Fig. 2.

Morphogenesis of the Foxg1 null inner ear. A,C,E: Foxg1 in heterozygotic animals is expressed in the entire presumptive cochlea, the inferior and superior vestibular ganglia, the spiral ganglion, the geniculate ganglia, utricle, saccule, and all canal cristae. There is weaker expression in the developing anterior and posterior canals (but not the horizontal canal), and in the endolymphatic duct. B,D,F: In the Foxg1 null mutant, the LacZ expression pattern is basically the same as in the wild-type at E11.5. E,F: Whereas the size of the cochlea and ganglia appear to be normal, there is reduced anterior–posterior extension of the canal plates and the posterior plates that would normally fuse to form the posterior canal (E), remains unfused (F). D: The cochlea shows a delay in spiraling. Additionally, the mutant shows LacZ expression in the horizontal canal, whereas there is no Foxg1 expression in the horizontal canal of the Foxg1 heterozygote. C–F: The Foxg1 heterozygotes show a distinct horizontal crista sensory patch (C,E) that is completely absent in Foxg1 null mice (D,F). Note the more extensive reaction in Foxg1 null mice that is likely due to the double expression of LacZ under Foxg1 promoter control. AC, anterior crista; PC, posterior crista; ED, endolymphatic duct; SVG, superior vestibular ganglion; IVG, inferior vestibular ganglion; GG, geniculate ganglion; Coch, cochlea; U, utricle; S, saccule; SpGl, spiral ganglion. Scale bar = 100 μm in all images, anterior is to the left, dorsal is up.