Figure 7.

Overexpression of β-catenin expands and inhibits elongation of the sensory epithelium. A, When β-catenin was overexpressed in sensory progenitors at E12.5 in Sox2-CreER;β-catenin^flox(exon3) mice, the sensory epithelium expanded with extra hair cells in the midbasal region, but failed to extend to the apex by E17.5, when hair cells had nearly completely developed in a Cre-negative littermate. B, At high-magnification, in the midbasal region, all Atoh1-positive cells expressed myosin VIIa. In β-catenin expression mutants, the sensory epithelium was wider, but only some of the Atoh1-positive cells expressed myosin VIIa. C, When β-catenin overexpression was initiated at E13.5, the sensory epithelium also expanded and extended toward the apex by E17.5. D, Higher-magnification of B (overexpression of β-catenin) showed an expanded area between inner and outer hair cells. E, At P0 the sensory epithelium extended nearly to the apex when β-catenin overexpression was initiated at E13.5 but not at E12.5. F, When overexpression of β-catenin was initiated at E12.5, the difference in the length of the sensory epithelium was significant at E17.5 and P0 (p < 0.01), whereas it was shorter at E17.5 but similar to the Cre-negative littermate by P0 when initiated at E13.5 (p < 0.05 at E17.5). Scale bar, 100 μm.