FORMATION OF THE DROSOPHILA SALIVARY GLAND

摘要 果蝇唾液腺（SG）是揭示其分子和细胞事件的理想模型 上皮管状器官的形成和生理特化，如肺、肾和 人类的分泌腺。SG是一个简单的管状器官，使用相同的形态发生 作为更复杂的高等动物器官的变化，包括细胞形状的变化， 运动SG也是胚胎中最大的分泌器官，为细胞如何分泌提供了理想的模型。 实现高水平的分泌能力，以及能力的变化如何与表达协调， 分泌物我们已经发现了四个关键的转录因子，在转录过程中起主要作用。 SG的形态发生和生理特化，我们已经确定了许多/大多数它们的 使用全基因组方法的转录靶点。在这个提议中，我们探索这些蛋白质如何 既可独立发挥作用，也可作为较大复合物的一部分，调节上皮管的不同方面 发展在具体目标#1中，我们使用全基因组体内DNA结合测定来测试我们的模型， SG特异性基因产物的表达水平是通过三个关键的配位结合介导的， 转录因子- Fkh，果蝇FoxA的直系同源物，Sage，一种不太高度保守的bHLH蛋白 仅在SG中表达，和Sens，其SG表达需要Fkh的锌指转录因子，和 圣人我们问CrebA，一种增加分泌能力的bZip转录因子，是否也能提高SG水平 直接或间接靶向基因表达。我们将鉴定每种蛋白质的结合位点，无论是在WT SG中还是 在SGs突变体中每种转录因子。特定顺式作用位点的生物学相关性将是 在已知靶基因的代表性子集中验证。这些研究将揭示我们是否已经确定了 控制SG基因表达的主要因素，并测试增强子组织的机制模型， 在一个系统中，关键的主要参与者及其下游目标是已知的， 被操纵了在具体目标#2和#3中，我们重点关注Sage、Sens和CrebA独立功能， Fkh在控制上皮管形成中的作用。我们已经确定了Fkh靶基因，当突变破坏 管形态发生的早期阶段。我们想知道这些早期Fkh靶基因的产物如何与 膜和细胞骨架蛋白，以协调细胞形状和排列的变化， 内化我们进一步使用来自目标#1的Fkh结合数据来鉴定另外的关键形态发生学。 监管部门

ABSTRACT The Drosophila salivary gland (SG) is an ideal model for revealing the molecular and cellular events underlying formation and physiological specialization of epithelial tubular organs, such as the lungs, kidneys, and secretory glands of humans. The SG is a simple tubular organ that forms using the same morphogenetic changes as more complicated organs of higher animals, including changes in cell shape, adhesion and movement. The SG is also the largest secretory organ in the embryo providing an ideal model for how cells achieve high-level secretory capacity and how changes in capacity are coordinated with the expression of secretory content. We have discovered four key transcription factors that play major roles in the morphogenesis and physiological specialization of the SG, and we have identified many/most of their transcriptional targets using genome-wide approaches. In this proposal, we explore how these proteins function both independently and as part of larger complexes to regulate distinct aspects of epithelial tube development. In Specific aim #1, we use genome-wide in vivo DNA binding assays to test our model that the levels of expression of SG specific gene products is mediated through the coordinate binding of three key transcription factors – Fkh, the Drosophila FoxA orthologue, Sage, a less highly conserved bHLH protein expressed in only the SG, and Sens, a zinc-finger transcription factor whose SG expression requires Fkh and Sage. We ask if CrebA, a bZip transcription factor that increases secretory capacity, also boosts levels of SG target gene expression directly or indirectly. We will identify binding sites for each protein, both in WT SGs and in SGs mutant for each other transcription factor. The biological relevance of specific cis acting sites will be validated in a representative subset of known target genes. These studies will reveal if we have identified the major factors controlling SG gene expression, and tests mechanistic models of enhancer organization and function in a system where the key major players and their downstream targets are known and can be manipulated. In Specific aims #2 and #3, we focus on the Sage, Sens and CrebA – independent functions of Fkh in controlling formation of epithelial tubes. We have identified Fkh target genes that when mutant disrupt early stages of tube morphogenesis. We ask how the products of these early Fkh target genes interface with membrane and cytoskeletal proteins to coordinate changes in cell shape and arrangement during tube internalization. We further use the Fkh binding data from aim #1 to identify additional key morphogenetic regulators.