Figure 4. Cytosolic V1 sectors are redistributed in rbc3α mutants. A, A′, Positive control for Atp6V1A immunolabeling (V1Aa and V1Ab cytosolic subunits) of yolk ionocytes in WT and mutant larvae. Scale bar, 20 μm. B, B′, Side view of WT and rbc3αQ850X lateral-line hair cells labeled with Alexa Fluor 488–phalloidin and V1A antibody. Labeling of V1A cytosolic subunits was enhanced at the base of WT but not mutant hair cells. Scale bar, 3 μm. C, Enhanced apical-to-basal ratio of V1A immunofluorescent signal in rbc3αQ850X mutants (WT, n = 15 neuromasts, 9 animals; rbc3αQ850X, n = 13, 8 animals; **** p < 0.0001, unpaired Student's t test). D, Average V1A fluorescent signal of whole neuromasts (WT, n = 15 neuromasts, 9 animals; rbc3αQ850X, n = 13, 8 animals; p = 0.57, unpaired Student's t test). E, E′, Transient expression of V0a1 subunit using Tg(myo6b:GFP–Atp6V0A1a) plasmid in ampullary hair cells at 3 dpf. Note strong basal signal in both WT and mutant hair cells. F, F′, Stable transgenic expression of V1Aa subunit in Tg(myo6b:GFP–Atp6V1Aa) larvae. Side view of L2 neuromast at 5 dpf. Note stronger basal signal in WT (F) than mutant (F′) hair cells (WT, n = 9 neuromasts, 9 animals; rbc3αQ850X, n = 5 neuromasts, 5 animals; p = 0.0004, unpaired Student's t test). Scale bar, 4 μm.