Our results are also consistent with another recent study, which failed to observe injury-evoked nuclear transport of YAP1 in the mouse utricle34. In addition to observing YAP1 in supporting cells, we also observed cytoplasmic YAP1 immunoreactivity in a subset Lifitegrast Lifitegrast of developing hair cells in the mouse utricle. ototoxic injury. In contrast, substantial YAP1 nuclear translocation was observed in the chicken utricle after streptomycin treatment in vitro and in vivo. Together, these data suggest that differences in Lifitegrast YAP1 signaling may partially account for the differing regenerative abilities of the avian vs. mammalian inner ear. (the diphtheria toxin receptor), thus permitting the selective ablation of Lifitegrast hair cells via systemic treatment with diphtheria toxin31,32. Treatment of mature Pou4f3-huDTR mice with a single 25?ng/gm injection of diphtheria toxin (DT) leads to partial loss of vestibular hair cells12,31,32. In our experiments, Pou4f3-huDTR and Pou4f3?+?/?+?(WT control) mice (4C6?weeks of age) received a single 25?ng/ml injection of DT, and utricles were examined after 7- and 14-days recovery. Fixed specimens were immunolabeled for myosin Vlla, Sox2 and YAP1, and imaged using confocal microscopy. Resulting data showed loss of myosin VIIa-labeled hair cells in the striolar and extrastriolar regions of Pou4f3-huDTR mice, relative to WT controls. However, this lesion did not lead to increased YAP1 nuclear translocation in the striolar or extrastriolar Tap1 regions of either the Pou4f3-huDTR or WT utricles at either time point (Fig.?4A,B). Open in a separate window Physique 4 Nuclear translocation of YAP1 was not observed after diphtheria toxin (DT)-mediated hair cell lesions. (A) Adult Pou4f3?+?/?+?and Pou4f3?+?/DTR mice were injected with a single dose of DT (25?ng/g i.p). After 7 (DT7) or 14 (DT14) days recovery, utricles were collected, fixed and immunolabeled for myosin VIIa (green), SOX2 (blue) and YAP1 (red). Confocal images of wholemount utricles from Pou4f3?+?/?+?(wild type control, at DT14) and Pou4f3?+?/DTR at DT7 and at DT14 are shown in the top row. Images from the hair cell region and supporting cell region are shown in the second and third rows, and fourth, and?fifth rows, respectively. Treatment with DT led to reduced hair cell numbers (green) and increased area of YAP1 positive (red) labeling in Pou4f3?+?/DTR mice?at DT14 and DT7, as compared to wild type controls. (B) Quantitative data on hair cell density after a single dose of DT (25?ng/g i.p). All data were obtained from 50 X 50?m regions within the lateral extrastriolar (L), striolar (S) and medial extrastriolar (M) regions of each utricle. There was a significant decrease in hair cell numbers at DT7 and DT14, compared to controls (p?