Fig. 5
The functional MET current is required for retaining mature IHC characteristics. a, b MET currents recorded from mature IHCs of control Myo7afl/fl (a, P15) and Myo7afl/flMyo15-cre+/- (b, P14 and P16) mice. Protocol as in Fig. 2a. c Peak-to-peak MET current-voltage curves obtained from six P15 Myo7afl/fl (2 mice), four P14 Myo7afl/flMyo15-cre+/- and six P16 Myo7afl/flMyo15-cre+/- IHCs (3 mice). d Scanning electron microscopy images showing the stereociliary bundle of apical-coil IHC from P30 control Myo7afl/fl and Myo7afl/flMyo15-cre+/- mice. s1 and s2 represent the tallest and the second tallest stereocilia, respectively. The arrows in the middle panel highlights that tip links, which are required to gate the MET current, are present in Myo7afl/flMyo15-cre+/- IHCs. Scale bars, 1 μm. e Transmission electron microscopy images (left) showing the stereocilia s1 and s2 (see panel d) of apical-coil IHCs from P37 control Myo7afl/fl and Myo7afl/flMyo15-cre+/- mice. Scale bars, 400 nm. The right panels show that the height and width of s1 and s2 stereocilia in IHCs are comparable between the two genotypes (Myo7afl/fl s1: height 4.42 ± 0.48 μm, width 0.36 ± 0.07 μm, n = 6 IHCs, s2: height 1.58 ± 0.10 μm, width 0.32 ± 0.04 μm, n = 7, s1/s2: 2.77 ± 0.36, n = 6; Myo7afl/flMyo15-cre+/- s1: 4.44 ± 0.20 μm, P < 0.8915, 0.38 ± 0.03 μm, P < 0.4441, n = 7, s2: 1.61 ± 0.18 μm, P < 0.7849, 0.33 ± 0.06 μm, P < 0.8959, n = 7, s1/s2: 2.80 ± 0.35, P < 0.9059, n = 6). f–h Potassium currents recorded from IHCs of young adult (f, P19 and P21), adult (g, P59) and aged (h, P210 and P218) control Myo7afl/fl (left panels) and Myo7afl/flMyo15-cre+/- (right panels) mice. Protocols are as in Fig. 3a. i Size of IK,f, IK,n, membrane capacitance (Cm) and resting membrane potential (Vm) as a function of postnatal age. Number of IHC investigated is shown above or below the symbols (for more details see Supplementary Table 3). Statistical tests are performed with two-way ANOVA with Bonferroni correction. Average data is shown as mean ± SEM (c, i) or mean ± SD (e)
