Gradient Morphogens and Body Patterning Mechanisms

SmallProposal IOS-0744966在果蝇黑腹果蝇(DM)中，母体转录因子BCD沿早期胚胎的前、后(AP)轴分布在长距离的核梯度上。BCD功能的突变会导致头部和其他前部结构的完全丧失，并在胚胎的两端形成类似尾巴的结构。在分子水平上，BCD是一个主要的调节因子，通过两条主要途径指定前部发育。首先，BCD阻止了Caudal的翻译，Caudal是一种涉及后天发育的蛋白质。其次，BCD激活了20多个目标基因的转录，每个基因都负责构成前部结构的网络的一部分。尽管BCD在DM中很重要，但大多数昆虫中都没有BCD。然而，最近的研究表明，另一种转录因子Orthodentical(OTD)可能在至少两种与DM有远缘关系的昆虫中扮演着主要的前调节因子的角色。这是令人惊讶的，因为BCD和OTD蛋白之间的氨基酸序列相似性很小。在初步实验中，一种基因工程方法被用来用类似的OTD梯度来取代DM的母体BCD梯度。令人惊讶的是，母体提供的OTD挽救了缺乏DM BCD的突变体中缺失的大部分前结构。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。这些实验将准确地定义OTD可以提供哪些特定的BCD依赖活动，然后测试BCD和OTD蛋白的哪些部分是启动涉及前部模式的目标基因所必需的。这些实验的结果将引起发育生物学、分子进化和计算生物学领域的研究人员的极大兴趣，并将从科学角度产生更广泛的影响。在更广泛的教育影响方面，该项目还将为本科生和研究生提供极好的培训机会，并加强目前吸引和培训代表性不足的少数族裔学生的努力。

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.