Figure 5. Morphological characteristics of cells in utricles 18 days after transduction with ATOH1.

(A) Many cells across the epithelium bear elongated microvillar-like projections from their apical surface. Scale bar: 5 µm. (B, C) Cells with dense cluster of apical projections possess a single thicker, kinocilium-like projection from the centre of the cell surface (arrowed). Scale bars: 1 µm. (D) Thin projections on cells expressing myosin VIIa (red) and GFP contain actin (blue). Scale bar: 2 µm. (E,F) Thin sections of cells in utricle in which SEM showed cells with dense clusters of apical projections in panel A, and (G,H) in a utricle that showed large numbers of myosin VIIa labelled cells after immunolabelling similar to the utricle shown in Figure 3 panel F. In cells with numerous, microvillar projections, nuclei are located towards the apical (luminal) surface and have approximately cylindrical cell bodies, similar to hair cells, but some (panels E and H) have thinning basal extensions, reminiscent of supporting cells converting to hair cells. Scale Bars: 2 µm.