Barrow Jeffery R, Howell William D, Rule Michael, Hayashi Shigemi, Thomas Kirk R, Capecchi Mario R, McMahon Andrew P
Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
Dev Biol. 2007 Dec 1;312(1):312-20. doi: 10.1016/j.ydbio.2007.09.030. Epub 2007 Sep 26.
The establishment of anteroposterior (AP) polarity in the early mouse epiblast is crucial for the initiation of gastrulation and the subsequent formation of the embryonic (head to tail) axis. The localization of anterior and posterior determining genes to the appropriate region of the embryo is a dynamic process that underlies this early polarity. Several studies indicate that morphological and molecular markers which define the early AP axis are first aligned along the short axis of the elliptical egg cylinder. Subsequently, just prior to the time of primitive streak formation, a conformational change in the embryo realigns these markers with the long axis. We demonstrate that embryos lacking the signaling factor Wnt3 exhibit defects in this axial realignment. In addition, chimeric analyses and conditional removal of Wnt3 activity reveal that Wnt3 expression in the epiblast is required for induction of the primitive streak and mesoderm whereas activity in the posterior visceral endoderm is dispensable.
小鼠早期上胚层前后极性的建立对于原肠胚形成的起始以及随后胚胎（从头到尾）轴的形成至关重要。前后决定基因在胚胎适当区域的定位是一个动态过程，是这种早期极性的基础。多项研究表明，定义早期前后轴的形态学和分子标记首先沿椭圆形卵柱体的短轴排列。随后，就在原条形成之前，胚胎的构象变化使这些标记与长轴重新对齐。我们证明，缺乏信号因子Wnt3的胚胎在这种轴向重新对齐中存在缺陷。此外，嵌合分析和Wnt3活性的条件性去除表明，上胚层中Wnt3的表达是诱导原条和中胚层所必需的，而后侧脏内胚层中的活性则是可有可无的。
