June 23, 2008
Magnetic gene shows imaging
By Quinn Eastman
Scientists have discovered a way to force animals to make tiny magnetic nuggets inside their bodies. The technique could become a valuable tool for tracking stem cells’ movement through the body or exploring the nervous system via magnetic resonance imaging (MRI), says Emory/Georgia Tech biomedical engineer Xiaoping Hu.
“We have found a very simple way to make mammalian cells have a magnetic signature,” he says.
The results were published in the June issue of Magnetic Resonance in Medicine by Hu, graduate student Omar Zurkiya and geneticist Anthony Chan.
After the introduction of a single gene called MagA from bacteria, mammalian cells accumulate lumps of magnetite (what a compass needle is made of) a few nanometers wide, they found.
The gene MagA comes from magnetotactic bacteria, which can sense the Earth’s magnetic field. It encodes an apparently nontoxic protein that transports dissolved iron across cell membranes.
Turtles, fish and migratory birds have all been shown to have the ability to sense magnetic fields, and biologists hypothesize that they do so using magnetite embedded in parts of their nervous system.
The advantage of borrowing a gene from bacteria was that researchers had already dissected MagA’s role and it was possible to force cells to make magnetite by inserting only one extra gene rather than several.
Although Hu’s team tested MagA’s effects in human kidney cells, Hu says it will probably be most useful in transgenic animals.
“MagA can be thought of as the equivalent of green fluorescent protein, but for magnetic resonance imaging,” Hu says.
Scientists around the world use green fluorescent protein, originally found in jellyfish, to follow cells’ movement within animals’ bodies. Hu says he anticipates that MagA could find similar applications, with the advantage that magnetic fields can penetrate tissues more easily than light.