For migratory birds and sea turtles, the ability to sense the Earth’s magnetic field is crucial to navigating the long-distance voyages these animals undertake during migration. Humans, however, are widely assumed not to have an innate magnetic sense. Research published in Nature Communications by faculty at the University of Massachusetts Medical School shows that a protein expressed in the human retina can sense magnetic fields when implanted into Drosophila, reopening an area of sensory biology in humans for further exploration.
Sensing the earth’s magnetism isn’t that rare, according to Wikipedia: Magnetoception (or magnetoreception) is the ability to detect a magnetic field to perceive direction, altitude or location. This sense plays a role in the navigational abilities of several animal species and has been postulated as a method for animals to develop regional maps.
Magnetoception is most commonly observed in birds, where sensing of the Earth’s magnetic field is important to the navigational abilities during migration; it has also been observed in bacteria, fungi, insects (including fruit flies and honeybees), and animals such as turtles, lobsters, sharks and stingrays.
In many migratory animals, the light-sensitive chemical reactions involving the flavoprotein cryptochrome (CRY) are thought to play an important role in the ability to sense the Earth’s magnetic field. In the case of Drosophila, previous studies from the Reppert laboratory have shown that the cryptochrome protein found in these flies can function as a light-dependent magnetic sensor.
Wikipedia explains the effect: Evidence has also been found that the light-sensitive molecule cryptochrome in the photoreceptor cells of the eyes is involved in magnetoception.[2] According to one model, cryptochrome when exposed to blue light becomes activated to form a pair of two radicals (molecules with a single unpaired electron) where the spins of the two unpaired electrons are correlated. The surrounding magnetic field affects the kind of this correlation (parallel or anti-parallel), and this in turn affects the length of time cryptochrome stays in its activated state. Activation of cryptochrome may affect the light-sensitivity of retinal neurons, with the overall result that the bird can “see” the magnetic field.[3] Cryptochromes are also essential for the light-dependent ability of the fruit fly Drosophila melanogaster to sense magnetic fields.[4]
To test whether the human cryptochrome 2 protein (hCRY2) has a similar magnetic sensory ability, Steven Reppert, MD, the Higgins Family Professor of Neuroscience and chair and professor of neurobiology, graduate student Lauren Foley, and Robert Gegear, PhD, a post doctoral fellow in the Reppert lab now an assistant professor of biology and biotechnology at Worcester Polytechnic Institute, created a transgenic Drosophila model lacking its native cryptochrome protein but expressing hCRY2 instead. Using a behavioral system Reppert’s group previously developed, they showed that these transgenic flies were able to sense and respond to an electric-coil-generated magnetic field and do so in a light-dependent manner.
These findings demonstrate that hCRY2 has the molecular capability to function in a magnetic sensing system and may pave the way for further investigation into human magnetoreception. “Additional research on magneto sensitivity in humans at the behavioral level, with particular emphasis on the influence of magnetic field on visual function, rather than non-visual navigation, would be informative,” wrote Reppert and his colleagues in the study.
Source: University of Massachusetts Medical School
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