CELLULAR COMMUNICATION IN MORPHOGENESIS

在黑腹果蝇和其他昆虫中，氧气被供应给 组织由气管系统，一个网络的分支上皮管 它在气门处向外开放， 身体大量细小的终末分支到达组织， 将空气直接输送到使用地点。终端分支是 由位于主动脉末端的气管细胞以一种有趣的方式形成， 气管分支：每个终端细胞发出许多长，分支 细胞质的延伸，随后“挖空”，形成几十个 细小管末端分支的形成是由来自 缺氧组织，新的分支生长出来，覆盖了 组织.然而，人们对这些信号的化学性质知之甚少 或者它们如何被转化为对末端分支生长的影响。 这项工作的长期目标是确定气管源性 信号，以确定组织如何调节信号产生 氧气需要，以了解信号是如何被接收和转换的， 终末气管细胞，并阐明亚细胞机制 驱动细胞质生长和分支形成。我们已经确定 三个基因，修剪/DSRF，修剪，误导，这是特别的， 在这个过程中需要。其中之一，修剪/DSRF，是同源的 哺乳动物血清，反应，转录因子，作为 一种生长因子调节的转录复合物。修剪/DSRF是 在终末细胞中特异性表达， 末端分枝;在修剪/DSRF突变体中，存在末端细胞 但它们不能形成细胞质延伸和细胞质的末端分支， 气管树明显缺席。提出了修剪/DSRF 蛋白质是终末细胞中受调节的转录复合物的一部分 由需要氧气的动物分泌的气管信号激活 靶组织。该项目的具体目标是： 1.分析组成性激活形式的修剪/DSRF对 在终末细胞中表达，以检验假设， 修剪/DSRF是末端分支的关键调节步骤。 2.确定修剪/DSRF是否在Ras/Map激酶信号传导中起作用 与SRF一样，通过表达激活和显性负性形式 Ras/MAPK信号转导元件在终末细胞中的表达。 3.克隆和分子特征修剪和误导，两个基因 终端分支形成和路径查找所需的，并确定 他们在这些过程中的作用和他们的职能关系， 修剪/DSRF。 4.进行额外的基因筛选，以确定其他基因， 是终端分支的形成和生长所必需的，以确定 突变体中的细胞缺陷，并在功能上排列新基因 关于修剪/DSRF和其他参与基因的基因， 过程

In a Drosophila melanogaster and other insects, oxygen is supplied to the tissues by the tracheal system, a network of branched epithelial tubes that opens to the outside at the spiracles and extends branches throughout the body. Extensive arrays of fine terminal branches reach the tissues and transport air directly to the sites of utilization. Terminal branches are formed in an intriguing way by tracheal cells located at the ends of major tracheal branches: each terminal cell sends out many long, branches cytoplasmic extensions that subsequently "hollow out" forming dozens of fine tubules. Formation of terminal branches is induces by signals from oxygen-starved tissues, and the new branches grow out and cover the tissue. Little is known though about the chemical nature of the signals or how they are transduced into an effect on terminal branch outgrowth. The long term objectives of this work are to identify the tracheogenic signal(s), to determine how signal production is regulated by tissue oxygen need, to understand how the signal is received and transduced by the terminal tracheal cells, and to elucidate the subcellular mechanisms that drive cytoplasmic outgrowth and branch formation. We have identified three genes, pruned/DSRF, trimmed, and misguided, that are specifically required in this process. One of these, pruned/DSRF, is the homologue of mammalian serum, response, transcription factor which functions as part of a growth factor regulated transcription complex. pruned/DSRF is specifically expressed in the terminal cells throughout the period of terminal branching; in pruned/DSRF mutants, the terminal cells are present but they fail to form cytoplasmic extensions and the terminal branches of the tracheal tree are strikingly absent. It is proposed that pruned/DSRF protein is part of a regulated transcription complex in terminal cells that is activated by a tracheogenic signal secreted by oxygen-requiring target tissues. The specific aims of this project are: 1. To analyze the effects of constitutively activated forms of pruned/DSRF expressed in terminal cells, in order to test the hypothesis that pruned/DSRF is part of key regulated step in terminal branching. 2. To determine if pruned/DSRF functions in a Ras/Map kinase signalling cascade as does SRF, by expressing activated and dominant negative forms of Ras/MAPK signalling components in the terminal cells. 3. To clone and molecularly characterize trimmed and misguided, two genes required for terminal branch formation and path finding, and to determine their roles in these processes and their functional relationships to pruned/DSRF. 4. To carry out additional genetic screens to identify other genes that are required for terminal branch formation and outgrowth, to determine the cellular defects in the mutants, and to functionally order the new genes with respect to pruned/DSRF and other genes that are involved in the process.