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一致引起，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，但药物毒性的个体间差异也是一种复杂疾病。不幸的是，在确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。在药物基因组学领域尤其如此，在该领域很难招募到大量同质的受影响患者，而且毒性的潜在病因可能是异质的。在本研究中，我们探索了在果蝇中鉴定具有介导药物毒性的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。与通过传统的诱变筛选（例如x射线或EMS）鉴定的基因相比，在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基因。我们将首先研究的药物是甲氨蝶呤，因为它在临床上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目标通路的保存。实验很简单，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系中阐明甲氨蝶呤和其他药物毒性的遗传结构，每组系最初来源于8个高度近交的始祖系。这些RI线为我们识别和定位QTL提供了很大的能力，也为我们估计任何已映射的QTL的种群频率提供了极其重要的能力。我们将从每条RI线中抽取雌性果蝇，并将其暴露于甲氨蝶呤和选定的其他药物的浓度中，使成年雌性果蝇暴露于该药物三天后，生育力明显下降。我们将确定基因型相互作用的毒性是由中频或罕见的致病因素引起的。由于用于衍生约1500个RI系的每一个创始者自交系都已被完全测序，因此了解已绘制的QTL的“相位”将允许鉴定定义已绘制的QTL的实际核苷酸位点。

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.