EMBRYONIC INDUCTION OF MESODERM AND NEURAL TISSUE

这里提出的工作的长期目标是理解 决定细胞命运的因素，包括分化和图案化 脊椎动物早期发育。特别注意归纳法。 神经组织。 最近，已有研究表明，多肽生长因子可作为形态因子。 或决定因素，因为它们将细胞的命运从外胚层改变为 非洲爪哇早期发育过程中的中胚层途径。两个胚胎 多肽生长因子、成纤维细胞生长因子和VGL蛋白是 参与中胚层诱导。也已知至少有一个其他人 需要因子来解释所有中胚层细胞类型 形成了。这另一个因素很可能是他转变的一部分 生长因子β家族，可能是XTC分泌的诱导因子 细胞，XTC-MIF。我们现在已经克隆了转化生长因子β基因的几个新成员 其中之一可能是XTC-MIF基因。我们建议 研究这些新的TGFβ基因在早期发育和发育过程中的表达 确定它们在中胚层和/或神经诱导中的作用。 该提议的第二个主要方面源于我们发现的一种神经 诱发因素。这种因子是从小鼠巨噬细胞系分泌的， 在非洲爪哇分离的外胚层细胞中诱导神经组织，这将 否则，只能形成具缘毛的表皮。经PIF处理的动物帽子 将诱导的背侧中枢神经系统和中胚层组织组织成清晰的轴线 具有前后两极。综上所述，这些发现表明 该PIF具有许多与Spemann组织者相关联的属性。 我们建议纯化PIF蛋白，克隆其非洲爪哇编码基因 对这种新型神经的功能和表达进行同源和研究 诱发因素。

The long term objective of the work proposed here is to understand the factors that specify cell fates, both differentiation and patterning, in early vertebrate development. Special attention is given to the induction of neural tissue. Recently, it has been shown that peptide growth factors act as morphogens or determinants in that they change the fates of cells from ectodermal to mesodermal pathways during early Xenopus development. Two embryonic peptide growth factors, fibroblast growth factor and the Vgl protein, are involved in mesoderm induction. It is also known that at least one other factor is needed to account for all the mesodermal cell types that are formed. This other factor is likely to be a member of he transforming growth factor beta family and may be the inducing factor secreted from XTC cells, XTC-MIF. We have now cloned several new members of the TGFbeta gene family, in Xenopus, one of which may be the XTC-MIF gene. We propose to study the expression these new TGFbeta genes in early development and determine their roles in mesodermal and/or neural induction. A second major aspect of the proposal stems from our discovery of a neural inducing factor. This factor, secreted from a murine macrophage cell line, induces neural tissue in isolated Xenopus ectodermal cells that would otherwise form only ciliated epidermis. Animal caps treated with PIF organize the induced dorsal CNS and mesodermal tissues into a clear axis with antero-posterior polarity. Taken together, these findings suggest that PIF has many of the properties associated with a Spemann organizer. We propose to purify the PIF protein, clone the gene encoding its Xenopus homologue and study the function and expression of this novel neural inducing factor.