Fig. 3

pH regulators of the spindle cell and cell-type-specific pH-dependent genes. A: Schematic model of pH regulation in the SC. The SC isolates the endolymph (E) from the intrastrial space (IS). Endolymph pH (7.5) is maintained by pendrin (Cl⁻/HCO₃⁻) and by AE2, NHEs, ENac across the apical membrane of the SC, together with carbonic anhydrase (CA13) (AE2, anion exchanger 2; ENac, Epithelial Na⁺ channel; NHEs, Na⁺/H⁺ exchangers; TWIK, two-pore-domain K⁺ channel; T, tight junction). B: Violin plot showing the gene expression of pH regulators, including anion exchangers (Slc4a2), Na⁺/H⁺ exchanger (Slc9a4), carbonic anhydrase (Car13) (* indicates novel findings with pendrin expression). C-D: Colocalization of pendrin and intracellular carbonic anhydrase 13 in the inner ear. C: Representative confocal images of transversal cochlea section showing the colocalization of pendrin (green) and CA13 (red). The high magnification shows the colocalization in the SC, SP, and OS (OS, outer sulcus; RC, root cells; SC, spindle cells; SLg, spiral ligament; SP, spiral prominence; blue, nuclei; grey, F-actin). D: Diagram showing the line analysis (Y-axis, fluorescence intensity; X-axis, distance along the region of interest (ROI); SC; SP; OS). E: Bar plots of pH-dependent downregulated (blue) genes in SC/RC from Slc26a4^−/− mice compared to Slc26a4^+/+ mice. Note: One gene (Otogl) is highly expressed in RC; the other five genes are expressed in SC. F: Bar plot of downregulated (blue) and upregulated (red) genes in the IMC from Slc26a4^−/− mice compared to Slc26a4^+/+ mice. Note: These genes are highly expressed in IMC.