The Role of the Maternal Factors in Ascidian Development andEvolution

这项建议描述了用海鞘胚胎所做的实验，这是已知的最简单的脊索胚胎。这些胚胎的发育方式与包括人类在内的其他脊索类胚胎非常相似。早期卵裂、轴形成和原肠形成的模式在海鞘中得到了很好的描述，许多胚胎学实验表明，卵中的母体因素在指定幼虫组织的过程中起着重要作用。斯瓦拉博士的实验室使用了两种关系密切的海鞘物种，它们的幼虫表型截然不同，以分离和鉴定正常幼虫发育所需的母体因子。他们已经分离出三个新的基因，这些基因存在于有尾巴的蝌蚪幼虫的物种中，而没有出现在没有尾巴的幼虫的物种中。其中两个基因很可能是与DNA结合、开启和关闭基因的转录因子，而另一个很可能是参与细胞间通讯的信号分子。这项建议中描述的实验将通过用抗体表征这些蛋白质在鸡蛋和胚胎中的定位以及通过检查可能的蛋白质-蛋白质相互作用来研究这些蛋白质在发育中可能发挥的作用。这些结果将使人们深入了解母体蛋白如何参与胚胎发育过程和细胞规格。这个实验室的长期目标是在脊椎动物胚胎中找到相似的基因，并看看它们在这些胚胎中可能起到什么作用。

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.