Endocrine timing of the cell cycle in the zebrafish: The case of glucocorticoids

内分泌信号在正常生理和疾病中起着重要作用。我们所知的一个主要空白是它们的节律性，通常是脉冲释放模式如何影响体内生理靶点的时间，如细胞分裂周期。此外，对于这些信号系统在发育过程中如何成熟功能知之甚少。在这里，我们建议用糖皮质激素作为内分泌信号的一个例子来解决这些问题。我们将探索最近揭示的糖皮质激素在斑马鱼幼虫[1]中定时昼夜节律细胞周期进程中的作用的分子机制，作为一种模型生理读数。我们将使用一组生物传感器来监测完整动物的糖皮质激素信号活动和细胞周期进程，以了解肾上腺信号的动力学及其对细胞周期进程的影响。糖皮质激素信号将由糖皮质激素应答元件控制的荧光素酶报告基因来测量，细胞周期进程将由细胞周期调节因子Wee1启动子控制的荧光素酶报告基因来监测。生物传感器将使我们能够在发育过程中以及垂体功能中断的突变体中研究肾上腺信号的成熟和昼夜节律细胞周期动力学。最终，这些生物传感器系将成为筛选具有下丘脑-垂体-肾上腺轴功能紊乱和细胞增殖缺陷的突变体的有价值的工具。

Endocrine signals play crucial roles in normal physiology and disease. A major gap in our knowledge is how their rhythmic, often pulsatile release patterns impact on timing of their physiological targets in vivo, such as cell division cycles. Furthermore, relatively little is known about how these signalling systems mature functionally during development. Here, we propose to address these questions using glucocorticoids as an example of an endocrine signal. We will explore the molecular mechanisms underlying the recently revealed role of glucocorticoids in timing circadian cell cycle progression in zebrafish larvae [1] as a model physiological readout. We will use a set of biosensors to monitor glucocorticoid signalling activity and cell cycle progression in the intact animal to understand the dynamics of adrenal signals and their effect on cell cycle progression. Glucocorticoid signalling will be measured using a luciferase reporter under control of Glucocorticoid Response Elements, and cell cycle progression will be monitored using a luciferase reporter gene under control of the promoter of the cell cycle regulator Wee1. The biosensors will enable us to study the maturation of adrenal signalling and circadian cell cycle dynamics during development and in mutants with disrupted pituitary function. Ultimately, these biosensor lines will represent a valuable tool to screen for mutants with disrupted hypothalamic-pituitary-adrenal axis function and cell proliferation defects.