Characterizing the Mechanism of Magnetoreception in C57BL/6 Mice

项目摘要。C57 BL/6小鼠的磁“罗盘”方向行为测定正在用于研究负责感知地磁场的分子和生物物理机制。 两种潜在的神经机制已经被证明是足够敏感的陆生动物检测地球强度（50微特斯拉）的磁场：机制涉及铁磁性磁铁矿的颗粒（“磁铁矿机制”）和机制涉及光诱导的生化反应，形成自由基对中间体（“自由基对机制”）。 对实验室小鼠C57 BL/6品系的基因敲除正被用于研究隐花色素是否是小鼠磁罗盘的重要组成部分，隐花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。 小鼠试验还用于测试：（1）自由基对机制假设的关键预测，即磁罗盘方向应被低水平宽带（1-10 MHz）射频场破坏，以及（2）磁铁矿机制的关键预测，即磁罗盘方向应被事先暴露于短暂的高强度磁脉冲破坏。 最后，正在使用小鼠试验来确定无线电频率干扰对磁罗盘响应的影响的阈值。 这项工作的潜在影响包括：（1）表征模型哺乳动物系统中负责磁场敏感性的生物物理机制;（2）证明哺乳动物系统对一类新的物理刺激的敏感性（即，在~1-10 MHz范围内的射频场）;（3）表征磁罗盘的分子成分;以及（4）开发用于操纵对磁信息的访问的生物物理学和遗传学技术，所述磁信息可用于研究磁刺激在其他行为和神经生理学响应中的作用（例如，啮齿动物空间记忆的行为和神经方面）。 这项工作的更广泛的影响包括本科生，研究生和博士后研究员接触独特的跨学科培训在神经行为学/感觉生物学和认知心理学的接口。

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.