Mechanical Clocks During Fetal Development

项目总结 发展的关键在于时机。从受精卵到新生儿，胚胎发育就像一个 高度协调的刻板印象事件序列。该过程的每个阶段的顺序和时间， 包括组织形态发生的时间和祖细胞的分化，是构建 成熟的器官要及时出生。时间上的缺陷与先天出生缺陷以及 成人的慢性疾病，包括哮喘、肺气肿、肾功能衰竭和II型糖尿病。是什么控制着 发育的节奏--胚胎的中心节拍器--是生物学中的一大谜团。 到目前为止，只有少数分子计时器被发现，包括昼夜节律和节段。 时钟，两者都作为转录振荡器运行，由周期性激活的 细胞外生化刺激。然而，目前尚不清楚生物化学信号是如何通过 扩散可以将相隔很长距离的器官的发育速度结合在一起 胚胎。我们最近出人意料地发现，哺乳动物胚胎的形态发生速度 肺被来自腔内液体压力的机械力所缠绕，它控制着 整个器官的同步的上皮分支和平滑的肌肉收缩。这些发现表明 胎儿体内存在“机械钟”。因为流体压力是瞬间传递的 在遥远的组织之间，机械钟可以同步器官的发育速度， 允许在出生前协调成熟。在这里，我们建议研究肺，肾， 和胰腺发育，这些器官都是通过胚胎内部和周围的液体连接在一起的 通过分枝形态发生。我们将定义压力的大小如何控制扩散速度， 利用微流控方法进行分化和形态发生。我们还将确定振荡 压力诱导的信号通路，并研究流体力是如何在 远距离器官，以确保它们的发育速度相匹配。我们将结合芯片上器官的模型， 组织特异性报告动物、转基因基因敲除小鼠、单细胞转录组学和蛋白质组学，以及 定量时间推移成像分析，并与对人类患者样本和 夹带缺陷的小鼠模型。这项工作将揭示胎儿共享的机械环境是如何 器官允许它们在出生前及时协调地生长和成熟，这对设计新的 治疗与先天性缺陷和发育早熟有关的疾病的方法以及 成人的慢性病。

PROJECT SUMMARY Development is all about timing. From fertilized egg to newborn infant, embryonic development proceeds as a highly coordinated sequence of stereotyped events. The order and timing of each stage of the process, including the timing of tissue morphogenesis and differentiation of progenitor cells, are essential for building mature organs in time for birth. Defects in timing are associated with both congenital birth defects as well as chronic diseases in the adult, including asthma, emphysema, renal failure, and type II diabetes. What controls the tempo of development – the central metronome of the embryo – is one of the great mysteries of biology. Only a handful of molecular timers have been discovered to-date, including the circadian and segmentation clocks, both of which operate as transcriptional oscillators that are entrained by periodic activation of extracellular biochemical stimuli. However, it is unclear how biochemical signals that are transmitted by diffusion can couple the rates of development of organs that are separated by large distances within the embryo. We recently discovered unexpectedly that the rate of morphogenesis of the embryonic mammalian lung is entrained by mechanical forces from luminal fluid pressure, which controls the frequency of synchronized epithelial branching and smooth muscle contraction across the organ. These findings suggest the presence of a “mechanical clock” in the fetus. Because fluid pressure is transmitted instantaneously between distant tissues, a mechanical clock could synchronize the rates of development across organs, permitting coordinated maturation before birth. Here, we propose to investigate the coupling of lung, kidney, and pancreatic development, organs that are all connected by fluid within and around the embryo and that form via branching morphogenesis. We will define how the magnitude of pressure controls the rates of proliferation, differentiation, and morphogenesis using microfluidics approaches. We will also identify the oscillatory signaling pathways that are induced by pressure and investigate how fluid forces are transmitted between distant organs to ensure that their rates of development are coupled. We will combine organ-on-a-chip models, tissue-specific reporter animals, transgenic knockout mice, single-cell transcriptomics and proteomics, and quantitative time-lapse imaging analysis, and complement these with studies of human patient samples and mouse models of entrainment defects. This work will uncover how the shared mechanical environment of fetal organs permits them to grow and mature coordinately in time for birth, which is essential for designing new approaches to treat disorders associated with congenital defects and developmental prematurity, as well as chronic diseases in the adult.