Figure 4.

Pou4f3 deletion from OHCs in sexually mature mice leads to elevated ABR thresholds and progressive OHC loss. (A) Schematic for the experimental design using Prestin-Pou4f3cKO mice to delete Pou4f3 from OHCs at 8 weeks (wks) of age. Open arrows indicate post-tamoxifen (post-Tam) timepoints when OHC loss was assessed. (B) At 2 weeks after Pou4f3 deletion, there was a significant elevation in ABR thresholds in Prestin-Pou4f3cKO mice compared to their control littermates at all frequencies tested [N = 6; significant main effect of genotype, F_(1,40) = 350.4, p < 0.0001]. Asterisks indicate comparisons between genotypes at each frequency based on a Bonferroni-corrected post-hoc test. (C–E″) Representative confocal images from control (C–C″) and Prestin-Pou4f3cKO (D–E″) cochleae. HCs in the control cochleae and IHCs in the Prestin-Pou4f3cKO cochleae remained intact (myosin VIIa, green) and had nuclear expression of POU4F3 (magenta). Analysis at 2 and 6 weeks after Pou4f3 deletion showed progressive loss of OHCs in Prestin Cre-Pou4f3cKO cochleae over time. The remaining OHCs at 2 weeks post-Tam expressed POU4F3 in their cytoplasm. (F) Quantification of OHC loss in control and Prestin-Pou4f3cKO cochleae (N = 3) between 1 and 6 weeks post-Tam. There was a significant main effect of time [F_(4,10) = 29.01, p < 0.0001]; cochlear turn [F_(2,20) = 13.88, p = 0.0002]; and an interaction between time and cochlear turn [F_(8,20) = 3.68, p = 0.0085]. Differences from control within each cochlear turn are indicated by the asterisks based on a Tukey's-corrected post-hoc test. Green asterisks are p values for the apical turn and red asterisks are p values for the basal turn. Black asterisks were used when the p value was the same for two or three turns. Data are presented as mean ± SEM. **p < 0.01 and ****p < 0.0001. Comparisons across time post-Tam and across cochlear turns within the same genotype are presented in Supplementary Table 5. Scale bar = 20 μm.