Hedgehog signaling in taste cell maintenance and regeneration

项目总结/摘要 味觉是人类基本生存的重要组成部分，因为它对辨别 这些物质的摄入维持了我们的生命，而其他物质则对我们的健康有害。即使在现代 随着安全和丰富的营养来源在我们周围，味觉成为一个重要的临床 当其损失时，通常与癌症治疗中采用的细胞毒性治疗有关， 体重减轻，生活质量显著下降。这个问题的一个有趣的表现是， 在用Hedgehog（Hh）通路拮抗剂治疗的癌症患者中， 随着时间的推移，Hh通路的活性可能在维持味觉系统中起关键作用。一个 关于味觉维持的另一条线索是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- 修饰的Hh蛋白配体编码的声波刺猬（Shh）在其表面上。这些观察加在一起 导致本提案中提出的中心假设：神经元Hh信号诱导并指定 舌上皮干细胞或祖细胞从头味觉受体细胞（TRC）形成的位置。 我们的建议涉及TRC替换，以抵消TRC营业额在普通稳态，以及 当化疗或Hh途径造成几乎完全丧失时，需要大规模再生 对抗这一假说也代表了一个新的生物学原理，即精确定位的传递 一个强有力的诱导信号（Hh）的过程，从遥远的神经元可以维持出生后的组织模式 （维持）或在严重损伤后的从头器官形成期间施加正确的模式（再生）。到 确定神经元Shh信号如何支持TRC维持（目标1），我们建议确定关键的 这些特征使得Shh表达神经元能够从头诱导TRCs，决定了TRC的时间特征。 神经元提供Shh信号的要求，并确定上皮细胞的潜在贡献。 嘘信号呼叫TRC维修中心。为了理解再生（目标2），我们将用Hh途径治疗小鼠， 在消融TRC中特别有效的拮抗剂，然后在恢复期间跟踪TRC再生， 确定Hedgehog途径活性是否是限制性的，确定Shh信号的细胞呈递， 并识别其他可能有助于再生的线索。最后，我们将确定Shh的机制 通过使用特别标记的Shh蛋白和测试的贡献， 已知在其它环境中在Hh蛋白释放中起作用的其它因素。我们的研究结果将扩大我们的 对味觉器官内稳态和感觉器官再生的生物学理解， 应该有助于提高我们的能力，以防止失去味觉或促进其恢复患者接受细胞毒性 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.