Scientists Develop Ultrasound System That Reveals Gene Expression In The Body

Researcher Mikhail Shapiro and associates from Caltech have created a new reporter gene that allows scientists to see genetic activity using ultrasound that can penetrate deeply through tissue. The new development is a more effective alternative to a reporter gene typically used that glows green when exposed to light. The problem with the glowing reporter gene is that light doesn't penetrate tissue well.

The new ultrasound gene is the result of scientists working to develop "acoustic reporter genes" that are borrowed from a species of bacteria. The bacteria are buoyant bacteria that form and contain air-filled protein compartments called gas vesicles. Since the gas vesicles are buoyant, they show up strongly in ultrasound imaging.

To turn the genes that encode gas vesicle proteins into a reporter gene, the scientists needed to transplant a genetic program of nine genes from bacteria into mammalian cells. In this instance, the team used cells derived from human kidneys.

Simply inserting the genes for the reporter cells into the mammalian cells wouldn't work as the cells execute DNA differently. The key was using a virus as a sort of translator to trick mammalian cells into expressing a bunch of proteins. In this case, the virus tricked the cell into producing multiple genes from a shared piece of RNA. The team combined eight genes on a single piece of RNA.

The team also had to get the gas vesicles in the correct ratios for the technique to work. Solving that problem took several years. The team now has the genes working and will be able to use them to study gene expression in tumors immune cells, neurons, and other types of cells in living organisms. The team hopes that future improvements will allow doctors to use ultrasound to monitor the fate of cell-based therapeutics in people.