Characterizing the Mechanism of Magnetoreception in C57BL/6 Mice

项目摘要。对C57BL/6小鼠进行的磁‘COMPASS’定向的行为学分析正被用来研究负责感知地磁场的分子和生物物理机制。有两种潜在的神经机制已被证明足够敏感，足以让陆地动物检测到地球强度(50微特斯拉)的磁场：涉及铁磁性磁铁矿颗粒的机制(“磁铁矿机制”)和涉及形成自由基对中间体的光诱导生化反应的机制(“自由基对机制”)。实验室小鼠C57BL/6品系的基因敲除正被用于研究隐色素是否是小鼠磁罗盘的重要组成部分。隐色素被认为在基于自由基对机制的磁罗盘中发挥核心作用。小鼠的实验还被用来检验：(1)自由基对机制假说的关键预测，即磁罗经定向应受到低水平、宽带(1-10 MHz)射频场的干扰，以及(2)磁铁机制的关键预测，即磁罗经定向应通过事先暴露于短暂的高强度磁脉冲而被扰乱。最后，小鼠试验被用来确定射频干扰对磁罗盘反应影响的阈值。这项工作的潜在影响包括：(1)在模型哺乳动物系统中表征负责磁场敏感性的生物物理机制；(2)展示哺乳动物系统对一种新型物理刺激(即~1-10 MHz范围内的射频场)的敏感性；(3)表征磁罗盘的分子组件；以及(4)开发生物物理和遗传学技术来操纵对磁信息的获取，这些信息可用于研究磁刺激在其他行为和神经生理反应(如啮齿动物空间记忆的行为和神经方面)中的作用。这项工作的更广泛影响包括本科生、研究生和博士后研究员在神经行为学/感觉生物学和认知心理学的界面上接受独特的跨学科培训。

Project Summary. A behavioral assay of magnetic 'compass' orientation in C57 BL/6 mice is being used to investigate the molecular and biophysical mechanisms responsible for sensing the geomagnetic field. Two potential neural mechanisms have been shown to be sensitive enough for terrestrial animals to detect earth-strength (50 micro Tesla) magnetic fields: mechanisms involving particles of a ferromagnetic magnetite ("magnetite mechanisms") and mechanisms involving photoinduced biochemical reactions that form radical pair intermediates ("radical pair mechanism"). Genetic knockouts of the C57BL/6 strain of laboratory mouse are being used to investigate whether cryptochromes, proposed to play a central role in a radical pair mechanism-based magnetic compass, are an essential component of the mouse's magnetic compass. The mouse assay is also being used to test: (1) a critical prediction of the radical pair mechanism hypothesis, which is that magnetic compass orientation should be disrupted by low-level, broad band (1-10 MHz) radio frequency fields, and (2) a critical prediction of the magnetite mechanism, which is that magnetic compass orientation should be disrupted by prior exposure to a brief, high intensity magnetic pulse. Finally, the mouse assay is being used to determine the threshold for effects of radio frequency interference on the magnetic compass response. The potential impact of this work includes: (1) characterizing the biophysical mechanism responsible for magnetic field sensitivity in a model mammalian system; (2) demonstrating sensitivity of a mammalian system to a new class of physical stimuli (i.e., radio frequency fields in the ~1-10 MHz range); (3) characterizing molecular components of the magnetic compass; and (4) developing biophysical and genetic techniques for manipulating access to magnetic information that can be used to investigate the role of magnetic stimuli in other behavioral and neurophysiological responses (e.g., behavioral and neural aspects of spatial memory in rodents). Broader impacts of this work include exposure of undergraduate students, graduate students and post-doctoral fellows to unique interdisciplinary training at the interface of neuroethology/sensory biology and cognitive psychology.