Genetic Analysis of Circadian Responses to Low Frequency Electromagnetic Fields in Drosophila melanogaster

Giorgio Fedele, Mathew Edwards, Supriya Bhutani, John Hares, Manuel Murbach, Edward Green, Stephane Dissel, Michael Hastings, Ezio Rosato, and Charalambos Kyriacou, PLoS Genetics, Volume 10, Issue 12, online December 4, 2014

Animals can detect the Earth’s static magnetic field and use it for navigation and geo-orientation. Magnetoreception may be mediated by the blue-light sensitive photoreceptor cryptochrome (CRY) by means of a radical pair mechanism (RPM) involving photoactivation of the flavin adenine dinucleotide (FAD) cofactor and subsequent intramolecular electron transfer from nearby conserved tryptophan residues. CRYs are also important components of animal circadian clocks, the 24-hour biological timers that regulate daily behavioral and physiological cycles. Previously reported genetics findings of CRY-dependent behavioral responses of Drosophila melanogaster to electromagnetic fields based on conditioning, circadian, and geotaxis assays support the involvement of CRY in magnetoreception.

This study describes a novel method to generate uniquely consistent and reliable circadian responses to electromagnetic fields. The flies were exposed in a sXcELF system supplied by the IT’IS Foundation. The applied ELF-EMFs (3 – 50 Hz and 0.3 – 1 mT) induced changes in two locomotor phenotypes, circadian period, and activity levels. These field-induced phenotypes are CRY- and blue-light dependent and are correlated with enhanced CRY stability. Endogenous mammalian CRYs, however, were not found to be directly sensitive to light or EMF in a circadian assay in mouse suprachiasmatic nucleus slices. The results support that CRYs act as blue-light/EMF sensors in the circadian response, but that the response depends on as yet unidentified factors present in the cellular environment.

The scientific and technical impact of the study can be summarized as:

  • Further evidence of ELF-EMF effects in Drosophila melanogaster circadian responses
  • Evidence for a link between cryptochromes, EMF, and the circadian clock
  • Robust bio-effects of moderate-intensity ELF-EMFs
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