Planar cell movements and axial patterning preceding mammalian gastrulation

点击翻译按钮获取中文摘要

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.