Formation of the Drosophila salivary gland

果蝇唾液腺(SG)是揭示分子和细胞的理想模型 上皮性管状器官形成和生理特化的基础事件，如 人的肺、肾和分泌腺。SG是一个简单的管状器官，它形成 使用与高等动物更复杂的器官相同的形态发生变化，包括 细胞形态、黏附和运动的变化。SG也是人类最大的分泌器官 胚胎为细胞如何获得高水平的分泌能力以及如何 能力的变化与分泌内容的表达相协调。我们有 发现了四个关键的转录因子，它们在形态发生和 SG的生理特化，我们已经鉴定了他们的许多/大部分转录 使用全基因组方法的靶标。在这个提案中，我们探索这些蛋白质是如何发挥作用的 既独立又作为较大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 SG特异性基因产物的表达水平通过 三个关键转录因子-Fkh，果蝇FoxA同源基因， SAGE是一种不太保守的bHLH蛋白，仅在SG和Sens中表达 其SG表达需要Fkh和Sage的转录因子。我们问克雷巴是不是bZip 增加分泌能力的转录因子，也提高了SG靶基因的水平 直接或间接表达。我们将确定每种蛋白质的结合位点，这两种结合位点都在WT SGS中 并在SGS中相互突变为转录因子。特定顺式基因的生物学相关性 作用位点将在一个具有代表性的已知目标基因子集中得到验证。这些研究将 揭示我们是否确定了控制SG基因表达的主要因素，并进行了测试 增强者组织和功能的机制模型在一个系统中 玩家和他们的下游目标是已知的，可以被操纵。在具体目标2中 和#3，我们重点讨论了Fkh在控制中的Sage、Sens和Creba无关的功能 上皮管的形成。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的产物是如何针对基因的 与膜和细胞骨架蛋白的接口，以协调细胞形状和 管子内化过程中的排列。我们进一步使用来自目标#1的FKH绑定数据 确定其他关键的形态发生调控因子。

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.