ROLE OF MAMALIAN FASTS IN EMBRYONIC TGF BETA SIGNALING

生长因子中的TGFbeta超家族成员也受到牵连。在广泛的生物学过程中，包括抑制体细胞组织中的细胞过度分裂和指定胚胎发生期间的细胞命运。我们已经在非洲爪哇早期胚胎中发现了一种新的转录因子FAST-1，它与转化生长因子β信号转导途径的上游成分相互作用，激活特定的转化生长因子β反应启动子。在非洲爪哇，FAST-1是早期胚胎基因计划的关键调节因子。我们现在计划研究哺乳动物FAST-1同源基因在调节早期胚胎转录程序中的作用。在初步实验中，我们克隆了小鼠和人类FAST-1同源物，发现它们与Smads和激活素反应启动子元件特异结合，非洲爪哇FAST-1也是如此。我们还发现，小鼠的FAST，像非洲爪哇FAST-1一样，主要在胚胎发育的早期表达。我们现在计划研究哺乳动物的FAT-1在调节正常和转化细胞的早期胚胎基因程序中的作用。首先，我们将研究哺乳动物FAST的表达以及人和鼠FAST偶联到TGFβ超家族配体下游的信号转导的特异性。然后我们将研究FAST Inc.细胞的异位表达是如何改变对TGFbetas的转录反应的。具体地说，我们将检验这一假设，即FAST是早期胚胎细胞表达早期中胚层标记的能力的重要组成部分，以响应TGFbetas。我们将利用FAST信号主要抑制物的异位表达，以及小鼠FAST在ES细胞中的同源重组敲除，以测试FAST是否对早期胚胎中胚层基因程序的表达响应TGFβ刺激是必需的。我们还将研究转化生长因子β/快速信号通路的抑制剂如何影响聚集的ES或DMSO处理的EC细胞分化为中胚层的能力。这些实验将阐明TGFbetas如何调节胚胎和胚胎后组织中不同的细胞反应，以及胚胎基因表达在胚胎干细胞分化中的作用。

Members of the TGFbeta superfamily of growth factors are implicated . in a vast range of biological processes, including the inhibition of cell peroliferation in somatic tissues and the specification of cell fate during embryogenesis. We have identify a novel transcription factor in early Xenopus embryos, FAST-1, which interacts with upstream components of the TGFbeta signal transduction pathway to activate specific TGFbeta responsive promoters. In Xenopus, FAST-1 is a critical regulator of the early embryonic gene program. We now plan to examine the role of mammalian FAST-1 homologs in the regulation of the early embryonic transcriptional program. In preliminary experiments we have cloned mouse and human FAST-1 homologs and found that they bind specifically to Smads and to an activin responsive promoter element, as does Xenopus FAST-1. We also find that mouse FAST, like Xenopus FAST-1, is expressed primarily during early embryogenesis. We now plan to examine the role of mammalian FAT-1 in the regulation of the early embryonic gene program in normal and transformed cells. First, we will examine the expression of mammalian FASTs and the specificity of coupling of mouse and human FAST to signal transduction downstream of TGFbeta superfamily ligands. We will then examine how ectopic expression of FAST inc ells which normally lack it alters transcriptional responses to TGFbetas. Specifically, we will test the hypothesis that FAST is an important component of the competence of early embryonic cells to express early mesodermal markers in response to TGFbetas. We will us the ectopic expression of dominant inhibitors of FAST signaling, as well as the knockout of mouse FAST by homology recombination in ES cells, to test whether FAST is necessary for the expression of early embryonic mesodermal gene program in response to TGFbeta stimulation. We will also examine how inhibitor of the TGFbeta/FAST signaling pathway affects the ability of aggregated ES or DMSO-treated EC cells to differentiate into mesoderm. These experiments will elucidate how TGFbetas regulate distinct cellular response in embryonic and post-embryonic tissues, and the role of the expression of embryonic genes in the differentiation of embryonal stem cells.