The Role of the Maternal Factors in Ascidian Development andEvolution

这个提议描述了用海鞘胚胎进行的实验，海鞘胚胎是已知的最简单的脊索动物胚胎。这些胚胎的发育方式与包括人类在内的其他脊索动物胚胎非常相似。海鞘的早期卵裂、轴形成和原肠胚形成的模式被很好地描述，许多胚胎学实验表明，卵中的母体因素在幼虫的组织中起重要作用。斯瓦拉博士的实验室使用了两种密切相关的海鞘物种，它们的幼虫表型非常不同，以分离和表征正常幼虫发育所必需的母体因素。他们分离出了三种新基因，这些基因存在于有尾蝌蚪幼虫的物种中，而不存在于无尾蝌蚪幼虫的物种中。其中两个基因可能是结合DNA并开启或关闭基因的转录因子，而另一个可能是参与细胞间通讯的信号分子。本提案中描述的实验将研究这些蛋白质在发育过程中可能发挥的作用，方法是用抗体表征这些蛋白质在卵子和胚胎中的定位，并检查可能的蛋白质-蛋白质相互作用。这些结果将深入了解母体蛋白在胚胎发育过程中如何参与发育过程和细胞规范。这个实验室的长期目标是在脊椎动物胚胎中找到类似的基因，看看它们在这些胚胎中可能起什么作用。

This proposal describes experiments done with ascidian embryos, the simplest chordate embryos known. These embryos develop in a very similiar manner to other chordate embryos, including humans. The patterns of early cleavage, axis formation and gastrulation are well described in ascidians and a number of embryological experiments have shown that maternal factors in the egg are important in specifying tissues in the larvae. Dr. Swalla's lab has used two closely related ascidian species with very different larval phenotypes to isolate and characterize maternal factors necessary for normal larval development. They have isolated three novel genes that are present in the species that has a tailed tadpole larva and are absent in the species that has a tailless larva. Two of these genes are likely to be transcription factors that bind DNA and turn genes off and on, while the other is likely to be a signalling molecule involved in cell-cell communication. The experiments described in this proposal will investigate the role these proteins may play in development by characterizing the localization of the proteins in the eggs and embryos with antibodies and by examining possible protein-protein interactions. These results will give insight into how maternal proteins may be involved in developmental processes and cell specification during embryonic development. A long term goal of this laboratory is to then find similiar genes in vertebrate embryos and see what their role might be in these embryos.