Butterflies, whales, and pigeons share a perplexing trait—they all use Earth’s magnetic field to navigate and orient themselves in space. This ability, which scientists don’t fully understand, suggests that we still have a lot to learn about how life relates to its physical surroundings.
Some scientists have argued that magnetically-sensitive proteins known as cryptochromes could help explainanimal magnetism (often called “magneto-reception”). But since cryptochromes alone can’t detect the polarity of magnetic fields, they can’t act as full-fledged compasses.
But now, a group of Chinese scientists says that they’ve found a true biological compass needle in the form of a different set of proteins that orient themselves with Earth’s weak magnetic field.
Biophysicist Xie Can of Peking University in Beijing was lead author of the study, which was published today in the journal Nature Materials. He and his colleagues claim to have found a protein in fruit flies that acts a compass needle. It’s composed of iron and sulfur atoms, and an outer layer of cryptochromes wraps around it. Xie’s team found that assemblages of these proteins align themselves in a weak magnetic field. Xie calls this biocompass MagR, for magnetic receptor.
Xie’s research could give neuroscientists a new way to manipulate individual neurons. If it works, it could serve as an alternative to optogenetics, which uses light-sensing proteins to manipulate neurons and explore how the nervous system functions.
Here’s David Cyranoski, writing for Nature News:
Xie says that in April, he submitted a Chinese patent application that includes the use of magnetogenetics and the protein’s magnetic capacity to manipulate large molecules. He is also starting to look at the structure of MagR proteins in other animals, including humans. Variants in the human version of MagR might even relate to differences in people’s sense of direction, he suggests.
But some scientists vehemently dispute the finding. Xie has not given an explanation as to how the protein actually senses magnetism or how that would get communicated to the brain. Moreover, it’s unclear whether MagR’s small amount of iron is capable of demonstrating magnetic properties. Other researchers will need to replicate Xie’s result in order to deem it plausible.
“It’s either a very important paper or totally wrong,” neuroscientist David Keays told Cyranoski.