Understanding Mechanisms Underlying Drosophila Neurofibromatosis-1 Defects

描述（由申请人提供）：1 型神经纤维瘤病 (NF1) 是一种高度可变且不可预测的疾病，其严重程度似乎由迄今未知的修饰基因决定。 NF1 基因编码神经纤维蛋白，其唯一公认的功能是充当 Ras 的负调节因子。除了良性和恶性肿瘤之外，NF1 患者还患有一些不太为人所知的非肿瘤症状，包括整体生长缺陷和学习问题。果蝇 NF1 模型显示出与这些非肿瘤症状相似的表型。引人注目的是，大多数果蝇 NF1 表型不容易通过减弱 Ras 信号传导而改变，但可以通过增加 cAMP 依赖性蛋白激酶 A (PKA) 途径的信号传导来恢复。这使得确定 NF1 如何影响 cAMP 信号成为 NF1 研究的中心问题。我们的结果表明，果蝇 NF1 突变体的整体生长缺陷反映了特定幼虫神经元对 RasGAP 活性的非细胞自主需求。我们最初认为这种主要的 Ras 信号传导缺陷反过来会导致继发性激素缺陷，通过增加 cAMP 可以缓解这种缺陷。现在的新证据提出了另一种双功能假说，该假说指出，NF1 不仅是神经内分泌细胞调节 Ras 和一种或多种激素产生所必需的，而且也是激素反应细胞中有效地将激素受体与腺苷酸环化酶偶联的必需品。我们提出了结合遗传和生化方法来测试这一假设的优点，这可能解释了为什么我们和其他人对表型拯救所必需的 NF1 功能得出了相互矛盾的结论。我们的新结果表明神经内分泌 Ret 酪氨酸激酶和腺苷酸环化酶偶联神经肽受体及其配体是 NF1 大小缺陷的遗传抑制因子。我们提出了四套相互关联的遗传和生化实验来跟进这些结果，并实现我们的总体目标，即提供 NF1 缺陷背后机制的分子描述。公共卫生相关性 1 型神经纤维瘤病 (NF1) 是人类最常见的遗传性疾病之一。据估计，NF1 的发病率为 3,000 分之一，表明仅在美国就可能有 100,000 名 NF1 患者。在这个项目中，我们将在遗传模型生物（黑腹果蝇）中结合使用生化、分子生物学和遗传方法，以确定导致 NF1 缺陷的机制。更好地了解这些机制是合理治疗 NF1 的必要步骤。

DESCRIPTION (provided by applicant): Neurofibromatosis type 1 (NF1) is a highly variable and unpredictable disease, the severity of which appears to be determined by as yet unknown modifier genes. The NF1 gene encodes neurofibromin, whose only agreed upon function is to serve as a negative regulator of Ras. Beyond benign and malignant tumors, NF1 patients also suffer from several less well understood non-tumor symptoms, including an overall growth deficiency and learning problems. A Drosophila NF1 model displays phenotypes resembling these non-tumor symptoms. Strikingly, most Drosophila NF1 phenotypes are not readily modified by attenuating Ras signaling, but are restored by increasing signaling through the cAMP-dependent protein kinase A (PKA) pathway. This has made determining how NF1 affects cAMP signaling a central issue in NF1 research. Our results indicate that the overall growth defect of Drosophila NF1 mutants reflects a non-cell-autonomous requirement for RasGAP activity in specific larval neurons. We initially suggested that this primary Ras signaling defect in turn causes a secondary hormonal defect, which is mitigated by increasing cAMP. New evidence now suggests an alternative dual-function hypothesis, which states that NF1 is not just required in neuroendocrine cells to regulate Ras and the production of one or more hormones, but also in hormone responding cells to efficiently couple hormone receptors to adenylyl cyclase. We propose a combination of genetic and biochemical approaches to test the merits of this hypothesis, which may explain why we and others have reached contradictory conclusions about NF1 functions essential for phenotypic rescue. Our new results have implicated the neuroendocrine Ret tyrosine kinase, and an adenylyl cyclase-coupled neuropeptide receptor and its ligand as genetic suppressors of the NF1 size defect. We propose four interconnected sets of genetic and biochemical experiments to follow up on these results, and to achieve our overall goal of providing a molecular description of mechanisms underlying NF1 defects. PUBLIC HEALTH RELEVANCE Neurofibromatosis type 1 (NF1) is among the most common genetic diseases of man. Its estimated incidence of 1 in 3,000 suggests there may be 100,000 NF1 patients in the US alone. In this project we will use a combination of biochemical, molecular biological, and genetic approaches in the genetic model organism, Drosophila melanogaster, to identify mechanisms responsible for NF1 defects A better understanding of these mechanisms is a required step on the road to rational therapy for NF1.