Bushnell Philip J, Ward William O, Morozova Tatiana V, Oshiro Wendy M, Lin Mimi T, Judson Richard S, Hester Susan D, McKee John M, Higuchi Mark
National Health and Environmental Effects Research Laboratory, U.S. EPA, Research Triangle Park, North Carolina.
Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina.
Toxicol Sci. 2017 Mar 1;156(1):230-239. doi: 10.1093/toxsci/kfw243.
Interpretation and use of data from high-throughput assays for chemical toxicity require links between effects at molecular targets and adverse outcomes in whole animals. The well-characterized genome of Drosophila melanogaster provides a potential model system by which phenotypic responses to chemicals can be mapped to genes associated with those responses, which may in turn suggest adverse outcome pathways associated with those genes. To determine the utility of this approach, we used the Drosophila Genetics Reference Panel (DGRP), a collection of ∼200 homozygous lines of fruit flies whose genomes have been sequenced. We quantified toluene-induced suppression of motor activity in 123 lines of these flies during exposure to toluene, a volatile organic compound known to induce narcosis in mammals via its effects on neuronal ion channels. We then applied genome-wide association analyses on this effect of toluene using the DGRP web portal (http://dgrp2.gnets.ncsu.edu), which identified polymorphisms in candidate genes associated with the variation in response to toluene exposure. We tested ∼2 million variants and found 82 polymorphisms located in or near 66 candidate genes that were associated with phenotypic variation for sensitivity to toluene at P < 5 × 10-5, and human orthologs for 52 of these candidate Drosophila genes. None of these orthologs are known to be involved in canonical pathways for mammalian neuronal ion channels, including GABA, glutamate, dopamine, glycine, serotonin, and voltage sensitive calcium channels. Thus this analysis did not reveal a genetic signature consistent with processes previously shown to be involved in toluene-induced narcosis in mammals. The list of the human orthologs included Gene Ontology terms associated with signaling, nervous system development and embryonic morphogenesis; these orthologs may provide insight into potential new pathways that could mediate the narcotic effects of toluene.
对高通量化学毒性检测数据的解读和应用需要将分子靶点的效应与全动物的不良结局联系起来。黑腹果蝇特征明确的基因组提供了一个潜在的模型系统，通过该系统可以将对化学物质的表型反应映射到与这些反应相关的基因上，这反过来可能提示与这些基因相关的不良结局途径。为了确定这种方法的实用性，我们使用了果蝇遗传参考面板（DGRP），这是一组约200个纯合果蝇品系的集合，其基因组已被测序。我们在暴露于甲苯期间，对这些果蝇的123个品系中甲苯诱导的运动活性抑制进行了量化，甲苯是一种挥发性有机化合物，已知其通过对神经元离子通道的作用在哺乳动物中诱导麻醉。然后，我们使用DGRP网站门户（http://dgrp2.gnets.ncsu.edu）对甲苯的这种效应进行全基因组关联分析，该分析确定了与甲苯暴露反应变化相关的候选基因中的多态性。我们测试了约200万个变体，发现82个多态性位于66个候选基因中或其附近，这些基因与对甲苯敏感性的表型变异相关，P值<5×10-5，并且这些候选果蝇基因中有52个具有人类直系同源基因。这些直系同源基因中没有一个已知参与哺乳动物神经元离子通道的经典途径，包括γ-氨基丁酸、谷氨酸、多巴胺、甘氨酸、5-羟色胺和电压敏感钙通道。因此，该分析没有揭示与先前显示参与哺乳动物甲苯诱导麻醉过程一致的遗传特征。人类直系同源基因列表包括与信号传导、神经系统发育和胚胎形态发生相关的基因本体术语；这些直系同源基因可能为介导甲苯麻醉作用的潜在新途径提供见解。
