Twisted gastrulation loss-of-function analyses support its role as a BMP inhibitor during early Xenopus ernbryogenesis
Twisted gastrulation loss-of-function analyses support its role as a BMP inhibitor during early Xenopus ernbryogenesis
复制标题
DOI：
10.1242/dev.00709
复制
发表时间：
2003-10-01
期刊：
影响因子：
4.6
通讯作者：
Chang, CB
中科院分区：
文献类型：
--
作者：
Blitz, IL;Cho, KWY;Chang, CB
BMP 信号在发育和成人的多种事件的调节中发挥着重要作用。在羊膜动物中，如两栖动物非洲爪蟾，BMP 促进腹侧规范，而在 Spemann 组织体中表达的脊索蛋白和其他 BMP 抑制剂在该区域作为背侧内中胚层的建立和/或维持中发挥作用。反过来，chordin 的活性又受到分泌的蛋白水解酶 BMP1 和 Xolloid 的调节。最近，我们和其他人发现扭曲原肠胚形成蛋白 (TSG) 是一种可溶性 BMP 调节剂，通过改变脊索蛋白活性发挥作用。在果蝇、爪蟾和斑马鱼中的过表达和遗传分析以及体外生化研究表明 TSG 可能充当 BMP 拮抗剂；但也有证据表明 TSG 可能促进 BMP 信号传导。在这里，我们报告使用功能丧失方法检查 TSG 在非洲爪蟾早期发育中的体内功能。我们表明，使用反义 TSG 吗啉代寡核苷酸 (MO) 减少 TSG 表达会导致中度头部缺陷。这些缺陷可以通过不能被 MO 抑制的 TSG 以及 BMP 拮抗剂 cordin 和 noggin 来挽救。此外，虽然在早期原肠胚中原肠胚形成的开始和标记基因的表达均不受影响，但背侧标记基因表达减少，以牺牲中晚期原肠胚阶段开始的腹侧标记基因表达扩展为代价。 TSG-MO 和 Chd-MO 也合作强烈抑制头部形成。最后，我们注意到，TSG 功能的丧失导致动物帽和腹侧边缘区组织对脊索蛋白 BMP 抑制功能的反应性发生变化，这一结果意味着脊索蛋白可能需要 TSG 活性才能在这些发育环境中有效抑制 BMP。这些数据与生物化学和过表达研究相结合，表明 TSG 在调节 Chordin 的 BMP 抑制活性的效力中发挥着重要作用，并且 TSG 和 Chordin 共同作用来调节早期青蛙胚胎的背前部发育程度。
BMP signals play important roles in the regulation of diverse events in development and in the adult. In amniotes, like the amphibian Xenopus laevis, BMPs promote ventral specification, while chordin and other BMP inhibitors expressed dorsally in the Spemann's organizer play roles in establishment and/or maintenance of this region as dorsal endomesoderm. The activities of chordin are in turn regulated by the secreted proteolytic enzymes BMP1 and Xolloid. Recently, we and others have identified the protein twisted gastrulation (TSG) as a soluble BMP modulator that functions by modifying chordin activity. Overexpression and genetic analyses in Drosophila, Xenopus and zebrafish together with in vitro biochemical studies suggest that TSG might act as a BMP antagonist; but there is also evidence that TSG may promote BMP signaling. Here we report examination of the in vivo function of TSG in early Xenopus development using a loss-of-function approach. We show that reducing TSG expression using antisense TSG morpholino oligonucleotides (MOs) results in moderate head defects. These defects can be rescued both by a TSG that cannot be inhibited by the MO, and by the BMP antagonists chordin and noggin. Furthermore, while neither the onset of gastrulation nor the expression of marker genes are affected in early gastrulae, dorsal marker gene expression is reduced at the expense of expanded ventral marker gene expression beginning at mid to late gastrula stage. TSG-MO and Chd-MOs also cooperate to strongly repress head formation. Finally, we note that the loss of TSG function results in a shift in tissue responsiveness to the BMP inhibitory function of chordin in both animal caps and the ventral marginal zone, a result that implies that the activity of TSG may be required for chordin to efficiently inhibit BMPs in these developmental contexts. These data, taken together with the biochemistry and overexpression studies, argue that TSG plays an important role in regulating the potency of chordin's BMP inhibitory activity and TSG and chordin act together to regulate the extent of dorsoanterior development of early frog embryos.