Nrxn3 is required for proper hair-cell synapse function in the lateral line. (A) Side view schematic of a neuromast expressing memGCaMP6s in hair cells. The dashed box indicates the region used to measure presynaptic GCaMP6s responses. (B,C) ΔF heatmaps showing presynaptic GCaMP6s increases in hair cells before (B) and during (C) a 500 ms fluid-jet stimulation in a wild-type neuromast. ROIs (circled) indicate synaptically active hair cells. The black area in the center of each cell is the nucleus. (D) ΔF/F0 GCaMP6s traces showing average presynaptic responses during stimulation for wild-type controls (black) and nrxn3a; nrxn3b mutants (blue). (E) Maximum ΔF/F0 presynaptic calcium responses are significantly reduced in nrxn3a; nrxn3b mutants. n=15 wild-type and 14 nrxn3a; nrxn3b mutant neuromasts at 5-6 dpf. (F) Side view schematic of a neuromast expressing GCaMP6s in afferent terminals beneath hair cells. The dashed box indicates the region used to measure postsynaptic GCaMP6s responses. (G,H) ΔF heatmaps showing postsynaptic GCaMP6s increases in afferent terminals before (G) and during (H) a 500 ms fluid-jet stimulation in a wild-type neuromast. ROIs (circled) indicate synaptically active terminals. (I) ΔF/F0 GCaMP6s traces showing average postsynaptic responses during stimulation for wild-type controls (black) and nrxn3a; nrxn3b mutants (blue). (J) Maximum ΔF/F0 postsynaptic calcium responses to stimulation for wild-type controls and nrxn3a; nrxn3b mutants. n=13 wild-type and 22 nrxn3a; nrxn3b mutant neuromasts at 4-5 dpf. Traces in D and I are displayed as mean, dashed lines are s.e.m.; gray bar denotes the stimulus. Each dot in E and J represents the average response from a single neuromast. A Mann–Whitney U-test was used in E and an unpaired two-tailed t-test was used in J. **P<0.01. Data are mean±s.e.m. Scale bars: 5 µm.
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