Molecular Remodeling of Tip Links Underlies Mechanosensory Regeneration in Auditory Hair Cells
Figure 4
MET regenerates in two distinct steps.
(A) Maximal MET current in control IHCs (black) and in IHCs at different times after BAPTA treatment (red). All records were obtained in “optimal” position of the probe (see Figure 3) at holding potential of −90 mV. n, number of cells. (B) Number of “tip” (blue) and “top” (black) links per stereocilium in control IHCs (dashed lines) and in IHCs recovering from BAPTA (solid lines). From 5 to 12 IHCs (154–502 stereocilia) were analyzed for each data point. (C) Representative SEM image of an IHC stereocilia bundle shows tip (blue dots) and top (black dots) links. See the text for exact definitions of “tip” and “top” links. (D) Current–displacement relationships of MET current at different stages of regeneration. Data were fitted to a second-order Boltzmann function and normalized to the maximum MET current obtained from the fit [50]. (E) Overlapping MET currents evoked by a small bundle deflection (150 nm, bottom trace) that increases the open probability of MET channels (P/Pmax) by ∼30%. To compare adaptation at different time points of tip link regeneration, MET responses were normalized to peak current and averaged. Standard errors were calculated for each point of the trace, but shown only at five time points for clarity of the figure. (F) Extent of adaptation calculated at 1.6 ms (1) and 7.6 ms (2) after the beginning of bundle deflection at different stages of MET recovery. Black dashed lines show the data from control IHCs untreated with BAPTA. The same MET records contribute to (A), (D), (E), and (F). All averaged data are shown as mean ± SE. Asterisks indicate statistical significance from the control values: * p<0.05; ** p<0.01; *** p<0.001 (t test of independent variables). Age of the cells: P3+2–4 div (dissected at P3 and kept in vitro for 2–4 d).