Fig. 3: MYO7A-C is expressed primarily in IHCs and in a tonotopic gradient in OHCs, with decreasing expression toward the cochlear base.

a MYO7A and MYO6 immunoreactivity in apical and basal turns of organ of Corti of P5 Myo7a-ΔC and WT mice (scale bar: 20 μm). b MYO7A immunoreactivity was quantified in apical, middle, and basal turns by normalizing to MYO6 immunoreactivity. Compared with WT, MYO7A levels in Myo7a-ΔC mice were reduced by ~85% (p < 1e−4) in all IHCs, and by ~30% and 52% (p < 1e−3 and <1e−4) in middle and apical-turn OHCs. Each data point in b corresponds to a mean MYO7A/MYO6 immunofluorescence ratio (mean of 12 IHCs and 36 OHCs per organ and position). Error bars indicate SD. N (animals) = 5 in WT and 7 in Myo7a-ΔC. p values in b were derived from two-tailed, unpaired t-tests. c Design of the HA-Myo7a-C KI mouse. HA-tag was knocked-in after the ATG of Myo7a-C by CRISPR-mediated gene editing. d Organ of Corti of an HA-Myo7a-C KI mouse, stained with a HA-specific antibody. The white boxes indicate approximate positions of the apical and basal cochlear regions shown on the right. HA immunoreactivity, representing the expression of MYO7A-C, is strong in all IHCs. In OHCs, HA immunoreactivity is readily detected at the cochlear apex, but decreases toward the base (scale bars: 200 μm in whole organ of Corti image, 20 μm in magnified panels). e The genomic position from which the Myo7a promoter used in the Myo7a::Actin-GFP transgenic mouse is derived. f Actin-GFP signal and phalloidin reactivity in the organ of Corti of Myo7a::Actin-GFP transgenic mice at P6. The Actin-GFP signal was predominantly observed in the IHCs. Actin-GFP signal was detected at low levels in the apical OHCs, and decreased tonotopically toward the basal end of the cochlea (scale bar: 10 μm). Source data are provided in the Source Data file.