背景:鸟类节点相当于两栖动物Spemann\的组织者,如它诱导第二轴的能力所示,细胞贡献,和基因表达,而鼠标的节点,显示有限的感应能力,被认为是空间分布信号的一部分。此外,小鼠节点的结构特性备受争议,而对其他哺乳动物的等效结构知之甚少。
结果:我们使用形态学和在胃泌成之前和期间选择的组织者基因的表达分析了猪中的节点和新出现的组织者。该节点是根据“四个季度模型”定义的,基于比较考虑。猪的节点显示多层,包括柱状上皮的致密结构,背侧的瓶状细胞,和腹侧间充质细胞。gosecoid(gsc)的表达,chordin,和brachyury,连同形态学,揭示了三个不同域的连续出现:原肠胚形成前体域,推定节点,和成熟的节点。此外,gsc在上胚层上皮形成之前显示腹侧表达结构域。
结论:我们的研究定义了猪中新出现的组织者等同物的形态和分子背景,并表明其功能的顺序发展。
BACKGROUND: The avian node is the equivalent of the amphibian Spemann\'s organizer, as indicated by its ability to induce a secondary axis, cellular contribution, and gene expression, whereas the node of the mouse, which displays limited inductive capacities, was suggested to be a part of spatially distributed signaling. Furthermore, the structural identity of the mouse node is subject of controversy, while little is known about equivalent structures in other mammals.
RESULTS: We analyzed the node and emerging organizer in the pig using morphology and the expression of selected organizer genes prior to and during gastrulation. The node was defined according to the \"four-quarter model\" based on comparative consideration. The node of the pig displays a multilayered, dense structure that includes columnar epithelium, bottle-like cells in the dorsal part, and mesenchymal cells ventrally. Expression of goosecoid (gsc), chordin, and brachyury, together with morphology, reveal the consecutive emergence of three distinct domains: the gastrulation precursor domain, the presumptive node, and the mature node. Additionally, gsc displays a ventral expression domain prior to epiblast epithelialization.
CONCLUSIONS: Our study defines the morphological and molecular context of the emerging organizer equivalent in the pig and suggests a sequential development of its function.