Formation of the Drosophila salivary gland

果蝇唾液腺（SG）是研究果蝇唾液腺分子和细胞功能的理想模型 上皮管状器官形成和生理特化的基础事件，例如 人类的肺、肾和分泌腺。SG是一个简单的管状器官， 使用与高等动物更复杂器官相同的形态发生变化，包括 细胞形状、粘附和运动的变化。SG也是最大的分泌器官， 胚胎提供了一个理想的模型，细胞如何实现高水平的分泌能力， 容量的变化与分泌内容物的表达相协调。我们有 发现了在形态发生中起主要作用的四个关键转录因子， SG的生理专业化，我们已经确定了许多/大部分他们的转录 使用全基因组方法的目标。在这个建议中，我们探索这些蛋白质如何发挥作用， 既独立地又作为较大复合物的一部分来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 SG特异性基因产物的表达水平是通过 三个关键转录因子- Fkh，果蝇FoxA直向同源物， Sage是一种仅在SG中表达的不太保守的bHLH蛋白，Sens是一种锌指蛋白， SG表达需要Fkh和Sage的转录因子。我们问CrebA，一个bZip 增加分泌能力的转录因子，也能提高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， 和SGs突变体中的每一个其他转录因子。特定顺式异构体的生物学相关性 将在已知靶基因的代表性子集中验证作用位点。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 增强子组织和功能的机制模型，其中关键的主要 参与者及其下游目标是已知的并且可以被操纵。具体目标#2 和#3，我们专注于Sage，Sens和CrebA -Fkh在控制中的独立功能 上皮管的形成。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 与膜和细胞骨架蛋白的界面，以协调细胞形状的变化， 管内化期间的布置。我们进一步使用来自目标#1的Fkh结合数据， 确定其他关键形态发生调节因子。

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.