Figure 5.

Pou4f3 deletion at both neonatal and adult ages causes HC death by apoptosis. (A–D″) Representative confocal images from control (A–A″, C–C″) and Atoh1-Pou4f3cKO (B–B″) or Prestin-Pou4f3cKO (D–D″) cochleae 5 days after deletion of Pou4f3 at P0/P1 or one week after deletion of Pou4f3 at 4 weeks (wks) of age respectively. IHCs and OHCs were stained using myosin VIIa [green, (A–B″)] or the OHC-specific marker prestin [green, (C–D″)]. TUNEL staining (red) was used to identify apoptotic cells. No TUNEL staining was observed in control cochleae. However, many IHCs and OHCs from Atoh1-Pou4f3cKO cochleae and OHCs from Prestin-Pou4f3cKO cochleae were TUNEL-positive (arrows). (E, F) Quantitative real-time PCR analysis of the mRNA transcripts for the Pou4f3 target genes, Gfi1 and Lhx3, as well as the pro-apoptotic genes, p53, Bad, Bak1 and Bax. Samples were analyzed 5 days after deletion of Pou4f3 at P0/P1 using Atoh1-Pou4f3cKO mice or 1 week after deletion of Pou4f3 at 4 weeks of age using Prestin-Pou4f3cKO mice. Data are expressed as fold change (mean ± SEM) from control. Each gene was compared to its own control using a Student's t-test. N = 8–10. *p < 0.05, **p < 0.01, ***p < 0.001. Scale bar = 20 μm.