Mild loss of Hensen's cells after deletion of Jag1 from pillar and Deiters' cells at 1 week of age. A, Experimental strategy. Fgfr3-iCreERT2::Jag1fx/fx (Jag1 CKO) and Jag1fx/fx (Ctrl) mice were injected with tamoxifen at P6/P7, and cochleae are analyzed at P13. B–D, Quantification of IHCs, OHCs, and individual SC subtypes (inner pillar cells to Hensen's cells) in the apical (B), middle (C), and basal (D) turns of the cochleae in Ctrl and Jag1 CKO mice at P13. Data are mean ± SEM; n = 4/group. **p < 0.01; ****p < 0.0001; two-way ANOVA followed by a Bonferroni post hoc test. DC1, Deiters' cell row 1; DC2, Deiters' cell row 2; DC3, Deiters' cell row 3; HeC, Hensen's cell; IPC, inner pillar cells; OPC, outer pillar cells.