Drosophila as a model for chemotherapy pharmacogenomics

描述(申请人提供)：复杂的疾病，由几个潜在的上位性基因和环境共同引起，是人类疾病的主要原因。复杂疾病的例子包括冠状动脉疾病和II型糖尿病，但药物毒性的个体差异也是一种复杂疾病。不幸的是，在识别导致复杂疾病的遗传基因座(数量性状基因座或QTL)方面进展缓慢。这在药物基因组学领域尤其如此，在那里很难招募大量同质的受影响患者，而且潜在的毒性病因可能是不同的。在这项建议中，我们探索了识别含有调节果蝇药物毒性的长期遗传变异的基因的效用，目的是将新发现的基因输出到人类。与通过传统的突变筛选(例如X射线或EMS)鉴定的基因相比，导致果蝇药物毒性持续变异的基因可能是导致人类个体间变异的更好的候选基因。我们将首先检查的药物是甲氨蝶呤，因为它广泛用于治疗癌症和关节炎，已知的毒性，以及从人类到果蝇的靶向途径的保守。这些实验非常简单，我们将把我们的工作扩展到另外三种对人体有毒性的药物。我们将在两组约750个果蝇RI系中阐明甲氨蝶呤的遗传结构和其他药物毒性，每个系最初来自8个高度近交的创始人系。这些RI系给了我们很大的力量来识别和定位QTL，也给了我们极其重要的能力来估计任何定位的QTL的群体频率。我们将从每个RI品系中吸引雌性果蝇，并将它们暴露于甲氨蝶呤和其他选定药物的浓度中，使暴露于该药物三天的成年雌性果蝇表现出明显的生育能力下降。我们将确定由基因相互作用引起的毒性是由中频还是罕见的频率因素引起的。由于每个用于衍生~1500 RI系的方正自交系都将被完全测序，因此了解所定位的QTL的“相”将允许识别定义所定位的QTL的实际核苷酸位点。 公共卫生意义：甲氨蝶呤被广泛用作化疗药物和治疗关节炎的关节肿胀，但在许多情况下，由于毒副作用而被暂停使用。由于果蝇和人类共享甲氨蝶呤靶标的遗传途径，研究将确定果蝇中调节毒性的DNA多态。未来的工作可能会问，这些相同的基因是否会调节人类的毒性，可能会导致进行基因测试，以确定哪些患者最有可能从甲氨蝶呤治疗中受益。预计其他化疗药物也会出现类似的结果。

DESCRIPTION (provided by applicant): Complex diseases, caused by several potentially epistatic genes in concert with the environment, contribute to the bulk of human disease. Examples of complex diseases include coronary artery disease and Type II diabetes, but the inter-individual variation in drug toxicity is also a complex disease. Unfortunately, progress at identifying the genetic loci (Quantitative Trait Loci or QTL) contributing to complex disease has been slow. This is particularly true in the field of pharmacogenomics, where it is difficult to recruit large homogenous sets of affected patients and the underlying etiology of toxicity is likely to be heterogeneous. In this proposal we explore the utility of identifying genes harboring standing genetic variation that mediate drug toxicity in Drosophila, with the goal of exporting newly discovered genes to humans. Genes that contribute to standing variation in drug toxicity in Drosophila may be better candidates for genes contributing to inter-individual variation in humans than genes identified through traditional mutagenic screens (e.g., X-ray or EMS). The initial drug we will examine is Methotrexate because of wide clinical use to treat cancer and arthritis, known toxicities, and conservation of target pathways from humans to Drosophila. The experiments are simple enough that we will extend our work to three additional drugs that exhibit toxicity in humans. We will elucidate the genetic architecture of Methotrexate and other drug toxicity in a collection of two sets of ~750 Drosophila RI lines, each initially derived from eight highly inbred founder lines. These RI lines give us a great deal of power to both identify and localize QTL, and also gives us the extremely important ability to estimate the population frequency of any mapped QTL. We will draw female flies from each RI line and expose them to concentrations of Methotrexate and other drugs chosen so that adult female flies exposed to the drug for three days display a marked reduction in fertility. We will determine if toxicity by genotype interactions are due to intermediate frequency or rare in frequency causative factors. As each of the founder inbred lines used to derive the ~1500 RI lines will have been completely sequenced, knowledge of the "phase" of mapped QTL will allow the identification of the actual nucleotide sites that define mapped QTLs. PUBLIC HEALTH RELEVANCE: Methotrexate is widely used as both a chemotherapy agent and to treat joint swelling in arthritis, yet in many cases it use is suspended as a result of toxic side effects. As Drosophila and humans share the genetic pathway Methotrexate targets, research will identify DNA polymorphisms in Drosophila that modulate toxicity. Future work can then ask if these same genes modulate toxicity in humans, possibly leading to genetic tests to identify patients who could most likely benefit from Methotrexate treatment. Similar outcomes are expected for additional chemotherapy agents.