Fig. 1.

Adult Foxg1 expression analysis using LacZ. Strong Foxg1 expression is seen in the cochlea, saccule, utricle, and canal cristae. Weaker Foxg1 expression is seen in the canals, particularly near the ampullae of the cristae; and is strongest at the inner and outer curvatures. In the utricle, an expression gradient can be seen from stronger to weaker expression in the neuronal to abneuronal portions, respectively. A: There is a faint gradient in the cochlea with the base being less stained than the apex. B: The horizontal crista sensory epithelium is outlined to show that the Foxg1 expression is limited to the supporting cells of the sensory epithelia. C: An overview of the cochlea shows very intense expression in the spiral ganglion, the inner spiral sulcus, and the organ of Corti except for the cell-free tunnel of Corti. D,E: Radial sections through the cochlea show intense staining in the Reissner’s membrane, spiral limbus, and inner spiral sulcus (below the tectorial membrane). The inner hair cells are strongly labeled, whereas outer hair cells are faintly labeled. All supporting cells are labeled, including border cells, inner and outer pillar cells, Deiter’s cells, and Hensen’s cells. The outer spiral sulcus, or Claudius’ cells are strongly labeled, but the stria vascularis is strikingly devoid of staining, as is the otic mesenchyme and the basilar membrane. F: The vestibular ganglion shows Foxg1 in all neurons, but the intensity is variable. G: The utricle of the adult shows staining in some hair cells and all supporting cells on the neuronal side with a rapid decrease of expression on the abneuronal side. A,C,D,H: All spiral ganglion neurons demonstrate Foxg1 expression to varying degrees. PC, posterior crista; HC, horizontal crista; AC, anterior crista; U, utricle; S, saccule; B, base; A, apex; SpGl, spiral ganglion; SpSl, spiral limbus; OC, organ of Corti; RM, Reissner’s membrane; SV, stria vascularis; TM, tectorial membrane; SL, spiral limbus; BM, basilar membrane; IHC, inner hair cell; OHC, outer hair cell; BC, border cell; IP, inner pillar; TC, tunnel of Corti; OP, outer pillar; DC, Deiter’s cell; HC, Hensen’s cell; HCs, hair cells; SCs, supporting cells. Scale bars = 100 μm in A–D,F–H, 10 μm in E.