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Arthur T Knackerbracket has found the following story:

Ultrasound can reveal a leaking heart valve, expose a torn tendon, and give parents an early snapshot of their baby within the womb. Now, researchers have shown that ultrasound can also gauge whether certain genes are switched on in animals—a feat that could one day help researchers probe everything from tumor growth to the function of nerve cells.

“It could open up a whole new way of looking at the regulation of genes,” says biomedical physicist Michael Kolios of Ryerson University in Toronto, Canada, who wasn’t connected to the study.

Cells continually turn genes on and off. To illuminate that activity—or expression—in cells, researchers can genetically modify them so that when they fire up particular genes, they also produce glowing proteins such as green fluorescent protein (GFP). Although this approach works well for cells in culture dishes, the light from these proteins doesn’t travel far in the body, making it difficult to track gene activity inside tissues and organs.

Ultrasound, which produces images by bouncing high-frequency sound waves off structures in the body, could provide a solution, says chemical engineer Mikhail Shapiro of the California Institute of Technology (Caltech) in Pasadena. The noninvasive technique, he adds, is “really great” at peering deep into tissues.

But individual cells are too small to distinguish with most ultrasound frequencies. That’s why Shapiro and his colleagues turned to aquatic bacteria that manufacture microscopic air bubbles that reflect sound waves. Inside the cells, the bubbles boost the number of sound waves that bounce back to the ultrasound device, making the host cells detectable.

An ultrasound image reveals genes are active at the edge of a mouse’s tumor.

Last year, a team that included Shapiro and Caltech bioengineer Arash Farhadi inserted 11 genes for producing the gas-filled spheres into gut bacteria and then injected the modified microbes into the intestines of mice. Using a small ultrasound probe, the scientists could pinpoint clusters of bacteria in the animals’ intestines.

Abstract: doi:10.1126/science.aaz6470

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