Formation of the Drosophila salivary gland

果蝇唾液腺（SG）是揭示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，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 细胞形状、粘附和运动的变化。 SG也是最大的分泌器官 胚胎为细胞如何实现高水平分泌能力以及如何 能力的变化与分泌内容的表达相协调。我们有 发现了四个在形态发生中起重要作用的关键转录因子 SG 的生理特化，我们已经确定了它们的许多/大部分转录 使用全基因组方法的目标。在本提案中，我们探索这些蛋白质如何发挥作用 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 模型表明 SG 特异性基因产物的表达水平是通过 三个关键转录因子的协调结合——Fkh，果蝇 FoxA 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（一种锌指） 其SG表达需要Fkh和Sage的转录因子。我们询问 CrebA 是否为 bZip 增加分泌能力的转录因子，也提高 SG 靶基因的水平 直接或间接表达。我们将在 WT SG 中识别每种蛋白质的结合位点 以及在 SGs 突变体中每个转录因子。特定顺式的生物学相关性 作用位点将在已知靶基因的代表性子集中进行验证。这些研究将 揭示我们是否已确定控制 SG 基因表达的主要因素，并进行测试 系统中增强子组织和功能的机械模型，其中关键专业 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 #3，我们重点关注 Sage、Sens 和 CrebA——Fkh 在控制方面的独立功能 上皮管的形成。我们已经确定了 Fkh 靶基因，当突变体破坏时 管形态发生的早期阶段。我们问这些早期Fkh靶基因的产物如何 与膜和细胞骨架蛋白相互作用以协调细胞形状的变化 管内化过程中的排列。我们进一步使用目标 #1 中的 Fkh 绑定数据来 确定其他关键的形态发生调节因子。

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.