Figure 3: Transients predominantly originate near the stereocilia tip but are occasionally observed in the middle and basal regions.

A) A kymograph of a transient is shown. The yellow dashed line marks the stereocilium tip. Transients predominantly originate near the stereocilium tip. Frames are 400 ms apart. B) Line intensity profiles along the length of 15 stereocilia were measured at the first frame where a transient was seen. The values were normalized to the maximum intensity of each trace. The mean and SEM are plotted here. The resulting graph shows that the origin of the transients is predominantly at the stereocilia tip. C) Within the same stereocilium, transients can originate from different locations as shown in this example. The line intensity profiles along the length of this stereocilium are plotted at the first frame a calcium transient is seen for 4 transients. The transients originate from different points along the length of the stereocilium, marked by stars. D) Transients are occasionally seen to originate from unexpected locations such as (i) in the tallest row in the organ of Corti where the MET channel is not believed to be present (right, shown in a P5 inner hair cell), (ii) at the base of stereocilia (middle, shown in a P9 vestibular hair cell), and (iii) in the middle of stereocilia (right, shown in a P4 vestibular hair cell). Scale bars are 1 μm.