Characterizing the Mechanism of Magnetoreception in C57BL/6 Mice

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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.