Fig. 4: Reduced levels of MYO7A at the UTLD and stereocilia base of Myo7a-ΔC mice.

a MYO7A immunoreactivity at the UTLD in WT and Myo7a-ΔC mice at P7 and P16. MYO7A is detected at the UTLD of Myo7a-ΔC IHCs, but the intensity is reduced compared with WT (scale bars: 1 μm). b MYO7A in the UTLD of Myo7a-ΔC mice decreased by 68% at P7 (p < 1e−3) and 58% at P16 (p < 1e−3) compared with WT. The fluorescence intensity of MYO7A puncta was normalized against a dark background near the UTLD staining in the same image and z-section. Mean normalized intensities of MYO7A at the UTLD, averaged per cell: P7: WT = 3.58 ± 0.51, Myo7a-ΔC = 1.28 ± 0.21, p = 2.73e−16; P16: WT = 3.59 ± 1.00, Myo7a-ΔC = 1.37 ± 0.23, p = 4.30e−05. N = number of cells. Numbers analyzed per genotype and age (UTLDs; cells; animals): WT, P7 (157; 20; 4), P16 (73; 10; 4). Myo7a-ΔC, P7 (62; 10; 4), P16 (35; 7; 4). c MYO7A immunoreactivity at the stereocilia base of IHCs of WT and Myo7a-ΔC at P7 and P16 (scale bars: 1 μm). d Quantification of MYO7A at the stereocilia base. MYO7A puncta were normalized against a dark background in the image. Mean normalized intensities of MYO7A at the base, averaged per cell: P7: WT = 5.09 ± 0.71, Myo7a-ΔC = 1.093 ± 0.068, p = 6.98e−15; P16: WT = 3.96 ± 1.54, Myo7a-ΔC = 1.23 ± 0.089, p = 3.35e−05. N = number of cells. Numbers analyzed per genotype and age (stereocilia bases; cells; animals): WT P7 (406; 18; 4), P16 (187; 13; 4); Myo7a-ΔC: P7 (64; 6; 4), P16 (79; 6; 4). p values in b and d were derived from two-tailed, unpaired t-tests. Boxplots show medians, 25th and 75th percentiles as box limits, and minima and maxima as whiskers. e HA-immunofluorescence resolved the membrane-adjacent localization of HA-MYO7A-C in the HA-Myo7a-C KI mice, as well as MYO7A enrichment at the predicted site of the UTLD and the stereocilia base (and tips in some cases). The inset shows the HA-tag signal at the UTLD at higher magnification (scale bar: 5 μm). Source data are provided in the Source Data file.