A new animal model to elucidate mechanisms of gene regulation and embryonic patterning

项目摘要 HOX基因是发育过程的重要调节因子。在此期间它们的功能受到干扰 胚胎发生导致戏剧性的“同源异型”表型，在这种表型中，身体的各个区域从一个 对另一个人的身份。在人类中，这些干扰可能导致面部、耳朵、四肢和 生殖器，以及神经缺陷和癌症。在许多动物基因组中，HOX基因以簇的形式存在： 在脊椎动物中，这些簇是紧凑的，而无脊椎动物的簇则排列得更松散或 支离破碎。虽然仍然知之甚少，但假设HOX星系团的结构在 管理他们的部署。然而，这在脊椎动物身上很难研究，因为它们的基因组编码多个 HOX簇是全基因组复制的结果。而无脊椎动物通常有一个单一的 作为HOX基因的补充，许多无脊椎动物的HOX簇被破坏，包括在经典的 苍蝇和线虫等无脊椎动物模型系统。 为了解决这一不足，我们开发了研究头足类软体动物(鱿鱼和乌贼)的资源和工具 章鱼)，包括染色体规模的基因组组装、广泛的转录切分和基因工具 操纵。通过这项工作，我们发现头足类有一个单一的，完整的，但大量的 扩展的Hox群集。事实上，它们编码了迄今描述的最大的Hox星团--Squid Hox星团是 比在人类身上发现的大两个数量级。头足类中HOX簇的保守性 尤其令人惊讶的是，它们的基因组在其他方面相对于其他动物是高度重排的。值得注意的是， 我们发现头足类Hox基因表现出规范的、共线的嵌套结构域的表达， 这表明，尽管发生了戏剧性的变化，但头足类动物仍保留了祖先调节程序的要素 增加群集大小。令人惊讶的是，我们的初步基因敲除数据表明，HOX基因的丢失会导致 身体区域的缺失，而不是转化。这些结果-首次对HOX进行了功能分析 软体动物中的基因指向与同源异型转化完全不同的作用模式 以苍蝇和人类等明显被分割的动物为特征。了解两者之间的差异 巨大的头足类Hox集群和脊椎动物中发现的更紧凑的排列将提供 在不同动物中对这些身体计划转录因子调控的基本见解 物种，包括人类。因此，这个项目准备提供对生物学的变革性洞察 HOX基因，它在人类发育和疾病中发挥关键作用，并对我们的基础 在胚胎发育中如何建立模式的知识。

Project Summary Hox genes serve as critical regulators of developmental processes. Disruption of their function during embryogenesis results in dramatic “homeotic” phenotypes where regions of the body are transformed from one identity to another. In humans, these disruptions can lead to malformation of the face, ears, limbs, and genitalia, as well as neural defects and cancer. In many animal genomes, the Hox genes are found in clusters: in vertebrates, these clusters are compact, while those of invertebrates are more loosely arranged or fragmented. While still poorly understood, the structure of the Hox cluster is hypothesized to be important in regulating their deployment. However, this is difficult to study in vertebrates as their genomes encode multiple Hox clusters that are the result of whole genome duplications. While invertebrates typically have a single complement of Hox genes, many invertebrate Hox clusters are disrupted, including those found in the classic invertebrate model systems like flies and nematodes. To address this deficit, we have developed resources and tools for studying cephalopod molluscs (squid and octopus), including chromosome-scale genome assemblies, extensive transcriptomics, and tools for gene manipulation. Through this work, we have found that cephalopods have a single, intact, but massively expanded Hox cluster. In fact, they encode the largest Hox clusters yet described – the squid Hox cluster is two orders of magnitude larger than those found in humans. Conservation of the Hox cluster in cephalopods is particularly striking given that their genomes are otherwise highly rearranged relative to other animals. Notably, we have found that cephalopod Hox genes exhibit the canonical, collinear nested domains of expression, suggesting that elements of the ancestral regulatory program are retained in cephalopods despite the dramatic increase in cluster size. Surprisingly, our preliminary knockout data suggest that loss of a Hox gene results in the absence, rather than the transformation, of body regions. These results - the first functional analysis of Hox genes in a mollusc - point to a fundamentally different mode of action than the homeotic transformations characteristic of overtly segmented animals like flies and humans. Understanding differences between the massive cephalopod Hox clusters and the more compact arrangement found in vertebrates will provide fundamental insights concerning the regulation of these body plan transcription factors across diverse animal species, including humans. This project is therefore poised to provide transformational insights into the biology of Hox genes, which play key roles in human development and disease, and contribute to our fundamental knowledge of how pattern is established in embryogenesis.