Cell cycle in development and regeneration of the inner ear

哺乳动物感觉毛细胞的丧失会导致永久性耳聋，因为再生不会 发生.再生能力的丧失与细胞内专门的支持细胞的无能有关。 Corti器官开始分裂以响应毛细胞死亡。我们采取了一种发展的方法， 这个问题我们的希望是，通过彻底了解器官细胞的过程， Corti在胚胎发生过程中停止分裂，我们将深入了解为什么再生不会发生。做 因此，我们希望提供工具和目标，以治疗性介入治疗失聪问题。 在Corti器官的发育过程中，细胞增殖的控制与 细胞分化和模式化的过程（Ruben，1968）。我们已经证明， 激酶抑制剂p27 Klp 1需要定时这种协调。在p27 Klp 1突变小鼠中，细胞周期退出是 延迟，导致多余的细胞，毛细胞组织的有序模式的破坏， 耳聋（Chen和Segil，1999年）。 尽管p27 Klp 1丰度被广泛认为是在转录后水平上调节的， 通过控制蛋白质周转，我们的结果表明p27 Klp 1的转录调控在很大程度上， 尽管不是全部，但它决定了成熟器官中细胞的数量。额外 初步数据表明，Notch通路信号传导可能是调节p27转录的关键因素 在Corti器官形成期间。在具体目标1中，我们分析了Notch信号在空间和细胞周期中的作用。 Corti器胚胎发生过程中p27 Klp 1转录的时间调节。 尽管p27 Klp 1转录调控的重要性，我们已经观察到在Skp 2突变体中， 小鼠的细胞周期出口和Corti器官结构也有缺陷。Skp 2是SCF-泛素的一部分 连接酶复合物，参与调节p27 Klp 1蛋白周转。在具体目标2中，我们讨论了 p27 Klp 1的转录后调控机制。 最后，在具体目标3和4中，我们通过研究p27 Klp 1直接解决再生问题。 出生后支持细胞的调节。我们最近开发了一种技术， 并在体外培养。在这样做的过程中，我们发现围产期支持 细胞保留了重新进入细胞周期和分裂的能力，而来自P14小鼠的支持细胞则不能 这样做. P14支持细胞下调p27 Kip 1能力的变化是导致P14表达下调的部分原因。 细胞分裂受阻导致再生障碍。这个特定的目的是研究分子 我们假设p27调节的年龄依赖性变化的基础是缺乏再生 在哺乳动物的内脏。

Loss of sensory hair cells in mammals results in permanent deafness because regeneration does not occur. The loss of regenerative ability is tied to the inability of the specialized supporting cells within the organ of Corti to begin dividing in response to hair cell death. We have taken a developmental approach to this problem. Our hope is that by thoroughly understanding the process by which the cells of the organ of Corti stop dividing during embryogenesis, we will gain insight into why regeneration does not occur. In doing so, we hope to provide tools and targets for therapeutic intervention into the problem of deafness. During development of the organ of Corti, control of cell proliferation is tightly coordinated with the process of cell differentiation and patterning (Ruben, 1968). We have shown that the cyclin-dependent kinase inhibitor p27Klp1 is required for timing this coordination. In p27Klp1 mutant mice, cell cycle exit is delayed, leading to supernumerary cells, a disruption of the orderly pattern of hair cell organization, and deafness (Chen and Segil, 1999). Although p27Klp1 abundance is widely believed to be regulated at the post-transcriptional level through control of protein turnover, our results indicate that transcriptional regulation of p27Klp1 is largely, though not entirely, responsible for the determining the number of cells in the mature organ. Additional preliminary data indicates that Notch pathway signaling may be a key player in regulating p27 transcription during organ of Corti formation. In Specific Aim 1 we analyze the role of Notch signaling in the spatial and temporal regulation of p27Klp1 transcription during embryogenesis of the organ of Corti. In spite of the importance of p27Klp1 transcriptional regulation, we have observed that in Skp2 mutant mice, there is also a defect in cell cycle exit and organ of Corti structure. Skp2 is part of the SCF-ubiquitin ligase complex that is involved in regulating p27Klp1 protein turnover. In Specific Aim 2 we address the role of post-transcriptional mechanisms in the regulation of p27Klp1. Finally, in Specific Aims 3 and 4 we address the problem of regeneration directly, by studying p27Klp1 regulation in postnatal supporting cells. We have recently developed techniques that allow us to purify postnatal supporting cells and grow them in vitro. In doing so, we have discovered that perinatal supporting cells retain the capacity to reenterthe cell cycle and divide, while supporting cells from P14 mice are unable to do so. Changes in the ability of P14 supporting cells to down-regulate p27Kip1 are partly responsible for the block to cell division that results in the lack of regeneration. This specific aim investigates the molecular basis for the age-dependent change in p27 regulation that we hypothesize underlies the lack of regeneration in the mammalian innerear.