Ush1g fl/fl and Ush1g fl/fl Myo15-cre +/? , respectively (unpaired t test, P = 0.9). (B) We characterized the adaptation in Ush1g fl/fl and Ush1g fl/fl Myo15-cre +/? OHCs from the cochlear apex in terms of its extent and kinetics. We compared the extent of adaptation, the fast adaptation proportion, and the fast and slow adaptation rates in Ush1g fl/fl and Ush1g fl/fl Myo15-cre +/? mice, and no change could be detected in the mutant OHCs (two-way ANOVA, respectively). (C) Examples of transduction currents in an Ush1g fl/fl OHC (black) and an Ush1g fl/fl Myo15-cre +/? OHC (pink) from the middle of the cochlea at P8. Mean maximum current amplitude is 963 ± 91 pA and 1,009 ± 60 pA for Ush1g fl/fl and Ush1g fl/fl Myo15-cre +/? OHCs, respectively (unpaired t test, P = 0.69). The P o (X) curves can be superimposed with values of sensitivity 3, Mechanoelectrical transduction current recordings in outer hair cells (OHCs) from Ush1g fl P8 in hair cells from the cochlear apical region addition, no change in X 0.5 could be detected in the mutant IHCs, with values of 179 ± 19 nm and 213 ± 29 nm in Ush1g fl/fl and Ush1g fl/fl Myo15-cre +/? IHCs, respectively (unpaired t test, P = 0.34). (D) We characterized the adaptation in Ush1g fl/fl and Ush1g fl/fl Myo15-cre +/? OHCs from the middle in terms of its extent and kinetics. We compared the extent of adaptation, the fast adaptation proportion and the fast and slow adaptation rates in Ush1g fl/fl and Ush1g fl/fl Myo15-cre +/? mice, and no change could be detected in the mutant OHCs