Cellular, Molecular And Genetic Analysis Of Neural Fate In Zebrafish Embryos

Notch信号对斑马鱼侧线系统细胞命运和形态发生的调控 侧线神经节的感觉神经支配神经丘中的感觉毛细胞。它们共同构成了鱼类表面感觉系统的一部分，可以检测水流。神经乳突是典型的感觉器官，其发育和形态发生与果蝇眼睛中的小眼和哺乳动物耳朵的毛细胞等多种感觉器官具有显着的相似性。 后侧线原基（pLLp）是约一百个细胞的凝聚性集合。它在斑马鱼躯干和尾部的皮肤下向尾部迁移，周期性地从其尾端沉积神经瘤。迁移的pLLp包含3-4个处于不同成熟阶段的前神经乳头。当它们成熟时，感觉毛细胞在前神经肥大的中心被指定。支持细胞，也作为祖细胞的池，包围着毛细胞。当它们成熟时，前神经乳头形成中心定向的上皮突起。最后，成熟的前神经乳头从迁移的pLLp的尾端沉积，侧线神经节的感觉神经支配感觉毛细胞。随着神经肥大细胞的成熟，神经肥大细胞周围的祖细胞有助于形成额外的感觉毛细胞。 了解a）新的前神经乳头是如何在pLLp的前端启动的，B）感觉毛细胞是如何在这些细胞簇的中心被指定的，c）它们是如何形成中心定向的上皮细胞的，d）它们是如何从迁移的pLLp的尾端沉积的，以及，e）在斑马鱼胚胎的非常容易接近的侧线系统中，是什么调节了pLLp的尾部迁移，提供了一个有吸引力的背景下，了解更广泛的机制，调节器官发生在发育中的胚胎。它被证明是一个特别有吸引力的系统，了解不同的信号通路的功能是如何整合的，以及如何规范的细胞命运和发育器官内的形态发生是协调的。 先前的研究表明，由于稳定的前神经乳从其尾端沉积，新的前神经乳的形成是由位于迁移的pLLp的前端的Wnt依赖性FGF信号传导中心启动的。该FGF信号中心启动atoh 1a表达，Notch介导的侧向抑制限制atoh 1表达至成熟前神经乳头内的中央细胞。我们现在已经表明，中央atoh 1a在调节FGF信号传导中起着至关重要的作用，在迁移pLLp尾端的成熟神经瘤内。Atoh 1a表达驱动FGF配体如FGF 10的表达，同时抑制其受体FGFR 1的表达。通常，atoh 1a表达的Notch信号传导依赖性限制允许成熟神经瘤内受限FGF信号传导中心的自组织，因为中心FGF表达细胞激活其表达FGFR 1的邻居中的FGF信号传导。然而，当Notch信号转导失败时，太多的细胞表达atoh 1a。它们开始表达FGF并关闭其受体FGFR 1的表达。这最终导致FGF信号传导失败、Wnt信号传导不受调节和迁移pLLp的解体。 我们已经开发了计算机模型来可视化FGF，Wnt和Notch信号系统之间的相互作用如何调节侧线系统的自组织。计算建模说明了FGF、Wnt和Notch信号系统之间的相互作用以及趋化因子受体的差异调节如何调节pLLp的细胞命运、形态发生和迁移。该模型预测了负反馈在侧线系统的自组织中所起的关键作用。我们正在进行实验来测试计算机模型的预测。

Notch signaling regulates cell fate and morphogenesis in the zebrafish lateral line system Sensory nerves of the lateral line ganglion innervate the sensory hair cells in the neuromasts. Together they form a part of a sensory system on the surface of fish that detects water flow. The neuromasts are archetypical sense organs whose development and morphogenesis has remarkable similarities to diverse sensory organs like ommatidia in the Drosophila eye and hair cells of the mammalian ear. The posterior lateral line primordium (pLLp) is a cohesive collection of about a hundred cells. It migrates caudally under the skin in the zebrafish trunk and tail periodically depositing neuromasts from it trailing end. The migrating pLLp contains 3-4 proneuromasts at various stages of maturation. As they mature a sensory hair cell is specified at the center of the proneuromast. Support cells, which also serve as pool of progenitors, surround the hair cell. As they mature the proneuromasts form center-oriented epithelial rosettes. Eventually, mature proneuromasts are deposited from the trailing end of the migrating pLLp and sensory nerves of the lateral line ganglion innervate the sensory hair cells. The surrounding progenitor cells in the neuromast contribute to formation of additional sensory hair cells as the neuromasts mature. Understanding how a) new proneuromasts are initiated at the leading end of the pLLp, b) how sensory hair cells are specified at the center of these cells clusters, c) how they form center-oriented epithelial rosettes, d) how they are deposited from the trailing end of the migrating pLLp and, e) what regulates caudal migration of the pLLp, in the very accessible lateral line system of zebrafish embryos, provides an attractive context to understand the broader mechanisms regulating organogenesis in the developing embryo. It is proving to be an especially attractive system for understanding how the function of distinct signaling pathways is integrated and how specification of cell fate and morphogenesis within a developing organ is coordinated. Previous studies showed that as stable proneuromasts are deposited from its trailing end, formation of new proneuromasts is initiated by Wnt-dependent FGF signaling center at the leading end of the migrating pLLp. This FGF signaling center initiates atoh1a expression and Notch-mediated lateral inhibition restricts atoh1 expression to a central cell within maturing proneuromasts. We have now shown that the central atoh1a plays a critical role in regulating FGF signaling within maturing neuromasts at the trailing end of the migrating pLLp. Atoh1a expression drives expression of FGF ligands like FGF10, while inhibiting expression of its receptor FGFR1. Normally, the Notch-signaling dependent restriction of atoh1a expression allows the self-organization of a restricted FGF signaling center within maturing neuromasts as the central FGF expressing cell activates FGF signaling in its neighbors that express FGFR1. However, when Notch signaling fails, too many cells express atoh1a. They begin to express FGF and shut off expression of its receptor, FGFR1. This eventually leads to failure of FGF signaling, unregulated Wnt signaling and disorganization of the migrating pLLp. We have developed computer models to visualize how interactions between the FGF, Wnt and Notch signaling systems regulate the self-organization of the lateral line system. Computational modeling illustrates how interaction between the FGF, Wnt and Notch signaling systems and differential regulation of chemokine receptors could regulate cell fate, morphogenesis and migration of the pLLp. The modeling predicts a key role played by negative feedback in the self-organization of the lateral line system. We are carrying out experiments to tests predictions of the computer models.