Figure 2.

Pou4f3 deletion from OHCs at hearing onset causes elevated ABR thresholds and significant OHC loss. (A) Schematic for the experimental design using Prestin-Pou4f3cKO mice to delete Pou4f3 from OHCs at 2 weeks of age. Open arrows indicate post-tamoxifen (post-Tam) timepoints when OHC loss was assessed. (B) At 4 weeks (wks) 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) = 428.1, 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). However, many OHCs were missing in Prestin-Pou4f3cKO cochleae at 1 and 4 weeks after Pou4f3 deletion. Most of the remaining OHCs at 1 week 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 cochlear turn [F_(2,20) = 43.81, p < 0.0001]; time [F_(4,10) = 49.21, p < 0.0001]; and an interaction between time and cochlear turn [F_(8,20) = 3.832, p = 0.0070]. 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, blue asterisks are p values for the middle 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, ***p < 0.001, and ****p < 0.0001. Comparisons across time post-Tam and across cochlear turns within the same genotype are presented in Supplementary Table 3. Scale bar =20 μm.