Gradient Morphogens and Body Patterning Mechanisms

在果蝇黑腹果蝇（Drosophila melanogaster, Dm）中，母体转录因子Bicoid （Bcd）沿早期胚胎的前后轴沿长距离核梯度分布。Bcd功能的突变导致头部和其他前部结构的完全丧失，并在胚胎两端形成尾巴状结构。在分子水平上，Bcd是通过两个主要途径指定前发育的主要调节因子。首先，Bcd阻止了尾蛋白的翻译，尾蛋白是一种与后部发育有关的蛋白质。其次，Bcd激活了20多个目标基因的转录，每个目标基因都负责形成前结构的部分网络。尽管Bcd在Dm中很重要，但在大多数昆虫中没有发现Bcd。然而，最近的研究表明，另一种转录因子Orthodentical （Otd）可能在至少另外两种与Dm有远亲关系的昆虫中发挥主前调节作用。这是令人惊讶的，因为Bcd蛋白和Otd蛋白之间的氨基酸序列几乎没有相似性。在初步实验中，采用基因工程的方法用相似的od梯度代替Dm中母体Bcd梯度。令人惊讶的是，母系提供的Otd挽救了缺乏Dm Bcd的突变体中缺失的大部分前部结构。因此，这项研究的目的是了解为什么如此不同结构的蛋白质在胚胎发育中可以提供相似的功能。这些实验将准确地确定哪些特定的Bcd依赖活动可以由Otd提供，然后测试Bcd和Otd蛋白的哪些部分是开启参与前模式的靶基因所必需的。这些实验结果将引起发育生物学、分子进化和计算生物学等领域的研究人员的极大兴趣，并将从科学的角度产生更广泛的影响。就更广泛的教育影响而言，该项目还将为本科生和研究生提供良好的培训机会，并加强目前吸引和培训代表性不足的少数民族学生的努力。

Stephen J. SmallProposal IOS-0744966Gradient morphogens and body patterning mechanisms In the fruit fly Drosophila melanogaster (Dm), the maternal transcription factor Bicoid (Bcd) is distributed in a long range nuclear gradient along the anterior posterior (AP) axis of the early embryo. Mutations in Bcd function cause the complete loss of the head and other anterior structures, and the formation of tail-like structures at both ends of the embryo. At the molecular level, Bcd is a master regulator that specifies anterior development via two major pathways. First, Bcd prevents the translation of Caudal, a protein involved posterior development. Second, Bcd activates transcription of more than twenty target genes, each of which is responsible for part of the network that makes anterior structures. Despite its importance in Dm, Bcd is not found in most insects. However, recent studies suggest that another transcription factor, Orthodentical (Otd), may play the role of master anterior regulator in at least two other insects, which are distantly related to Dm. This is surprising because there is very little amino acid sequence similarity between the Bcd and Otd proteins. In preliminary experiments, a genetic engineering approach was used to replace the maternal Bcd gradient in Dm with a similar gradient of Otd. Surprisingly, maternally provided Otd rescued most of the anterior structures missing in mutants lacking Dm Bcd. Thus, the goal of this research is to understand why proteins of such different structures can provide similar functions in embryonic development. The experiments will define exactly which specific Bcd-dependent activities can be provided by Otd, and then test which parts of the Bcd and Otd proteins are required for turning on the target genes involved in anterior patterning. The results of these experiments will be of great interest to researchers in the fields of developmental biology, molecular evolution, and computational biology, and will have Broader Impacts from a scientific perspective. In terms of educational Broader Impacts, the project will also provide excellent training opportunities for students at the undergraduate and graduate levels, and augment current efforts to attract and train under-represented minority students.