Fig. 6. The inner ear phenotype in Gfi1 mutant mice. (A,C,E,G,I) are Gfi1 wild-type (+/+) mice and (B,D,F,H,J) are Gfi1 null (-/-) mice. (A,B) Hematoxylin and Eosin (H&E) morphological stains of the organ of Corti at P14. Note the development of the organ of Corti with one inner (red arrow) and three outer (green arrows) hair cells in the wild type, but its complete degeneration in the mutant section. (C,D) Hematoxylin and Eosin morphological stains of the saccule at 5 months of age. Note the presence of hair cells with stereocilli in both the wild-type and mutant. However, the mutant saccule has disorganized layering of the hair and support cells. (E-J) The progressive degeneration of the cochlear ganglion neurons in the mutant mice. (E-H) Sections stained with anti-activated-caspase-3 (C3) as a marker of apoptosis (brown cells) and counterstained with Hematoxylin. Arrows in E, F and H indicate activated-caspase-3-positive cells. (E,F) P7 mice. Note similar cell densities and levels of apoptosis in both samples. (G,H) P21 mice. Note that by P21 we see a slightly lower cell density in the mutant as well as a high level of apoptosis in the mutant that is not present in the wild-type mouse. (I,J) 5-month-old mice. Sections stained with Hematoxylin and Eosin.