Drosophila as a model for chemotherapy pharmacogenomics

描述（由申请人提供）：复杂的疾病，由几个潜在的上位基因与环境协同作用引起，导致大部分人类疾病。复杂疾病的例子包括冠状动脉疾病和II型糖尿病，但药物毒性的个体间差异也是一种复杂疾病。不幸的是，在鉴定导致复杂疾病的遗传位点（数量性状位点或QTL）方面进展缓慢。这在药物基因组学领域尤其如此，在该领域难以招募大量同质的受影响患者，并且毒性的潜在病因可能是异质的。在这个建议中，我们探索的效用，确定基因窝藏常设遗传变异介导的药物毒性在果蝇，出口新发现的基因到人类的目标。与通过传统诱变筛选鉴定的基因相比，果蝇中导致药物毒性持续变异的基因可能是导致人类个体间变异的基因的更好候选者（例如，X射线或EMS）。我们将研究的第一种药物是甲氨蝶呤，因为它广泛用于治疗癌症和关节炎，已知毒性，以及从人类到果蝇的靶向通路的保护。这些实验很简单，我们将把我们的工作扩展到另外三种对人类有毒性的药物。我们将阐明甲氨蝶呤和其他药物毒性的遗传结构，在两组约750果蝇RI线，每个最初来自8个高度近交的创始人线的集合。这些RI系为我们鉴定和定位QTL提供了很大的力量，也为我们估计任何定位QTL的群体频率提供了极其重要的能力。我们将从每个RI系中抽取雌蝇，并将其暴露于甲氨蝶呤和其他选定药物的浓度，使成年雌蝇暴露于药物3天后生育力显著降低。我们将确定基因型相互作用的毒性是否是由于中间频率或罕见的频率致病因素。由于用于衍生~1500 RI系的每个创始近交系都将被完全测序，因此定位QTL的“相位”的知识将允许鉴定定义定位QTL的实际核苷酸位点。 公共卫生相关性：甲氨蝶呤被广泛用作化疗药物和治疗关节炎中的关节肿胀，但在许多情况下，由于毒副作用而暂停使用。由于果蝇和人类共享甲氨蝶呤靶向的遗传途径，研究将确定果蝇中调节毒性的DNA多态性。未来的工作可以询问这些相同的基因是否调节人类的毒性，可能导致基因测试，以确定最有可能从甲氨蝶呤治疗中受益的患者。预期其他化疗药物的结局相似。

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.