Dynamics of FGF and its integration with other pathways during human germ layer differentiation

摘要 原肠胚形成是早期胚胎发育的阶段，在此期间， 确立了习使用小鼠作为模型，已经确定哺乳动物原肠胚形成 主要受BMP、FGF、WNT和NODAL信号通路调节， 途径可导致发育缺陷或早期胚胎死亡， 不孕然而，目前尚不清楚细胞如何解释多种信号通路， 具体的细胞命运决定。此外，小鼠的研究结果不能直接与人类进行比较。 发展例如，在胚泡阶段FGF信号传导的破坏导致在胚胎发育中的缺陷。 小鼠内脏内胚层的发育，但在人类中没有。人多能干细胞（hPSC） 是研究原肠胚形成的理想模型系统，因为它们模拟了原肠胚形成的许多方面， 原肠胚形成，并允许高通量，定量分析和时间分辨实验， 体外使用微图案化hPSC原肠胚形成模型和定向原始条纹样细胞 分化模型，我的数据表明，更高的FGF/ERK信号转导活性是空间上的 仅限于PSLC和阻断FGF信号传导的功能性实验， PSLC分化以及WNT 3配体表达下调。基于此，我 总体假设是FGF/ERK信号传导在空间和时间上受 FGF配体和硫酸肝素蛋白聚糖（HSPG）调节剂的表达，并在 与WNT和NODAL上游的BMP平行，以产生诱导 不同的细胞命运我将通过1）确定FGF活性是如何影响 在空间和时间上受FGF配体和HSPG调节剂调节，2）剖析 在体外原肠胚形成过程中细胞命运获得的多种信号传导活动的动力学。

Abstract Gastrulation is the stage of early embryonic development during which the body plan is established. Using the mouse as a model, it has been established that mammalian gastrulation is primarily regulated by BMP, FGF, WNT, and NODAL signaling pathways and disruption of these pathways can lead to developmental defects or early embryonic lethality which ay infest as infertility. However, it remains unclear how cells interpret multiple signaling pathways to make specific cell fate decisions. Moreover, findings in mice cannot directly be compare to human development. For example, disruption of FGF signaling at blastocyst stage leads to defects in visceral endoderm development in mice but not in human. Human pluripotent stem cells (hPSCs) have been an ideal model system to study gastrulation because they mimic many aspects of gastrulation and allow for high throughput, quantitative analysis and time resolved experiments in vitro. Using micropatterned hPSC gastrulation model and directed primitive streak like cell differentiation model, my data suggests that higher FGF/ERK signaling activity is spatially restricted to PSLCs and functional experiments that block FGF signaling results in a failure of PSLC differentiation as well as downregulation of WNT3 ligand expression. Based on this, my overarching hypothesis is that FGF/ERK signaling is spatially and temporally regulated by expression of FGF ligands and heparin sulfate proteogylcan (HSPG) modulators and act in parallel to BMP upstream of WNT and NODAL to create combined signaling patterns that induce different cell fate outcome. I will test this hypothesis by 1) determining how FGF activity is spactially and temporally regulated by FGF ligands and HSPG modulators, 2) dissecting the dynamics of multiple signaling activity underlying cell fate acquisition during in vitro gastrulation.