Figure 1. c-Jun expression and S73 phosphorylation during development. a, At P0, tympanic border cells and scattered cells of the lateral wall and Reissner’s membrane express c-Jun. Inset reveals that this expression is not linked with c-Jun S73 phosphorylation, shown in the tympanic border cell region. b, At P6, c-Jun is expressed in the greater epithelial ridge and in Schwann cells of the cochlear nerve (arrow). b', Schematic representation of the organ of Corti at P6: greater epithelial ridge (red), inner hair cell (blue), outer hair cells (cyan), inner pillar cell (yellow), outer pillar cell (orange), Deiters’ cells (green), and Hensen cell (gray). c, c-Jun S73 is phosphorylated in the greater epithelial ridge at P6. Arrowheads mark outer hair cells. c', An adjacent, ApopTag-stained section shows apoptotic fragments in the same area. d, At P0, the annular ligament of stapes shows c-Jun S73 phosphorylation. d', Apoptotic cells are not present in this structure, as evidenced by cleaved caspase-3 staining. e, At P12, c-Jun is expressed in Deiters’ cells of the organ of Corti and in the root cell area of the lateral wall. e', Schematic representation of the cytoarchitecture of the mature organ of Corti: inner border cells (magenta). Other color codes as in b'. AL, Annular ligament of stapes; apop, ApopTag-staining; casp, cleaved caspase-3; DC, Deiters’ cell; IP, inner pillar cell; OC, organ of Corti; OP, outer pillar cell; TBC, tympanic border cell; RC, root cell; RM, Reissner’s membrane; S, stapes; SV, stria vascularis; GER, greater epithelial ridge. Scale bar: (in d') a, a', b, d, d', e, 40 µm; (in d') c, c', 10 µm.