Fig. 6.

p27^Kip1 is specifically downregulated among PCs/DCs during spontaneous HC regeneration in the neonatal mouse cochlea. (A-C‴) Representative confocal slice images with anti-S100a1 (red), anti-Sox2 (magenta), and anti-p27^Kip1 (cyan) antibodies used to investigate changes in the expression of the cell cycle inhibitor p27^Kip1 in SCs after HC damage (DMG). Controls (CTRL) for each time point were littermates that lacked either the Atoh1-CreER^TM or Rosa26^DTA allele (A-A‴). Atoh1-DTA mice were injected with tamoxifen (Tam) at P0/P1 to induce HC death and cochleae were collected at P2 or P4 (B-C‴). All Sox2-positive/p27^Kip1-negative cells observed were also S100a1-positive, which suggests that they were PCs and DCs. Scale bar: 25 µm. (D) Higher magnification image of the boxed region in C‴ showing a Sox2-positive/p27^Kip1-negative cell (white arrow). Scale bar: 5 µm. (E) A small number of Sox2-positive/S100a1-positive/p27^Kip1-negative PCs/DCs were detected at P2 and P4 after HC damage, whereas no p27^Kip1-negative cells were detected in controls at any age or outside the S100a1 region. ***P<0.001, determined using a one-way ANOVA with a Sidak's post-hoc test. Data are mean±s.e.m.; n=3-5. n.s., not significant.