Molecular analysis of early body plan formation in lancelet embryos

研究了WNT7、WNT8、BMP2/4、Brachyury、HNF3-β在原肠胚至神经胚期的表达模式。其中，BMP2/4与脊椎动物相比，表现出独特的表达模式。由于BMP2/4在小柳条中的表达区域与其在脊椎动物中表达被抑制的区域相对应，因此该基因可能在脊椎动物的前特异体的形成中发挥基本功能。其他基因在表达模式上与它们的脊椎动物同源基因相似。这些基因的空间表达模式表明，早期的小柳叶胚胎在前后方向有两个不同的区域，每个区域都在不同的分子机制下发育。为了研究母体分子在早期合子基因模式表达中的作用，我们筛选了母体分子…更多的ES、β-连环蛋白、结节蛋白、脑/Eomesodermin(TbR/eomesodermin)、成纤维细胞生长因子受体(FGFR)被鉴定出来。尽管它们的分子空间格局表现出各自的特异性，但在第一次卵裂开始之前或期间，它们首先移动到动物极点或聚集在动物极点附近，然后在植物中移动或扩散。其中一些细胞在分裂的卵裂球之间不对称地分布。在第一次卵裂过程中，微管在卵子和胚胎中的分布显示出类似的模式，这表明母体因素与微管之间存在力学关系。氯化锂处理影响了β-连环蛋白、TbR/Eome和微管的分布，这支持了微管在受精后母体因子的分配中的作用。脊椎动物的背部特异基因OTX、Goosecid和lim3在LiClAS处理后改变了它们的表达模式。然而，处理后的胚胎仍然建立了背腹和左右两极。这些结果表明，柳条胚胎在最初的发育过程中利用了一组类似的分子，但与脊椎动物不同，母体分子的分布模式表明，胚胎的极性是在第一次卵裂时建立的。较少

Expression patterns of wnt7, wnt8, bmp2/4, brachyury, hnf3-β were studied from the gastrula to neurula stage in Chinese lancelets. Of them, bmp2/4 shows a specific expression pattern compared with that in vertebrates. Since regions where bmp2/4 is expressed in lancelets correspond to the region where the genes are inhibited their expression in vertebrates, this gene may play an basic function in anterior specific body formation in this animal. The other genes are similar to their vertebrate cognates in their expression pattern. The spatial expression pattern of these genes suggests that the early lancelet embryo has two distinct regions anteroposteriorly, each of which develops under different molecular mechanisms. The two distinct developmental domains may be related to the tripartite coelomic system that has been proposed as a basic body plan of deuterostomes.To investigate function of maternal molecules in patterning expression of earliest zygotic genes, we screened maternal molecul … More es, β-catenin protein, nodal, Tbrain/eomesodermin (Tbr/eomes), FGF receptor mRNA have been identified. Although spatial pattern of their molecules show their own specificity, they first move to or are accumulated around the animal pole before or during the onset of the first cleavage, and then move or spread vegetally. Some of them become distributed asymmetrically between the cleaving blastomeres. Distribution of microtubules in eggs and embryos during the first cleavage shows a similar pattern, suggesting mechanical relationships between maternal factors and microtubules. The fact that LiCl treatment affects distribution of β-catenin, Tbr/eomes and microtubules supports a role of microtubules in distribution of the maternal factors after fertilization. Dorsal specific genes, otx, goosecoid and lim3, modify their expression pattern when treated with LiCl as in vertebrates. However, treated embryos still establish dorsoventral and left-right polarities. These results suggest that the lancelet embryo utilizes a similar set of molecules during the initial development but in different way from vertebrates, the distribution pattern of maternal molecules suggests that embryonic polarity is established during the first cleavage. Less