Fig. 3. Hair cells are dramatically increased in Dll1/Jag2 double mutant cochleae, whereas supporting cells are only modestly reduced. (A-D) Myosin VIIa (red), p27^kip1 (green) and DAPI (blue nuclear stain) immunostained sections from E18.5 Dll1^hyp/-Jag2^-/- mutant and control cochleae. Supporting cells are clearly still present in Dll1^hyp/-Jag2^-/- mutant cochleae, as shown by the p27^kip1-stained cells. However, some p27^kip1-stained cells (presumably Deiter's cells) appeared to be missing in some sections (C,D, arrows). (E-H) E18.5 cochleae processed for in situ hybridization using the indicated probes. Expression of -tectorin or ß-tectorin in the various supporting cell populations did not appear to differ between controls and mutants, with the exception of ß-tectorin expression in Deiter's cells (H), which appears to be disorganized and reduced. (I) Hair and supporting cell counts from sections, as shown in A-D. Sections from three ears were counted for each group, either control or Dll1^hyp/-Jag2^-/-. Controls were either wild type, or Dll1 or Jag2 single heterozygotes. Counts of both hair cells and supporting cells were significantly different between Dll1^hyp/-Jag2^-/- mutant and control cochleae (^*P<0.001, Student's t-test). However, the increase in hair cells did not equal the supporting cell losses (P<0.0001; one-way ANOVA). d, Deiter's cells; h, Hensen's cells; Ko, Koelliker's organ; iPh, inner phalangeal cells; p, pillar cells. Scale bars: in D, 50 µm for A-D; in H, 50 µm for E-H.