Dissecting the dynamics of signaling events in the BMP, WNT, and NODAL cascade during self-organized fate patterning in human gastruloids
Dissecting the dynamics of signaling events in the BMP, WNT, and NODAL cascade during self-organized fate patterning in human gastruloids
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DOI：
10.1371/journal.pbio.3000498
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发表时间：
2019-10-01
期刊：
影响因子：
9.8
通讯作者：
Warmflash, Aryeh
中科院分区：
文献类型：
--
作者：
Chhabra, Sapna;Liu, Lizhong;Warmflash, Aryeh
在原肠胚形成过程中，多能性外胚层自组织形成3个胚层--内胚层、中胚层和外胚层，最终形成整个胚胎。几十年来对小鼠胚胎的研究表明，涉及骨形态发生蛋白（BMP）、WNT和NODAL通路的信号级联是原肠胚形成所必需的。在体内，WNT和NODAL配体在胚胎后部原肠胚形成位点附近表达，敲除这些配体导致原肠胚形成失败。这些数据导致了普遍的观点，即WNT和NODAL中的信号梯度是原肠胚形成过程中模式化的基础;然而，这些途径在空间和时间上的活动从未被直接观察到。在这项研究中，我们定量BMP，WNT，和NODAL信号动力学在体外模型的人原肠胚。我们的数据表明，BMP信号启动WNT和NODAL信号活动波，以恒定的速率向殖民地中心移动。使用一个简单的数学模型，我们表明，这种波浪状的行为是不一致的反应扩散为基础的图灵系统，表明没有稳定的信号梯度的WNT/NODAL。相反，最终的信号状态是均匀的，空间差异只产生于边界效应。我们进一步表明，WNT和NODAL信号的持续时间控制中胚层分化，而BMP信号的持续时间控制CDX 2阳性胚外细胞的分化。这些胚胎外细胞的身份一直存在争议，我们使用RNA测序（RNA-seq）获得它们的转录组，并显示它们与体内的人类滋养层细胞非常相似。BMP信号传导的结构域与这些滋养层样细胞的分化结构域相同;然而，WNT和NODAL都不形成直接映射到中胚层区域的空间模式，这表明中胚层分化动态地由多种信号的组合效应控制。我们将我们的数据合成为一个数学模型，该模型准确地概括了信号动力学，并预测了化学和物理扰动后的细胞命运模式。综上所述，我们的研究表明，在缺乏稳定的信号梯度的情况下，BMP、WNT和NODAL级联中的信号事件的动力学控制人类类胃体的命运模式。
During gastrulation, the pluripotent epiblast self-organizes into the 3 germ layers-endoderm, mesoderm and ectoderm, which eventually form the entire embryo. Decades of research in the mouse embryo have revealed that a signaling cascade involving the Bone Morphogenic Protein (BMP), WNT, and NODAL pathways is necessary for gastrulation. In vivo, WNT and NODAL ligands are expressed near the site of gastrulation in the posterior of the embryo, and knockout of these ligands leads to a failure to gastrulate. These data have led to the prevailing view that a signaling gradient in WNT and NODAL underlies patterning during gastrulation; however, the activities of these pathways in space and time have never been directly observed. In this study, we quantify BMP, WNT, and NODAL signaling dynamics in an in vitro model of human gastrulation. Our data suggest that BMP signaling initiates waves of WNT and NODAL signaling activity that move toward the colony center at a constant rate. Using a simple mathematical model, we show that this wave-like behavior is inconsistent with a reaction-diffusion-based Turing system, indicating that there is no stable signaling gradient of WNT/NODAL. Instead, the final signaling state is homogeneous, and spatial differences arise only from boundary effects. We further show that the durations of WNT and NODAL signaling control mesoderm differentiation, while the duration of BMP signaling controls differentiation of CDX2-positive extra-embryonic cells. The identity of these extra-embryonic cells has been controversial, and we use RNA sequencing (RNA-seq) to obtain their transcriptomes and show that they closely resemble human trophoblast cells in vivo. The domain of BMP signaling is identical to the domain of differentiation of these trophoblast-like cells; however, neither WNT nor NODAL forms a spatial pattern that maps directly to the mesodermal region, suggesting that mesoderm differentiation is controlled dynamically by the combinatorial effect of multiple signals. We synthesize our data into a mathematical model that accurately recapitulates signaling dynamics and predicts cell fate patterning upon chemical and physical perturbations. Taken together, our study shows that the dynamics of signaling events in the BMP, WNT, and NODAL cascade in the absence of a stable signaling gradient control fate patterning of human gastruloids.