PNAS惊人发现：感知气温的基因

夏日的午后总是让人昏昏欲睡，这是为什么呢?Leicester大学的科学家们发现了一个感知气温的基因，向人们展示了环境温度和天气状况对基因活性的影响。这项研究发表在六月二十八日的美国国家科学院院PNAS杂志上。

为了适应地球自转引起的昼夜周期性变化，我们进化出了生物钟协调不同组织与器官的昼夜节律。人体内部的生物钟，对于人类行为和生理机能有着重要的影响，一直是相关领域的研究热点。当然生物钟并不是人类的专利，地球上绝大多数植物、动物、真菌和蓝藻都具有生物钟。黑腹果蝇具有24小时的生物钟，是研究人类昼夜节律的重要模式生物。

Leicester大学的研究人员观察了环境气温对黑腹果蝇生物钟的具体影响。跟许多人一样，实验室里的黑腹果蝇也会在午后小憩一下。不过研究人员发现这种现象只存在于实验室的人工环境下，果蝇在野外的行为是截然相反的，它们在午后更加活跃。

研究显示，果蝇午后的高度活跃受到TrpA1基因的控制。这个基因就像是一个温度感应器，介导了环境诱导的行为改变。

“我们知道TrpA1基因在果蝇生物钟所在的大脑区域中表达。不过，在这些细胞中去除TrpA1并没有影响果蝇的午后活动，” Bambos Kyriacou大学的Bambos Kyriacou教授说。“当我们在其他神经元中去除TrpA1表达时，果蝇的午后活动才收到干扰。我们在此基础上定位了一个细胞亚群。”

对于包括人类在内的陆生生物来说，24小时昼夜节律几乎渗透到了行为和生理的方方面面。如果生物钟与正常的明暗环境不协调(比如经常需要上夜班的人)，就会引起大量的健康问题，比如肥胖症、心血管功能障碍甚至一些癌症。

“我们的研究还表明，与实验室环境相比，在天然环境中研究动物可以更好的理解基因对动物行为的控制。只在实验室的人工环境下做实验，可能会得出错误的结论。也就是说，建立了数十年的成熟生物钟理论，可能需要作出重大的修正，”Kyriacou教授补充道。

原文标题：：Drosophila circADIan rhythms in seminatural environments: Summer afternoon component is not an artifact and requires TrpA1 channels

Under standard laboratory conditions of rectangular light/dark cycles and constant warm temperature,Drosophila melanogaster show bursts of morning (M) and evening (E) locomotor activity and a “siesta” in the middle of the day. These M and E components have been critical for developing the neuronal dual oscillator model in which clock gene expression in key cells generates the circadian phenotype. However, under natural European summer conditions of cycling temperature and light intensity, an additional prominent afternoon (A) component that replaces the siesta is observed. This component has been described as an “artifact” of the TriKinetics locomotor monitoring system that is used by many circadian laboratories world wide. Using video recordings, we show that the A component is not an artifact, neither in the glass tubes used in TriKinetics monitors nor in open-field arenas. By studying various mutants in the visual and peripheral and internal thermo-sensitive pathways, we reveal that the M component is predominantly dependent on visual input, whereas the A component requires the internal thermo-sensitive channel transient receptor potential A1 (TrpA1). Knockdown of TrpA1 in different neuronal groups reveals that the reported expression of TrpA1 in clock neurons is unlikely to be involved in generating the summer locomotor profile, suggesting that other TrpA1 neurons are responsible for the A component. Studies of circadian rhythms under seminatural conditions therefore provide additional insights into the molecular basis of circadian entrainment that would otherwise be lost under the usual standard laboratory protocols.

作者：秩名