Evolution of Developmental Processes Governing Head Formation

在过去的10-15年里，人们对调节胚胎发育为功能动物的基因和过程有了大量的了解。积累的知识中最有趣的一个方面是，一组共同的调控基因涉及到一组共同的或相关的机制，这些机制是迄今为止研究的后生动物的许多发育过程的基础。这些共同的特征提出了有趣而重要的问题：这些基因在进化过程中出现的时间有多早？它们在后生动物中已经存在了吗？他们参与了什么样的发展机制和发展过程？在动物进化过程中，早期发明的机制和过程在多大程度上得以保存？解决这些问题的一种方法是研究这些基因及其在生物体内的功能，这些生物属于在后生动物进化过程中非常早期出现的动物群体，比如刺胞动物，其成员包括水母、海葵和淡水水螅。其中，水螅是特别有用的，因为发育过程（模式的形成、增殖的控制和几种细胞类型的分化）是很好的理解。此外，许多已知的调节许多脊椎动物和无脊椎动物发育事件的基因也已被分离出来，并部分地在水螅中被表征。这项工作的总体目标是确定水螅头部发育的基因和机制是否与脊椎动物和昆虫头部发育的基因和机制相似。一个这样的基因已经被发现。作为水螅的同系物，它是水螅家族的一员，已经被鉴定并证明与水螅头部的特殊结构——触手的发育有关。也有证据表明，Dlx和Emx家族的同源物存在于水螅或海洋近亲中。这些家族的基因在脊椎动物和节肢动物的头部模式中起着重要的作用。具体目标有两个。一个是详细研究Coots基因在水螅头部图案中的作用，以及研究它在细胞周期穿越中的作用，初步证据表明它具有这种作用。这些努力将通过多种方法进行，包括在组织操作和功能研究期间检查表达模式的改变。二是分离和鉴定水螅头发育过程中其他基因的作用。重点将放在上述家庭的基因。

Bode 9723660 During the last 10-15 years a great deal has been learned about the genes and processes that regulate the development of an embryo into a functioning animal. One of the most interesting aspects of the accumulating knowledge is that a common set of regulatory genes involved in a common, or related, set of mechanisms underlie many of the developmental processes of the metazoans studied so far. These common features raise interesting and important questions as to how early during evolution did these genes arise? Were they already present in the Ur-metazoan? What developmental mechanisms and developmental processes did they participate in? And, to what extent were the mechanisms and processes invented early and conserved through animal evolution? One approach to these issues is to study these genes and their functions in organisms that belong to groups of animals that arose very early during metazoan evolution, such as the cnidaria, whose members include jellyfish, sea anemones, and the freshwater hydra. Of these, hydra, is particularly useful since the developmental processes (pattern formation, control of the proliferation and differentiation of the several cell types) are well-understood. Further, a number of genes known to regulate developmental events in many vertebrates and invertebrates have also been isolated, and in part, characterized in hydra. The overall aim of the proposed work is to determine if the genes and mechanisms underlying the development of the head of hydra are similar to those found in the development of the heads of vertebrates and insects. One such gene has already been found. Cnotx a hydra homologue, of the members of the Otx family has been characterized and shown to be involved in the development of the tentacles, a particular structure of the hydra head. There is also evidence that homologues of the Dlx and Emx families exist in hydra, or a close marine relative. Genes of these families play important roles in the patterning of the head in vertebrates and arthropods. The detailed aims are two. One is to examine in the role of the Coots gene in patterning of the hydra head in detail as well as to investigate its role in cell cycle traverse, a role that preliminary evidence suggests it has. These efforts will be pursued with a variety of approaches including examining alterations of expression patterns during tissue manipulations and functional studies. The other is to isolate and characterize the role of other genes involved in head development in hydra. The focus will be on genes of the families mentioned above.