Cells from the sensory macula of 2-week-old mouse utricles lose the capacity to close lesions, corresponding with a change in actin concentration. A, Phalloidin labeling of a P15 utricle cultured for 48 h after lesioning, demonstrating that the lesion had not closed. The sensory epithelium (SE) and the nonsensory epithelium (NSE) are labeled. B, Higher-magnification view of phalloidin labeling of actin in a P19 utricle cultured 24 h after lesioning showing that, although there was little contraction, there was a buildup of actin along the leading edge of the lesion (arrows). C, Phalloidin labeling of 2-week-old utricles cultured for 36 h after a lesion that extended out of the sensory epithelium into the nonsensory epithelium. Although the sensory epithelium had not closed in on the lesion, cells from the nonsensory epithelium migrated into the lesion (arrow). D–H, Cells in the sensory epithelium have enhanced cortical actin belts compared with cells in the nonsensory epithelium in mature utricles. D, A P0 utricle labeled with phalloidin, showing that the immature utricular epithelium had a comparable level of actin and thickness of the cortical belts between the sensory epithelium and the nonsensory epithelium. E, A P17 utricle labeled with anti-occludin shows that the concentration of occludin at the tight junction and thickness of the tight junctions are also comparable for cells in the sensory epithelium and nonsensory epithelium. F, A P17 utricle labeled with phalloidin reveals the sharp increase in labeling intensity and thickness of the cortical actin belts for the cells within the sensory epithelium compared with the cells in the nonsensory epithelium. G, Quantification of the ratio of labeling intensity for sensory epithelium compared with nonsensory epithelium for P0 phalloidin labeling, P17 occludin labeling, and P17 phalloidin labeling. H, Quantification of the junctional width for cells in the sensory epithelium and nonsensory epithelium for 10 cell junctions in the sensory epithelium and 10 cell junctions in the nonsensory epithelium per utricle for P0 phalloidin labeling (n = 5 utricles), P17 occludin labeling (n = 7 utricles), and P17 phalloidin labeling (n = 6 utricles). The width of the actin belts in the P17 sensory epithelium is significantly greater than the other junctional complexes (*p < 0.005).