Hedgehog signaling in taste cell maintenance and regeneration

项目摘要/摘要 味觉是人类基本生存的关键组成部分，因为它是造成辨别的主要原因 摄取的物质维持我们的生活，以及其他有害于我们的健康的物质。即使是在现代 时代，随着安全和丰富的营养来源随处可见，味觉成为一种重要的临床 当它的丢失，通常与癌症治疗中使用的细胞毒治疗有关，导致不想要的 体重减轻，生活质量显著下降。这个问题出现了一个有趣的表现 在接受Hedgehog(HH)途径拮抗剂治疗的癌症患者中，他们经历了累积的味觉丧失 随着时间的推移，感觉，表明HH通路活动可能在维持味觉系统中发挥关键作用。一个 保持味觉的基础的另一个线索是外科手术去神经导致的140年前的观察 味蕾退化。最后，我们观察到味觉神经元及其投射显示脂质- 表面修饰了Sonic Hedgehog(Shh)编码的HH蛋白配体。这些观察结果加在一起 引出了这一提议中涉及的中心假设：神经元HH信号诱导并指定 舌上皮干细胞或前体细胞形成新的味觉感受器细胞的位置。 我们的建议针对的是TRC更换，以抵消在正常动态平衡期间TRC的周转，以及 化疗或HH途径导致近乎完全丧失时需要大规模再生 对抗性。这一假说还代表了一种新的生物学原理，即精确定位的递送 远端神经元突起的强大感应信号(HH)可以维持出生后的组织模式 (维持)或在严重损伤(再生)后的新生器官形成过程中施加正确的模式。至 确定神经元Shh信号如何支持TRC维持(目标1)，我们建议确定关键 Shh表达的神经元能够诱导TRCs从头开始的特征，决定了 神经元提供Shh信号的要求，并确定上皮细胞的潜在贡献 嘘，向TRC维修部发出信号。为了了解再生(目标2)，我们将用HH途径治疗小鼠 在消融TRC方面特别有效的拮抗剂，然后在恢复期跟踪TRC再生以 确定Hedgehog途径的活性是否受限，确定Shh信号的细胞呈现， 并找出其他可能有助于再生的线索。最后，我们将确定Shh的作用机制 通过神经元突起传递(目标3)，使用特殊标记的Shh蛋白并测试 在其他环境中对HH蛋白的释放起作用的其他已知因素。我们的研究结果将扩大我们的 对味觉器官动态平衡和感官再生的生物学理解，但也 应该有助于提高我们预防味觉丧失的能力，或促进接受细胞毒治疗的患者的味觉恢复 癌症治疗。

PROJECT SUMMARY/ABSTRACT Taste sensation is a critical component of basic human survival, as it contributes centrally to the discrimination of substances whose ingestion sustains us and others that are detrimental to our well-being. Even in modern times, with safe and abundant sources of nutrients all around us, taste sensation becomes a significant clinical issue when its loss, often associated with the cytotoxic treatments employed in cancer therapy, causes unwanted weight reduction and a significant decrement in quality of life. An intriguing manifestation of this problem occurs in cancer patients treated with a Hedgehog (Hh) pathway antagonist, who experience cumulative loss of taste sensation over time, suggesting that Hh pathway activity may play a critical in maintaining the taste system. An additional clue to the basis of taste maintenance is the 140 year-old observation that surgical denervation causes taste bud degeneration. Finally, we observe that gustatory neurons and their projections display the lipid- modified Hh protein ligand encoded by Sonic hedgehog (Shh) on their surface. These observations together lead to the central hypothesis addressed in this proposal: that a neuronal Hh signal induces and specifies the position of de novo taste receptor cell (TRC) formation from stem or progenitor cells of the lingual epithelium. Our proposal addresses TRC replacement to offset TRC turnover during ordinary homeostasis, as well as the wholesale regeneration required when near-complete loss is inflicted by chemotherapy or Hh pathway antagonism. This hypothesis also represents a new biological principle, namely, that precisely localized delivery of a potent inductive signal (Hh) by processes from distant neurons can sustain postnatal tissue pattern (maintenance) or impose correct pattern during de novo organ formation after severe injury (regeneration). To determine how neuronal Shh signaling supports TRC maintenance (Aim 1), we propose to identify the critical features that allow Shh-expressing neurons to induce TRCs de novo, determine the temporal characteristics of the requirement for neuronal provision of the Shh signal, and determine the potential contribution of epithelial Shh signal to TRC maintenance. To understand regeneration (Aim 2) we will treat mice with a Hh pathway antagonist that is particularly efficient in ablating TRCs, then track TRC regeneration during a recovery period to determine whether Hedgehog pathway activity is limiting, determine the cellular presentation of the Shh signal, and identify other cues that may contribute to regeneration. Finally, we will determine the mechanism of Shh delivery via neuronal processes (Aim 3) by using specially marked Shh protein and testing the contributions of other factors known to function in release of Hh protein in other settings. The results of our study will expand our biological understanding of taste organ homeostasis and of sensory organ regeneration generally, but also should help improve our ability to prevent loss of taste or facilitate its recovery in patients undergoing cytotoxic cancer therapy.