THE ROLE OF GROWTH-FACTORS IN EMBRYONIC INDUCTION IN XENOPUS-LAEVIS
THE ROLE OF GROWTH-FACTORS IN EMBRYONIC INDUCTION IN XENOPUS-LAEVIS
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DOI：
10.1002/mrd.1080320209
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发表时间：
1992-06-01
影响因子：
2.5
通讯作者：
REBAGLIATI, MR
中科院分区：
文献类型：
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作者：
DAWID, IB;TAIRA, M;REBAGLIATI, MR
所有动物，特别是脊椎动物胚胎中体型的建立，都依赖于细胞间的相互作用。在两栖动物卵裂和囊胚阶段，来自植物区的信号诱导赤道区成为中胚层。两种类型的肽生长因子已被外植体培养实验证明在中胚层诱导中是活跃的。首先，存在成纤维细胞生长因子（FGF）的几种同种型，包括aFGF、bFGF和hst/kFGF。FGF诱导腹侧，但不是最背侧，中胚层组织的水平; bFGF及其mRNA，和FGF受体及其mRNA，存在于胚胎中。因此，FGF可能在中胚层诱导中发挥作用，但不太可能是体内唯一的诱导剂。第二，转化生长因子-β（TGF-β）家族的成员。TGF-β 2和TGF-β 3在诱导中具有活性，但最强的诱导因子是TGF-β的远亲，名为激活素A和激活素B，它们能够诱导所有类型的中胚层。一个重要的问题涉及在中胚层诱导过程中极性的建立。虽然青蛙胚胎动物半球的所有区域都有能力通过中胚层分化对激活素作出反应，但只有包括靠近赤道的细胞的外植体形成沿着背腹和前后轴具有一些组织的结构。这些观察结果表明，在囊胚动物半球的细胞已经在一定程度上极化，虽然诱导剂需要使这种极性explicit.How诱导因素影响响应组织的分化？解决这个问题的一种方法是寻找诱导后的基因表达，特别是同源异型盒基因等调控位点的激活。几个含有同源框的基因，包括Mix.1，Xhox 3，X1 Hbox 1和X1 Hbox 6，goosecoid和一类新的基因Xlim的成员，被激活的诱导因子在胚胎中具有不同的表达模式。调控基因的差异表达可能控制着胚胎发生过程中不同组织的有序形成。
Establishment of the body pattern in all animals, and especially in vertebrate embryos, depends on cell interactions. During the cleavage and blastula stages in amphibians, signal(s) from the vegetal region induce the equatorial region to become mesoderm. Two types of peptide growth factors have been shown by explant culture experiments to be active in mesoderm induction. First, there are several isoforms of fibroblast growth factor (FGF), including aFGF, bFGF, and hst/kFGF. FGF induces ventral, but not the most dorsal, levels of mesodermal tissue; bFGF and its mRNA, and an FGF receptor and its mRNA, are present in the embryo. Thus, FGF probably has a role in mesoderm induction, but is unlikely to be the sole inducing agent in vivo. Second, members of the transforming growth factor-beta (TGF-beta) family. TGF-beta-2 and TGF-beta-3 are active in induction, but the most powerful inducing factors are the distant relatives of TGF-beta named activin A and activin B, which are capable of inducing all types of mesoderm. An important question relates to the establishment of polarity during the induction of mesoderm. While all regions of the animal hemisphere of frog embryos are competent to respond to activins by mesoderm differentiation, only explants that include cells close to the equator form structures with some organization along dorsoventral and anteroposterior axes. These observations suggest that cells in the blastula animal hemisphere are already polarized to some extent, although inducers are required to make this polarity explicit.How do inducing factors affect the differentiation of the responsive tissue? One approach to this question has been to look for gene expression in response to induction, especially the activation of regulatory loci like homeobox genes. Several homeobox-containing genes including Mix.1, Xhox3, X1Hbox1, and X1Hbox6, goosecoid and members of a new class of genes named Xlim, are activated by inducing factors with different patterns of expression in the embryo. Differential expression of regulatory genes probably controls the formation of distinct tissues in an orderly pattern during embryogenesis.