NITRIC OXIDE AND RESPONSES TO HYPOXIA IN DROSOPHILA

氧对许多生命形式都是必不可少的。氧气供应不足（缺氧）可能是有害的。局部缺氧造成的损害，如中风，会影响人体健康。细胞和整个生物体对缺氧的适应发生在从细菌到人类的物种中。我们建议研究缺氧反应的机制在一个模型实验生物，果蝇。在初步工作中，我们已经表明，缺氧诱导幼虫的探索行为，并阻止细胞周期。这些反应也可以由一氧化氮（NO）诱导，并被NO抑制剂抑制。因此，一氧化氮，一种已知的哺乳动物信号分子，可以通过促进血管舒张来增加血液流向缺氧组织，也在果蝇对缺氧的反应中发挥作用。我们提出了遗传和分子方法来剖析反应途径并探索NO的作用。我们会筛选那些无法在缺氧中存活的突变体。由于这种反应促进了生存，缺氧敏感突变体将包括对缺氧反应的突变体。表型分析将用于对突变进行分类，并且将详细检查影响感兴趣过程的突变类。我们将重点关注那些在感知氧气方面有缺陷的突变，或者那些在细胞周期或对缺氧的行为反应中发生改变的突变。利用转基因、药物和突变的分子研究将探索阻止细胞周期进展的机制。将开发类似的工具来剖析信号转导途径，该途径在响应缺氧时引发行为和细胞周期进程的适应性变化。

Oxygen is essential to many forms of life. Shortfalls in oxygen supply (hypoxia) can be deleterious. Damage resulting from local hypoxia, as occurs in stroke, influences human health. Cellular and whole-organism adaptations to hypoxia occur in species from bacteria to humans. We propose to study the mechanisms of the responses to hypoxia in a model experimental organism, Drosophila. In preliminary work, we have shown that hypoxia induces an exploratory behavior in larvae, and arrests the cell cycle. These responses can also be induced by nitric oxide (NO) and suppressed by NO inhibitors. Hence, NO, a known mammalian signaling molecule that can increase blood flow to hypoxic tissues by promoting vasodilation, has a role in responding to hypoxia in flies too. We propose genetic and molecular approaches to dissect the response pathway and to explore the role of NO. We will screen for mutants that fail to survive hypoxia. Since the response promotes survival, hypoxia sensitive mutants will include mutants in the response to hypoxia. Phenotypic analysis will be used to classify mutants, and mutant classes affecting processes of interest will be examined in detail. We will focus on mutations that are defective in sensing oxygen or those that are altered in cell cycle or behavioral responses to hypoxia. Molecular studies using transgenes, drugs and mutations will probe the mechanisms that arrest cell cycle progression. Similar tools will be developed to dissect the signal transduction pathway that provokes adaptive changes in behavior and cell cycle progression in response to reduced oxygen.