Figure 7

Figure 7 Kif1aa is important to maintain synaptic vesicles at ribbon synapses

A,B, example live images of neuromasts at 5 dpf in a kif1aa mutant (B) or sibling control (A) at 5 dpf. Synaptic vesicles are labelled with LysoTracker Green (green), and ribbons are labelled with Rib a‐TagRFP (magenta). The yellow dashed lines in A and B were used to create the insets shown to the side. The top inset image shows the base of this single hair cell labelled with Lysotracker (green) and Rib a‐TagRFP (magenta), while the bottom inset shows just LysoTracker (grey). Insets are only a partial projection (single cell) of the larger image. The yellow dashed circles indicated ROIs used to quantify LysoTracker intensity at ribbons. C, the average LysoTracker intensity at ribbons is significantly lower in kif1aa mutants compared with sibling controls (control: 2580 ± 450; kif1aa: 1810 ± 650, n = 10 control and kif1aa neuromasts, unpaired t test, P = 0.0003). D, schematic of an individual hair cell with a ribbon (black dashed box) like ones examined for TEM. E–H, representative TEM images of ribbon synapses from kif1aa mutants (G,H) or wild‐type sibling controls (E,F) at 5 dpf. In E ‘tethered vesicles’ are in blue, ‘readily releasable vesicles’ in orange, while ‘the reserve pool’ within 200 nm of the ribbon is encompassed by the yellow dashed line. I‐K, all synaptic‐vesicle pools are reduced in kif1aa mutants compared with sibling controls (I, readily releasable, control: 7 ± 1.8; kif1aa: 3.7 ± 2.0, unpaired t test, P < 0.0001; J, tethered, control: 21.1 ± 3.5; kif1aa: 13.4 ± 5.3, unpaired t test, P = 0.0001; K, reserve pool, control: 36.3 ± 23.0; kif1aa: 9.7 ± 5.9, unpaired t test, P = 0.0005). n = 14 control and kif1aa ribbons in I–J, and n = 12 control and 13 kif1aa ribbons in K. Scale bars in A = 5 µm, inset is 0.1 µm, F = 250 nm.