Fig. 3. Generation and progressive degeneration of hair cells in the organ of Corti of Barhl1-null mice. (A,B) RNA in situ hybridization analysis of coronal ear sections shows similar levels of Math1 expression in cochlear hair cells (arrows) between Barhl1^+/+ and Barhl1^–/– mice at P0. (C,D) Similar levels of myosin VIIa immunoreactivity are seen in cochlear hair cells between Barhl1^+/– and Barhl1^–/– mice at P6. (E-P) ß-galactosidase staining of Barhl1^+/– and Barhl1^–/– whole-mount organs of Corti: note the disorganization of outer hair cells (OHC) in the apex of the mutant at P6 (F), followed by the loss of many of these cells from the apical and middle turns by P19 (G,K) and the degeneration of the majority of these cells by P59 (H,L). The outer hair cells in the basal turn, however, show no obvious degeneration by P59 in the mutant (M-P). Similarly, the inner hair cells (IHC) remain normal up to P59 (E-P). Scale bar in P: 100 µm in A,B; 25 µm in C,D; 18.75 µm in E-P.

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