FORMATION OF THE DROSOPHILA SALIVARY GLAND

摘要 果蝇唾液腺(SG)是揭示分子和细胞事件的理想模型 上皮性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，它使用相同的形态发生 随着高等动物更复杂的器官的变化，包括细胞形状、黏附和 有动静。SG也是胚胎中最大的分泌器官，为细胞如何 获得高水平的分泌能力，以及能力的变化如何与表达 秘密内容。我们已经发现了四个关键的转录因子，它们在 的形态发生和生理特化，我们已经鉴定了它们的许多/大部分 使用全基因组方法的转录靶标。在这个提案中，我们探索了这些蛋白质是如何 既独立地发挥作用，也作为更大的复合体的一部分来调节上皮管的不同方面 发展。在特定的目标#1中，我们使用全基因组体内DNA结合分析来测试我们的模型 SG特异性基因产物的表达水平是通过三个关键点的配位结合来调节的 转录因子-Fkh，果蝇FoxA同源基因，Sage，一种不太保守的bHLH蛋白 仅在SG和Sens中表达，Sens是一种锌指转录因子，其SG表达需要Fkh和 鼠尾草。我们问Creba，一种bZip转录因子，可以增加分泌能力，是否也能提高SG的水平 直接或间接的靶基因表达。我们将确定每种蛋白质的结合位点，包括在WT SGS和 在SGS中相互突变为转录因子。特定顺式作用部位的生物学相关性将是 在已知目标基因的代表性子集中得到验证。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，并检验增强子组织和 在系统中发挥作用，在该系统中，主要参与者及其下游目标是已知的，并且可以 被操纵了。在具体目标#2和#3中，我们重点介绍了与Sage、Sens和Creba无关的功能 FKH在控制上皮管形成中的作用我们已经确定了FKH靶基因，当突变破坏时 管子形态发生的早期阶段。我们问这些早期FKH靶基因的产物是如何与 膜和细胞骨架蛋白在培养过程中协调细胞形状和排列的变化 内部化。我们进一步使用来自AIM#1的FKH绑定数据来识别额外的关键形态发生 监管者。

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.