Genetic analysis of circadian responses to low frequency electromagnetic fields in Drosophila melanogaster.
Genetic analysis of circadian responses to low frequency electromagnetic fields in Drosophila melanogaster.
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DOI：
10.1371/journal.pgen.1004804
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发表时间：
2014-12
期刊：
影响因子：
4.5
通讯作者：
Kyriacou CP
中科院分区：
文献类型：
--
作者：
Fedele G;Edwards MD;Bhutani S;Hares JM;Murbach M;Green EW;Dissel S;Hastings MH;Rosato E;Kyriacou CP
蓝光敏感的光感受器隐色素（CRY）可能通过形成涉及色氨酸三元组的自由基对而充当磁感受器。先前对果蝇对电磁场的行为反应进行的遗传学分析使用了条件、昼夜节律和地理趋顺性分析，为自由基对模型（RPM）提供了一些支持。在这里，我们描述了一种新的方法，可以对电磁场产生一致和可靠的昼夜节律反应，这种反应与已经报道的大不相同。我们使用Schuderer仪器将果蝇从局部环境变量中分离出来，观察极低频（3至50 Hz）场诱导的两种运动表型、昼夜节律和活动水平的变化。这些场诱导的表型依赖于CRY和蓝光，并与增强的CRY稳定性相关。对三聚体的末端色氨酸的突变分析表明，该残基对于RPM所需的电子转移是必不可少的，而该残基对于场响应不是必需的。我们观察到，CRY c端的缺失显著减弱了emf诱导的周期变化，而n端的缺失则导致了过度活跃。最引人注目的是，一个不编码色氨酸三联体和FAD结合结构域的分离的CRY c端能够介导适度的emf诱导的周期变化。最后，我们观察到hCRY2而不是hCRY1的变形子可以检测电磁场，这表明hCRY2是蓝光响应的。相比之下，当我们在蓝光下检测野生型小鼠视交叉上核切片的昼夜节律分子周期时，没有场效应。因此，我们的结果与经典的Trp三联体介导的RPM不一致，并表明CRYs作为蓝光/EMF传感器取决于特定细胞环境中存在的交互作用因素。低频电磁场（emf）与电力线有关，并与儿童白血病的发展有关。然而，地球也有一种天然的电磁场，动物可以探测到，并利用它来导航和定位自己，特别是在迁徙期间。其中一种方法是使用一种叫做隐色素的特殊光感受器，当它被光激活时，会在分子内产生易受电磁场影响的变化。隐色素是动物生物钟的重要组成部分，24小时的计时器决定了每天的行为和生理周期。我们研究了果蝇的昼夜节律行为，并观察到电磁场对隐花色素介导的果蝇睡眠-觉醒周期的一些新颖而强大的影响。通过使用隐花色素突变体，我们发现我们的结果不支持这种分子如何对电磁场作出反应的经典模型。我们还表明，哺乳动物隐色素在转基因果蝇体内可以对EMF产生反应，而在哺乳动物生物钟神经元中则不能。因此，隐花色素的EMF响应性是由其细胞内环境决定的，这表明与隐花色素相互作用的其他未知分子也非常重要。
The blue-light sensitive photoreceptor cryptochrome (CRY) may act as a magneto-receptor through formation of radical pairs involving a triad of tryptophans. Previous genetic analyses of behavioral responses of Drosophila to electromagnetic fields using conditioning, circadian and geotaxis assays have lent some support to the radical pair model (RPM). Here, we describe a new method that generates consistent and reliable circadian responses to electromagnetic fields that differ substantially from those already reported. We used the Schuderer apparatus to isolate Drosophila from local environmental variables, and observe extremely low frequency (3 to 50 Hz) field-induced changes in two locomotor phenotypes, circadian period and activity levels. These field-induced phenotypes are CRY- and blue-light dependent, and are correlated with enhanced CRY stability. Mutational analysis of the terminal tryptophan of the triad hypothesised to be indispensable to the electron transfer required by the RPM reveals that this residue is not necessary for field responses. We observe that deletion of the CRY C-terminus dramatically attenuates the EMF-induced period changes, whereas the N-terminus underlies the hyperactivity. Most strikingly, an isolated CRY C-terminus that does not encode the Tryptophan triad nor the FAD binding domain is nevertheless able to mediate a modest EMF-induced period change. Finally, we observe that hCRY2, but not hCRY1, transformants can detect EMFs, suggesting that hCRY2 is blue light-responsive. In contrast, when we examined circadian molecular cycles in wild-type mouse suprachiasmatic nuclei slices under blue light, there was no field effect. Our results are therefore not consistent with the classical Trp triad-mediated RPM and suggest that CRYs act as blue-light/EMF sensors depending on trans-acting factors that are present in particular cellular environments. Low frequency electromagnetic fields (EMFs) are associated with electrical power lines and have been implicated in the development of childhood leukemias. However, the Earth also has a natural EMF that animals can detect and which they use in order to navigate and orient themselves, particularly during migrations. One way they might do this is by using specialised photoreceptors called cryptochromes, which when activated by light, generate changes within the molecule that are susceptible to EMFs. Cryptochromes are important components of animal circadian clocks, the 24 hour timers that determine daily behavioral and physiological cycles. We have studied the circadian behavior of the fruitfly and have observed some novel and robust effects of EMFs on the fly's sleep-wake cycle that are mediated by cryptochrome. By using cryptochrome mutants we find that our results do not support the classic model for how this molecule might respond to EMFs. We also show that mammalian cryptochromes can respond to EMF when placed into transgenic Drosophila, whereas in mammalian clock neurons, they cannot. Consequently, the EMF responsiveness of cryptochrome is determined by its intracellular environment, suggesting that other, unknown molecules that interact with cryptochrome are also very important.
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影响因子：
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