Dynamics of Delta/Notch signaling on endomesoderm segregation in the sea urchin embryo
Dynamics of Delta/Notch signaling on endomesoderm segregation in the sea urchin embryo
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DOI：
10.1242/dev.044149
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发表时间：
2010-01-01
期刊：
影响因子：
4.6
通讯作者：
McClay, David R.
中科院分区：
文献类型：
--
作者：
Croce, Jenifer C.;McClay, David R.
内胚层是许多动物发育早期内胚层和中胚层的共同祖先。在海胆胚胎中，Delta/Notch途径是该组织多样化所必需的，两个早期转录因子GCM和FoxA分别在中胚层和内胚层表达。在这里，我们提供了导致内胚层分离的卵裂的详细谱系分析，并在谱系的背景下检查了这种细胞命运二分法的三个已知调节因子的表达模式和调控关系。我们观察到内胚层分离最早发生在孵化囊胚期。在此阶段之前，GCM和FoxA在同一细胞中共表达，而在孵化时，这些基因在两个不同的细胞群中被检测到。GCM在大多数植物内胚层后代细胞中仍有表达，而FoxA在这些细胞中表达下调，并在上述相邻细胞中激活。最初，Delta只在微粒中表达，大多数植物内胚层细胞后代表达GCM并成为中胚层所必需的。我们的实验表明，在这些细胞中GCM表达独立于进一步的Delta输入之前，需要连续的Delta输入超过两次切割(或大约2.5小时)。因此，本研究对海胆胚胎发育过程中内胚层分离的时间机制和分子动力学以及Delta/Notch通路在调节中胚层命运中的作用模式提供了新的见解。
Endomesoderm is the common progenitor of endoderm and mesoderm early in the development of many animals. In the sea urchin embryo, the Delta/Notch pathway is necessary for the diversification of this tissue, as are two early transcription factors, Gcm and FoxA, which are expressed in mesoderm and endoderm, respectively. Here, we provide a detailed lineage analysis of the cleavages leading to endomesoderm segregation, and examine the expression patterns and the regulatory relationships of three known regulators of this cell fate dichotomy in the context of the lineages. We observed that endomesoderm segregation first occurs at hatched blastula stage. Prior to this stage, Gcm and FoxA are co-expressed in the same cells, whereas at hatching these genes are detected in two distinct cell populations. Gcm remains expressed in the most vegetal endomesoderm descendant cells, while FoxA is downregulated in those cells and activated in the above neighboring cells. Initially, Delta is expressed exclusively in the micromeres, where it is necessary for the most vegetal endomesoderm cell descendants to express Gcm and become mesoderm. Our experiments show a requirement for a continuous Delta input for more than two cleavages (or about 2.5 hours) before Gcm expression continues in those cells independently of further Delta input. Thus, this study provides new insights into the timing mechanisms and the molecular dynamics of endomesoderm segregation during sea urchin embryogenesis and into the mode of action of the Delta/Notch pathway in mediating mesoderm fate.