Figure 10.

Endocytosis in VHC-I and IHCs. A, A single high-intensity UV flash rising [Ca²⁺]_i near 80 μm (data not shown) produced a large Δ_Cm response in control VHC-I (dark blue line, mean of 7 cells) and a reduced Δ_Cm response in Otof ^−/− VHC-I (red line, mean of 7 cells). B, Same as in A but in control IHCs (light blue line, mean of 13 cells) and in Otof ^−/− IHCs (red line, mean of 7 cells). A′, B′, Example of endocytosis in VHC-I and IHCs, respectively. Endocytosis was essentially analyzed as described by Neef et al. (2014). Briefly, the amplitude of fast endocytosis was measured as the difference between the maximum Δ_Cm (“1”) and the point where the rate of endocytosis is reduced to 5% of the instantaneous rate (“2”). To calculate the endocytotic instantaneous rate, we used a linear fit function at the point giving the faster rate between point “1” and point “2”. C, Histogram plot of the endocytotic instantaneous rate obtained in each group. We found a reduced instantaneous rate in Otof^−/− VHC-I compared with VHC-I controls (p = 0.011) but also in Otof^−/− IHCs compared with IHCs controls (p = 0.006). D, Rate constants were obtained after normalizing the instantaneous rate to the amplitude of endocytosis. No statistical differences were found between control and Otof^−/− mice (VHC-I, p = 0.051; IHCs, p = 0.55). E, Percentage of membrane retrieval at the point corresponding to 5% of the maximal instantaneous rate (point “2”) normalized by the amplitude of exocytosis ((“1” − “2”)/“1” × 100). The absence of otoferlin did not interfere with the endocytotic capability of VHC-I and IHCs. C–E, Results are expressed as mean ± SEM. *p < 0.05. # p < 0.001. n.s., No statistical difference.