Niemann Pick C disease in Drosophila

描述（由申请人提供）：尼曼-皮克C型（NPC）是一种遗传性儿童神经退行性疾病，被认为是由于神经元中未酯化胆固醇的积累。在模式生物果蝇中，有两个NPCI基因，NPC1a和NPC1b。然而，在这些基因中没有已知的点突变，因此，它们在疾病或发育中的作用尚不清楚。NPC1蛋白与发育调节因子和肿瘤抑制因子形态原补丁（Ptc）具有显著的同源性。推动这一提议的第一个假设是ptc突变文件产生了一种类似npc的疾病。这是基于我们的以下发现：(1)我们分离了ptc的一个成年特异性等位基因，这些果蝇表现出进行性的、年龄依赖性的运动缺陷；(2)这些突变体的大脑显示出与NPC神经元和其他溶酶体储存疾病中发现的包涵体相似的神经元。推动这一提议的第二个假设是，ptc果蝇中鼻窦炎疾病状态的主要原因不是神经元中胆固醇的积累。这是基于我们的发现，超载的胆固醇途径在野生型导致胆固醇的积累和神经元包涵体的形成；然而，这些果蝇不会出现任何行为缺陷。同样，给变异果蝇喂食胆固醇也不会使疾病恶化。这与先前的观察一致，即包裹体的存在程度与疾病的严重程度之间没有相关性。推动这一提议的第三个假设是果蝇的NPC1蛋白可能与Ptc一起调节发育过程。这是基于我们的观察，ptc突变体中的一些发育缺陷是部分渗透的，两个NPC1基因是果蝇中最接近ptc的基因，可能弥补了ptc活性的丧失。因此，我们的具体目标是：1)确定ptc突变果蝇发生NPC样疾病的原因：分子基础；2)分离dNPC1突变并确定：a)这些基因的功能丧失是否导致NPC疾病；b)这两个基因是否为神经发生所必需；c) ptc和NPC1在疾病和发育中的关系；3)进行修饰筛选以分离dNPC1基因的成人特异性突变。这项工作将提供深入了解这些蛋白质在神经退行性疾病和发展中的作用。

DESCRIPTION (provided by applicant): Niemann-Pick type C (NPC) is an inherited, pediatric neurodegenerative disease thought to be due to the accumulation of unesterified cholesterol in neurons. In the model organism Drosophila, there are two NPCI genes, NPC1a and NPC1b. However, there are no known point mutations in these genes, and consequently, their role in disease or development is not known. The NPC1 proteins have significant homology to the developmental regulator and tumor suppressor morphogen Patched (Ptc).The first hypothesis driving this proposal is that ptc mutant files develop a NPC-like disease. This is based on our following findings: (1) we have isolated an adult specific allele of ptc and these flies show progressive, age-dependent locomotor deficits, (2) the brains from these mutants show neurons with inclusion bodies similar to the inclusions found in neurons of NPC and several other lysosomal storage disorders. The second hypothesis driving this proposal is that the primary cause for the NPC disease-state in ptc flies is not the accumulation of cholesterol in neurons. This is based on our finding that overloading the cholesterol pathway in wild type leads to accumulation of cholesterol and formation of inclusion bodies in neurons; however, these flies do not develop any of the behavioral defects. Similarly, feeding cholesterol to mutant flies does not worsen the disease-state. These are consistent with the previous observation that there is no correlation between the extent of presence of inclusions and the severity of the disease. The third hypothesis driving this proposal is that the NPC1 proteins in Drosophila might regulate developmental processes in conjunction with Ptc. This is based on our observation that some of the developmental defects in ptc mutants are partially penetrant and that the two NPC1 genes are the closest of ptc in flies and might complement the loss of Ptc activity.Thus, our specific aims are: 1) Determine why ptc mutant flies develop the NPC-like disease: the molecular basis, 2) Isolate dNPC1 mutations and determine: a) if loss of function for these genes leads to the NPC disease, b) if the two genes are required for neurogenesis, and c) the relationship between Ptc and NPC1 in disease and development, 3) Perform modifier screens to isolate adult specific mutations in dNPC1 genes. This work will provide insight into the role of these proteins in neurodegenerative diseases and development.