The Structure, Evolution, and Deployment of the Hox Cluster in a Basal Cnidarian

9727224马丁代尔霍克斯星团的结构、进化和部署现代动物展示了一系列令人眼花缭乱的形式，或称“身体计划”。传统的生物学方法，如古生物学和比较胚胎学，到目前为止已经被证明无法解释导致新的身体计划的进化转变。幸运的是，分子生物学已经揭示了连续性的潜在证据。例如，像老鼠和果蝇这样分化的动物被发现在发育过程中使用一组共同的基因来建立它们的前后轴。这些被称为HOX基因的基因很重要，因为它们代表着一种保守的发育特征，在进化过程中，动物的身体规划发生了变化。只有认识到这种保守的特征，我们才有希望确定负责新身体计划的新机制的进化。我们已经从海葵身上恢复了HOX基因，这是一种简单的海洋动物，其身体结构与老鼠和苍蝇都有根本的不同。显然，HOX基因非常古老，一定是在5亿多年前这些高度分化的生物进化分裂之前进化出来的。有趣的是，海葵没有前后轴。这种不一致提出了两个重要的问题：(1)HOX基因在缺乏前后轴的动物(如海葵)中的今天的作用是什么？以及(2)关于HOX基因的祖先作用，这揭示了什么？我们的研究试图确定HOX基因在海葵中的作用，方法是检查这些基因的染色体组织，并确定这些基因在发育中的生物体中何时何地被“开启”。通过这样做，我们希望深入了解这些基因在进化过程中的作用，以及它们对动物身体计划进化的意义。

9727224 Martindale The Structure, Evolution, and Deployment of the Hox Cluster in a Basal Cnidarian Modern day animals exhibit a bewildering array of forms, or "body Plans." Classical biological approaches, such as paleontology and comparative embryology, have so far proved unable to elucidate the evolutionary transitions responsible for new body plans. Fortunately, molecular biology has revealed underlying evidence of continuity. For example, animals as divergent as mice and fruitflies have been found to use a common set of genes to establish their anterior-posterior axis during development. These genes, known as Hox genes, are important because they represent a conserved feature of development that is shared by animals whose body plans have diverged during evolution. Only by recognizing such conserved features can we hope to identify the evolution of novel mechanisms responsible for new body plans. We have recovered Hox genes from a sea anemone, a simple marine animal whose body plan is radically different from both mice and flies. Evidently, the Hox genes are very ancient and must have evolved prior to the evolutionary split between these highly divergent organisms, over 500 million years ago. Interestingly, sea anemones do not possess an anterior-posterior axis. This inconsistency raises two important questions: (1) What is the present-day role of Hox genes in animals such as sea anemones that lack an anterior-posterior axis? And (2) What does this reveal about the ancestral role of the Hox genes? Our research seeks to establish the role of Hox genes in the sea anemone by examining the chromosomal organization of these genes, and by determining where and when these genes are "turned-on" in the developing organism. In doing so, we expect to gain insight into the role of these genes during evolution and their significance for the evolution of animal body plans.