Researchers use MRI to image gene expression

PASADENA, Calif., Dec. 23 (UPI) -- Scientists at the California Institute of Technology have developed a method of linking magnetic resonance imaging, or MRI, to gene cell expression.

Genes communicate with cells, telling them what to do, such as when to repair DNA mistakes or when to die. Genes can be turned on, expressed, or turned off, and knowing which genes are switched on or off is important to treating disease.

Scientists in the laboratory of Mikhail Shapiro, assistant professor of chemical engineering and Heritage Medical Research Institute investigator at Caltech, have developed a way to visualize gene expression in cells deep in the human body by using MRI signals.

During an MRI, hydrogen atoms in the body, mostly contained in water molecules and fat, are excited using a magnetic field. These excited atoms emit signals that are used to create images of the brain, muscle and other tissues, however, the MRI provides only anatomical images of tissues and physiological functions such as blood flow but not the activity of specific cells.

"We thought that if we could link signals from water molecules to the expression of genes of interest, we could change the way the cell looks under MRI," Arnab Mukherjee, a postdoctoral scholar in chemical engineering at Caltech and co-lead author of the study, said in a press release.

Researchers used the protein aquaporin, a naturally-occurring protein in humans that sits within the membrane that surrounds cells and acts as a gatekeeper for water molecules, allowing them to move in and out of the cell.

The study found that increasing the number of aquaporins on a given cell made it stand out in MRI images using diffusion-weighted imaging to make it more sensitive to the movement of water molecules.

The aquaporin was then linked to genes of interest to make a reporter gene, meaning that when a gene of interest is turned on, the cell will overexpress aquaporin making it look darker under diffusion-weighted MRI.

"Overexpression of aquaporin has no negative impact on cells because it is exclusive to water and simply allows the molecules to go back and forth across the cell membrane," Shapiro said in a press release. "Aquaporin is a very convenient way to genetically change the way that cells look under MRI."

This technique was successful in monitoring gene expression in a brain tumor in mice and could have the potential for clinical translation to humans.

"An effective reporter gene for MRI is a 'holy grail' in biomedical imaging because it would allow cellular function to be observed non-invasively," Shapiro said.

The study was published in the journal Nature Communications.