Formation of the Drosophila salivary gland

描述（由申请人提供）：在发育过程中，器官前体通过局部转录因子和信号事件的组合被指定。细胞生长、重排和定向迁移在器官发育过程中塑造和定位器官。最终，不同器官内的细胞获得了独特的生理适应，使它们能够执行特定的功能。许多在特定器官发育过程中起作用的分子通路也需要在成人结构中维持功能。不能实现和维持特殊功能往往导致器官衰竭和退化，因此与几种人类疾病和先天缺陷有关。为了了解器官是如何形成并获得其独特的生理适应性，我们使用了一个简单的模型：果蝇的唾液腺，这是动物中最大的分泌器官。它由两个配对的分泌管和较小的导管组成，前者合成和分泌大量的蛋白质，后者连接分泌管和口腔，充当唾液腺分泌物的管道。在之前的工作中，我们和其他人已经确定了局部转录因子和信号通路，这些转录因子和信号通路决定了唾液腺形成的位置，控制了唾液腺募集的细胞数量，并区分了该器官中的主要细胞类型。我们还确定了六种早期表达的转录因子，它们对唾液腺形态和生理有深远的影响。在这项应用中，我们建议(1)确定在早期唾液腺中表达的六个转录因子基因的下游靶点，这些基因是腺体形态发生和生理的关键；(2)确定细胞形状变化和细胞重排对试管形成的相对贡献；(3)确定周围组织如何有助于最终正确放置唾液腺。在目的1中，我们将使用全载原位杂交来确定193多个已知的唾液腺基因中哪一个是由六个转录因子基因中的每一个调节的。在目标2中，我们将使用标记细胞的实时成像来确定在试管内翻和伸长期间通常发生多少细胞重排，并且我们将描述介导细胞形状变化和重排的基因转录靶点的关键子集。在目标3中，我们将描述唾液腺导航到正确最终位置所需的信号通路。

DESCRIPTION (provided by applicant): During development, organ precursors are specified through a combination of localized transcription factors and signaling events. Cell growth, rearrangement and directed migration shape and position organs as they develop. Ultimately, cells within different organs acquire unique physiological adaptations that allow them to perform their specialized functions. Many of the molecular pathways that function during the development of specific organs are also required to maintain function in the adult structures. Failure to achieve and maintain specialized functions often leads to organ failure and degeneration, and is thus linked to several human diseases and birth defects. To learn how organs form and acquire their unique physiological adaptations, we are using a simple model: the Drosophila salivary gland, which is the largest secretory organ in the animal. It is comprised of two paired secretory tubes, which synthesize and secrete large amounts of proteins, and smaller duct tubes, which connect the secretory tubes to the mouth and serve as a conduit for the salivary gland secretions. In previous work, we and others have identified the localized transcription factors and signaling pathways that determine where the salivary gland will form, that control the number of cells recruited to a salivary gland fate and that distinguish among the major cell types in this organ. We have also identified six early expressed transcription factors that have profound effects on salivary gland morphology and physiology. In this application, we propose to (1) identify the downstream targets of the six transcription factor genes that are expressed in the early salivary gland and are key to gland morphogenesis and physiology; (2) to determine the relative contributions of cell shape change and cell rearrangement to tube formation; and (3) determine how surrounding tissues contribute to the final correct placement of the salivary gland. In aim 1, we will use whole mount in situ hybridization to determine which of 193+ known salivary gland genes are regulated by each of the six transcription factor genes. In aim 2, we will use live imaging of marked cells to determine how much cell rearrangement normally occurs during tube invagination and elongation, and we will characterize a key subset of the transcriptional targets of the genes that mediate cell shape change and rearrangement. In aim 3, we will characterize signaling pathways necessary for the salivary gland to navigate to its correct final position.