Evolution of segmentation in chordates: dissecting the genetic mechanism of somitogenesis in the basal chordate, amphioxus

脊索动物分节的进化：剖析基底脊索动物文昌鱼体节发生的遗传机制

基本信息

批准号：
1952567
负责人：
Linda Holland
金额：
$ 77.5万
依托单位：
University of California-San Diego Scripps Inst of Oceanography
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-03-15 至 2025-02-28
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1952567&HistoricalAwards=false
关键词：
Evolution segmentation chordates dissecting genetic

项目摘要

Non-technical. Understanding how the thousands of genes that make up an organism’s genome (the genotype) interact to create the tissues and organs that together make up that organism (the phenotype) is one of the five ‘grand challenges of 21st century biology’ identified by the National Research Council. Dissecting this genotype-phenotype relationship is of great practical importance and is the focus of enormous research efforts. Importantly, it is key to understanding how organisms evolve and has wide-ranging implications for the health sciences, agriculture, biotechnology, and ecology. To address the genotype-phenotype relationship, this research uses amphioxus, a simple fish-like animal whose ancestors separated from the evolutionary line leading to vertebrates half a billion years ago. The specific question asked is how the amphioxus genome produces the segmented body muscles (similar to the repeating muscles along each side of a vertebrate such as a fish that allow side to side movement). Technical. The research will elucidate the gene network mediating muscle segmentation, and show at the single-cell level how this network controls the partitioning of cells into discrete segments (somites). Comparisons with vertebrates will show how this genetic mechanism has changed as vertebrates became larger and more complex. In amphioxus, muscle segments extend the full length of the body, but in vertebrates, there are none in the head. It is controversial whether vertebrates lost head segments or they are an amphioxus novelty. Much of the gene network for muscle segmentation appears to be conserved between amphioxus and vertebrates—in both, a “clock” specifies when segments will form, and Notch/Delta signaling mediates segmentation. However, in vertebrates, gradients of secreted proteins, chiefly Fgfs, specify where segment boundaries will form, but in amphioxus only the head segments, not those in the trunk or tail, require Fgfs. To test the theory that as vertebrates grew larger and lost head segments, the Fgf gradient was co-opted from the head to the posterior segments, key signaling pathways (Wnt/β-catenin; Fgf, Notch) in developing amphioxus will be perturbed with chemical inhibitors and activators at specific developmental times. Gene knockdown and overexpression will show gene hierarchy. Effects on morphology of segmentation will be reconstructed in 3-D by serial blockface scanning electron microscopy (SBSEM), which when done at intervals can show the steps in morphogenesis at the single cell level. Researchers will involve undergraduates and high school students directly in the project and also partner with the Birch Aquarium at Scripps Institution of Oceanography and the San Diego County Office of Education to lead workshops for high school teachers. These workshops will use locally-available marine invertebrates to show teachers how to instruct students in experimental design and data analysis—skills that are fundamental to training the next generation of scientists.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术性的。了解构成生物体基因组（基因型）的数千个基因如何相互作用以创建共同构成该生物体（表型）的组织和器官是“21 世纪生物学的五个重大挑战”之一。剖析这种基因型与表型的关系具有重要的实际意义，也是大量研究工作的重点，重要的是，它是了解生物体如何进化的关键，并且对健康科学、农业、生物技术，以及为了解决基因型与表型的关系，这项研究使用了文昌鱼，一种简单的类似鱼的动物，其祖先在五亿年前就与脊椎动物的进化谱系分离了，所提出的具体问题是文昌鱼基因组如何产生分段的身体。肌肉（类似于鱼类等脊椎动物两侧的重复肌肉，可以进行左右运动）。该研究将阐明介导肌肉分割的基因网络，并在单细胞中进行展示。与脊椎动物的比较将表明，随着脊椎动物变得更大和更复杂，这种网络如何控制细胞的划分，但在文昌鱼中，肌肉节段延伸到身体的整个长度。脊椎动物的头部没有这种结构，目前尚有争议的是，脊椎动物是否失去了头节，或者它们是文昌鱼的新奇物种，但肌肉分割的大部分基因网络似乎是保守的。在文昌鱼和脊椎动物中，“时钟”指定片段何时形成，Notch/Delta 信号介导分段。然而，在脊椎动物中，分泌蛋白（主要是 Fgfs）的梯度指定片段边界的形成位置，但在文昌鱼中只有片段边界。头部节段，而不是躯干或尾部的节段，需要 Fgfs。为了检验随着脊椎动物变大并失去头部节段的理论，Fgf 梯度为从头部到后段，文昌鱼发育过程中的关键信号通路（Wnt/β-连环蛋白；Fgf、Notch）将在特定的发育时期受到化学抑制剂和激活剂的干扰。基因敲低和过度表达将显示出基因层次结构。研究人员将通过连续块面扫描电子显微镜（SBSEM）以 3D 方式重建分割对形态发生的影响，每隔一段时间进行一次可以显示单细胞水平的形态发生步骤。让本科生和高中生直接参与该项目，并与斯克里普斯海洋学研究所的伯奇水族馆和圣地亚哥县教育办公室合作，为高中教师举办研讨会，这些研讨会将使用当地的海洋无脊椎动物向教师展示。如何指导学生进行实验设计和数据分析——这些技能是培养下一代科学家的基础技能。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查进行评估，被认为值得支持标准。