Figure 2. Architecture of the hearing organ in Clrn1^ex4–/– mice and Clrn1^ex4fl/fl Myo15-Cre^+/– mice.

(A–F) Hair bundle structure is affected in Clrn1^ex4–/– mice but not in Clrn1^ex4fl/fl Myo15-Cre^+/– mice. Throughout the spiral cochlea, the OHC hair bundles of Clrn1^ex4–/– mice are linear, wavy, and/or hooked in shape (B and E), contrasting with the V-shaped hair bundles in control (A and D) and Clrn1^ex4fl/fl Myo15-Cre^+/– (C and F) mice. Note that the upper image of IHCs in C is a crop of Supplemental Figure 3A (lower portion of P20 panel). Similar hair bundle abnormalities were observed along the entire cochlear axis between P12 and P25 (images representative of 12 mice). The stereocilia of the short row (colored in red) regressed entirely in most of the OHCs of P12 Clrn1^ex4–/– mice (E), but not in those of P20 Clrn1^ex4fl/fl Myo15-Cre^+/– mice (F). (G) The physical coupling between the tallest stereocilia of OHCs and the overlying tectorial membrane (TM) was preserved in both Clrn1^ex4–/– and Clrn1^ex4fl/fl Myo15-Cre^+/– mice, as shown by the presence of imprints of the stereocilia (white arrows) on the lower surface of the tectorial membrane. Scale bars: 1 μm.