Molecular analysis of early body plan formation in lancelet embryos

研究了中华小血管原肠胚至神经胚期wnt7、wnt8、bmp2/4、brachyury、hnf3-β的表达规律。其中，与脊椎动物相比，bmp2/4表现出特定的表达模式。由于在脊椎动物中，小细胞中bmp2/4表达的区域与基因被抑制表达的区域相对应，因此该基因可能在这种动物的前特异性身体形成中起基本作用。其他基因在表达模式上与其脊椎动物同源基因相似。这些基因的空间表达模式表明，早期小囊胚有两个不同的前后区域，每个区域在不同的分子机制下发育。这两个不同的发育领域可能与三段式体腔系统有关，三段式体腔系统被认为是后口动物的基本身体计划。为了研究母体分子在早期合子基因的模式表达中的功能，我们筛选了更多的es， β-catenin蛋白，结蛋白，Tbrain/eomes (Tbr/eomes)， FGF受体mRNA。虽然它们的分子空间格局有其特殊性，但在第一次卵裂开始前或开始时，它们首先向动物极周围移动或聚集，然后向植物性移动或传播。它们中的一些在分裂的卵裂球之间不对称地分布。卵子和胚胎在第一次卵裂时的微管分布显示出类似的模式，表明母体因素与微管之间存在机械关系。LiCl处理影响β-catenin、Tbr/eomes和微管分布的事实支持了微管在受精后母体因子分布中的作用。背侧特异性基因，otx， goosecoid和lim3，在与脊椎动物一样的LiCl处理时改变了它们的表达模式。然而，经过处理的胚胎仍然形成背腹和左右极性。这些结果表明，小包膜胚胎在最初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极性是在第一次卵裂期间建立的。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