Fig. 1.

HC degeneration and TUBB3 expression in outer but not inner or vestibular HCs of newborn GFI1 mutant ears. (A-C) Gfi1^cre/cre cochlear OHCs degenerate in a basal to apical gradient at P0 (A,C), whereas vestibular HCs persist (B) (n=6). (D,E) Inner hair cell (IHC) counts at P0 revealed an increase in IHCs between 8 and 32 kHz (D), as well as increased IHC doublets at 16 kHz (E) in the Gfi1^cre/cre cochlea (Gfi1^cre/+ n=3, Gfi1^cre/cre n=4). (F) Gfi1^cre/cre vestibular HCs possess thinner stereocilia bundles (n=3). (G) P0 vestibular HC counts revealed no significant difference in HC number between genotypes (n=3). (H) Positive TUNEL staining is present in the P0 Gfi1^cre/cre cochlea, which is indicative of OHC death by apoptosis, while no TUNEL staining is observed in the vestibular system (n=3). (I) Gfi1^cre/cre OHCs abnormally expressed the neuronal marker TUBB3 (n=3). Scale bars: 20 µm (A,C,E,H,I; cochlea); 50 µm (B,F,H,I; vestibule). Data are mean±s.d. *P<0.05, **P<0.01; ns, not significant. Statistical significance assessed using a two-tailed Welch's t-test.