Planar cell movements and axial patterning preceding mammalian gastrulation

良好平衡的细胞增殖和迁移是胚胎或其身体部位形成特定形状的基本先决条件。这些过程的分子机制在许多生物的不同发育阶段都有很好的描述，但在原肠胚形成之前，细胞行为的两个方面仍然不明确，尤其是哺乳动物胚胎。原肠胚形成不可逆转地固定了基本的身体计划。哺乳动物具有独特的初始轴向分化序列，实际上可能具有增殖和迁移的新特征和组合。本项目利用兔胚胎母细胞的植入后期、表面位置和扁平结构，在原位原肠胚形成之前，在视频显微镜下分析所有背细胞层（外胚层）的细胞运动。细胞运动模式将与细胞外基质分子、Wnt和节点信号级联成员的表达模式进行比较，这些分子已知调节细胞运动（例如，在平面细胞极性通路中）。以胚胎椎间盘前缘为标志，利用Wnt信号级联的修饰剂，分析单细胞或细胞片运动或细胞分裂平面的变化。此外，将使用标记基因（如ANF和Brachyury）分析轴向模式的实验结果，即前分化与后分化。这些结果可能有助于确定早期哺乳动物发育的核心机制。

Well balanced cellular proliferation and migration are basic prerequisites for the development of the specific shape of an embryo or of its body parts. Molecular mechanisms of these processes are well described in many organisms at various developmental stages, but immediately preceding gastrulation, which irrevocably fixes the basic body plan, both aspects of cellular behaviour are still ill-defined, especially for the mammalian embryo. With their unique sequence of initial axial differentiation, mammals may in fact employ novel characteristics and combinations of proliferation and migration. The present project uses the late implantation and the superficial position and flat architecture of the embryoblast in the rabbit to analyse videomicroscopically all cell movements in the dorsal cell layer (epiblast) immediately prior to gastrulation in situ. Patterns of cellular movement will be compared with the expression patterns of extracellular matrix molecules and of members of the Wnt and nodal signalling cascades, which are known to regulate cell movements (in the planar cell polarity pathway, for example). Using the anterior margin of the embryonic disc as a landmark and agents modifying the Wnt signalling cascades, changes of single cell or cell sheet movements or of cellular division planes will be analysed. In addition, experimental outcomes on axial patterning, i.e. anterior vs. posterior differentiation, will be analysed using marker genes such as ANF and Brachyury. The results may help to define mechanisms central to early mammalian development.