New research led by University of Leicester and University of Manchester scientists shows that a molecule present in all living cells called flavin adenine dinucleotide can, at high enough amounts, impart magnetic sensitivity on a biological system.
Drosophila melanogaster and other non-migrating animals can sense external magnetic fields. Image credit: University of Manchester.
The ability of species to navigate considerable distances has long intrigued the biological community.
One of several environmental cues to support these migrations is the geomagnetic field.
Moreover, several other behaviors respond reliably to magnetic fields, at least under laboratory conditions, showing that the ability to sense and react to magnetic fields is not limited to migrating animals.
However, the identity of the primary magnetoreceptors, the mechanisms that underlies their reported light dependence and how the magnetic signal is transduced remain unclear.
“How we sense the external world, from vision, hearing through to touch taste and smell, are well understood,” said Professor Richard Baines, a neuroscientist at the University of Manchester.
“But by contrast, which animals can sense and how they respond to a magnetic field remains unknown.”
“This study has made significant advances in understanding how animals sense and respond to external magnetic fields — a very active and disputed field.”
To do so, Professor Baines and colleagues exploited the fruit fly (Drosophila melanogaster) to manipulate gene expression to test out their ideas.
The fruit fly, although very different on the outside, contains a nervous system that works exactly the same way as ours and has been used in countless studies as a model to understand human biology.
“And that is because a magnetic field carries very little energy, unlike photons of light or sound waves used by the other senses which, by comparison, pack a big punch,” said Dr. Adam Bradlaugh, also from the University of Manchester.
To get around this, nature has exploited quantum physics and cryptochrome, a light-sensitive protein found in animals and plants.
“The absorption of light by cryptochrome results in movement of an electron within the protein which, due to quantum physics, can generate an active form of cryptochrome that occupies one of two states,” said Dr. Alex Jones, a quantum chemist at UK’s National Physical Laboratory.
“The presence of a magnetic field impacts the relative populations of the two states, which in turn influences the active-lifetime of this protein.”
“One of our most striking findings, and one that is at odds with current understanding, is that cells continue to ‘sense’ magnetic fields when only a very small fragment of cryptochrome is present,” Dr. Bradlaugh said.
“That shows cells can, at least in a laboratory, sense magnetic fields through other ways.”
“We identify a possible ‘other way’ by showing that a basic molecule, present in all cells can, at high enough amounts, impart magnetic sensitivity without any part of cryptochromes being present.”
“This molecule, flavin adenine dinucleotide (FAD) is the light sensor that normally binds to cryptochromes to support magnetosensitivity.”
The findings are important because understanding the molecular machinery that allows a cell to sense a magnetic field provides us with better ability to appreciate how environmental factors may impact on animals that rely on a magnetic sense to survive.
The magnetic field effects on FAD in the absence of cryptochrome also provide a clue as to the evolutionary origins of magnetoreception, in that it seems likely that cryptochrome has evolved to utilize magnetic field effects on this ubiquitous and biologically ancient metabolite.
“This study may ultimately allow us to better appreciate the effects that magnetic field exposure might potentially have on humans,” said University of Leicester’s Professor Ezio Rosato.
“Moreover, because FAD and other components of these molecular machines are found in many cells, this new understanding may open new avenues of research into using magnetic fields to manipulate the activation of target genes.”
“That is considered a holy-grail as an experimental tool and possibly eventually for clinical use.”
The study was published in the journal Nature.
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A.A. Bradlaugh et al. Essential elements of radical pair magnetosensitivity in Drosophila. Nature, published online February 22, 2023; doi: 10.1038/s41586-023-05735-z
