Investigating the multiple roles of cryptochromes in animal magnetoreception

Many species, including humans, are reported to be magnetosensitive. Indeed, some animals navigate using the weak magnetic field (MF) of Earth. Others do not, but there are accounts of MF-effects and the concern that exposure to low frequency MFs may affect health. Whether the same or different mechanisms may be involved, is currently unknown. One mechanism has acquired experimental prominence. Cryptochromes (CRYs), best known for their role in circadian rhythmicity, may mediate magnetosensitivity via a photochemical quantum reaction involving CRY-bound flavin adenine dinucleotide (FAD) and a chain of tryptophan residues within CRY that generate a radical pair (RP). Unexpectedly, we have demonstrated that the CRY C-terminal (CRY-CT), without the canonical FAD binding site or tryptophan chain, elicits behavioural and cellular responses to MFs in Drosophila melanogaster. Our results do not necessarily contradict the RP model but urge a fundamental revision of its canonical interpretation. We propose a multidisciplinary programme of work examining each level of the sensory chain, including detection, signal transduction and amplification, cellular and behavioural responses. Our combined expertise includes quantum physics, computational chemistry, protein biophysics, electrophysiology, molecular genetics, and behaviour. We are thus uniquely positioned to address and move towards solving this fascinating and fundamental biological question.