Professor’s Genetically Encoded Sensor Helps Researchers Understand Cell Quiescence

Keck Graduate Institute (KGI) Assistant Professor Alex Zambon has spent several years developing a genetically encoded sensor to identify the lifecycle phase of individual living cells in real time. Now he has been able to validate that the sensor works.

Zambon was part of a multinational research team led by Associate Professor Bing Hu of the University of Plymouth in England that used the sensor to study adult stem cells in mouse incisors. Hu thought it would be the perfect tool to help understand what drives stem cells to go into quiescence, or hibernation, and how they reenter the cell cycle, initiating the genetic program that causes cells to divide.

“It’s difficult to study why cells go into quiescence because there’s no way to determine whether the cells are quiescent or paused in the cell cycle after they have irreversibly committed to dividing. Cells can become paused while in the cell cycle for many years, but they’re not in quiescence,” explains Zambon.

“We believe the sensor is unique because it marks when cells go into quiescence.”

KGI Assistant Professor Anna Hickerson and PhD student Leomar Patam have been working on the sensor with Zambon. Hickerson developed a way to automatically highlight each cell in the images Patam captures on video using a sensitive microscope. She also wrote the code that extracts meaningful data from these images.

“If you do this by eye, you can do a few, but there are hundreds of cells on each image,” says Hickerson. “The software automatically finds the information—the number and size of cells, intensity of fluorescence, their relative positions. You can use the same method to track over time how a cell is moving, how it changes, how long it survives, and when it dies.”

Employing the sensor developed in Zambon’s KGI lab, the members of the multinational research team were able to identify the protein Prominim-1 as a new therapeutic target for cancer treatment and tissue regeneration. Their article discussing this finding, “Promomin-1 Controls Stem Cell Activation by Orchestrating Ciliary Dynamics,” recently appeared in The Embo Journal, a respected international publication focused on molecular and cell biology.

“With cancer, you want to prevent quiescence because it may go into dormancy. If a cancer cell is dividing slowly or is in a quiescent state, it evades therapy. With heart disease, cells go into permanent quiescence. You want these cells to go back into the cell cycle and cause repair,” explains Zambon.

Since proving with his international colleagues that the sensor is as useful as he envisioned, Zambon has created a more streamlined version and started using the sensor to study how cells in quiescence differ from those beginning to divide.

“We believe that the quiescent state is a cellular process regulated by specific genes yet to be defined,” he says.