Reporter Gene Permits Tracking of Cells in the Body by MRI

Researchers working with magnetic resonance imaging (MRI) technology have used a synthetic reporter gene to track the movement of transplanted, living cells within the body.
Methods for tracking cells in vivo have been limited to magnetic or fluorescent labels. Use of these agents restricts labeling to only one type of cell at a time, while use of a fluorescent label requires removal of tissue from the body for examination under a microscope.

To avoid these restrictions, investigators at Johns Hopkins University (Baltimore, MD, USA) developed a method based on a synthetic reporter gene that was engineered to have a high proportion of lysine residues, which are especially rich in accessible hydrogen atoms. Since MRI detects energy-produced shifts in hydrogen atoms, under the appropriate radiofrequency stimulation, cells containing the engineered gene produced a natural contrast that was viewed by MRI. As specific frequencies can be processed to appear as colors in the MRI image, more than one type of cell could be tracked at the same time. Details of the new development were reported in the February 2007 issue of Nature Biotechnology.

"This prototype paves the way for constructing a family of reporter genes, each with proteins tailored to have a specific radiofrequency response,” explained first author Dr. Assaf Gilad, a research fellow at Johns Hopkins University.


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