SGER: Characterization of the Magnetic Compass in C57 BL/6 Mice

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Characterization of the Magnetic Compass is C57 BL/6 MiceJohn B. PhillipsBiology DepartmentVirginia TechBlacksburg, VA 24061-0406Project Summary. The proposed research will use a behavioral approach with laboratory mice to investigate the sensory mechanism responsible for detection of the Earth's magnetic field. The C57 BL/6 strain of laboratory mouse will be used to investigate whether a newly-discovered class of photopigments involved in synchronizing circadian rhythms to the light-dark cycle (cryptochromes), which have also been implicated in magnetic field sensing, are an essential component of the mouse's magnetic compass. Experiments will also be carried out to determine whether low-level, broad band (1-20 MHz) radio frequency fields disrupt magnetic compass orientation (as shown in recent studies of birds and amphibians). For a given frequency (7 MHz) shown to affect magnetic compass orientation of birds, the intensity threshold for an effect on magnetic compass orientation in the mouse system will be determined. The potential impact of this work includes: (1) characterization of the mechanism responsible for magnetic field sensitivity in a small mammal; (2) characterization of the molecular changes that have occurred during the evolution of a novel sensory system (the magnetic compass) from a well-characterized antecedent (the light-dependent circadian clock); (3) development of 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; (4) development of collaborative research programs with a number of laboratories in the USA and abroad with the goals of: a) using discrete radio frequencies to characterize the biophysical processes underlying the magnetic compass, b) modeling the changes in a light-sensitive circadian clock that would be necessary to optimize sensitivity to small, magnetic-field-dependent modulations of light input, and c) identifying brain regions involved in the processing of magnetic information.