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

摘要 原肠发育是早期胚胎发育的阶段，在这一阶段，体型是 已经成立了。以小鼠为模型，已证实哺乳动物的原肠发育 主要受骨形成蛋白、成纤维细胞生长因子、WNT和结节信号通路的调节以及对这些信号通路的破坏 途径可导致发育缺陷或早期胚胎死亡，其发病方式如下 不孕不育。然而，目前尚不清楚细胞如何解释多条信号通路来 特定的细胞命运决定。此外，在老鼠身上的发现不能直接与人类相比 发展。例如，在囊胚期破坏成纤维细胞生长因子信号会导致 内脏内胚层在小鼠体内发育，但在人类体内不发育。人多能干细胞 是研究原肠形成的理想模型系统，因为它们模拟了原肠形成的许多方面 原肠作用，并允许高通量、定量分析和时间分辨实验 体外培养。利用微图案化hPSC原肠形成模型和定向原始条纹样细胞 分化模型，我的数据表明较高的成纤维细胞生长因子/ERK信号活性是空间上的 仅限于PSLCs和阻止成纤维细胞生长因子信号转导的功能实验 PSLC分化及WNT3配体表达下调。基于此，我的 最重要的假设是，成纤维细胞生长因子/ERK信号在空间和时间上受 成纤维细胞生长因子配体和硫酸肝素蛋白聚糖(HSPG)调节剂的表达及其作用 与WNT和Node上游的BMP平行，以创建组合信号模式，从而诱导 不同的细胞命运结果。我将通过1)确定成纤维细胞生长因子的活性如何来检验这一假设 受成纤维细胞生长因子配体和热休克蛋白G调节剂的空间和时间调节，2)解剖 在体外原肠形成过程中细胞命运获得背后的多种信号活动的动态。

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.