New Fluorescent Marker Allows Detailed Study of Mitochondria in Live Cells, Study Reports

MitoPB Yellow, a new fluorescent specific marker, allows scientists to study live mitochondria, possibly leading to a better understanding of mitochondrial diseases and to new treatments, researchers in Japan report.

The marker is much more stable than current markers, and allows mitochondria to be studied for extended periods without inducing toxicity to living cells.

The study, “A photostable fluorescent marker for the superresolution live imaging of the dynamic structure of the mitochondrial cristae,” was published in the journal PNAS.

Mitochondria, the small cellular structures that produce energy for our cells, are made of an inner and an outer membrane. The enzymes that produce ATP (the molecular “currency” of energy) are located on the inner membrane. This membrane is folded into structures known as cristae, which increase its surface area.

STED microscopy is a type of super-resolution microscopy that allows a detailed look into the interior of cells. For this technique, researchers use fluorescent dyes to see the structures inside cells. But current dyes are not optimal, as they stop fluorescing with time, a process called photobleaching. This prevents researchers from observing cells over extended periods, and damaged markers can cause cells to die.

Researchers at Nagoya University’s Institute of Transformative Bio-Molecules have developed a new marker molecule, called MitoPB Yellow, which has a much longer lifespan under the microscope. This marker is specific for the inner mitochondrial membrane, making the mitochondria visible for longer periods of time.

Furthermore, the new marker allows researchers to detect structural changes of the mitochondrial inner membrane in live cells. Before, these structural changes could only be seen in dead cells.

In this study, researchers compared the MitoPB Yellow to other mitochondrial fluorescent markers. MitoPB Yellow showed greater stability — even after 50 images had been taken using the microscopy, researchers saw no significant decrease in the fluorescence intensity. Moreover, the intensity of MitoPB Yellow was maintained above 70%, the highest rating among the different mitochondrial markers.

To demonstrate the usefulness of MitoPB Yellow for imaging live cells, researchers placed mitochondria under conditions that are known to induce structural changes, which became visible using MitoPB Yellow.

Changes in mitochondria in response to deprivation of nutrients were also observed in great detail (high-resolution).

In this stressful environment, the inner mitochondrial membranes fused together both within a single mitochondrion and between neighboring mitochondria. This process may increase energy production while protecting these cellular structures from degradation.

By allowing for a more detailed study of live mitochondria, MitoPB Yellow may aid in understanding, diagnosing and developing therapies for mitochondrial disease.

“In summary, MitoPB Yellow surpasses currently used fluorescent mitochondrial markers,” the researchers wrote.

This marker may enable analysis of “the mitochondrial inner-membrane structures in living cells at unprecedented resolution,” their study concluded.