CELLULAR COMMUNICATION IN MORPHOGENESIS

在果蝇和其他昆虫中，氧气供应给 气管系统的组织，一个由分支上皮管组成的网络 在气孔处向外开放，并将分支延伸至全身 身体。广泛排列的细小末端分支到达组织和 将空气直接输送到使用地点。终端分支机构有 由位于主干末端的气管细胞以一种耐人寻味的方式形成 气管分支：每个末端细胞发出许多长长的分支 细胞质延伸，随后“掏空”形成数十个 细小的小管。末端分支的形成是由以下信号诱导的 缺氧的组织，新的枝条长出来覆盖着 组织。然而，人们对这些信号的化学性质知之甚少 或者它们如何转化为对末端分枝生长的影响。 这项工作的长期目标是确定气管来源的 信号(S)，以确定组织如何调节信号产生 氧气需求，以了解信号是如何接收和传递的 气管末端细胞，并阐明亚细胞机制 驱动细胞质生长和分枝形成的物质。我们已经确定了 三个基因，剪枝/DSRF，剪裁，和误导，是特定的 在此过程中需要。其中之一，pruned/dsrf，是 哺乳动物血清、反应、转录因子，其功能是 一个生长因子调节的转录复合体。已修剪/DSRF为 在整个时期中在末端细胞中特异表达 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终末分枝 令人惊讶的是，气管树不见了。建议修剪/DSRF 蛋白质是末端细胞中受调控的转录复合体的一部分。 它是由需氧分泌的气管信号激活的 目标组织。该项目的具体目标是： 1.分析构成激活形式的剪枝/DSRF的影响 在末端细胞中表达，以检验假设 修剪/DSRF是末端分枝中关键调控步骤的一部分。 2.确定修剪/DSRF是否在RAS/MAPK信令中起作用 与SRF一样，通过表达激活的和显性的否定形式而级联 终端小区中的RAS/MAPK信令组件。 3.克隆剪裁和误导两个基因并进行分子特征分析 终端分支形成和路径查找所需的，并确定 它们在这些过程中的作用以及它们与 已修剪/DSRF。 4.进行额外的基因筛查，以确定其他 是末端分枝形成和延伸所必需的，以确定 突变体中的细胞缺陷，并对新基因进行功能排序 关于剪枝/DSRF和其他参与 进程。

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.