Technology.am (Sept. 15, 2009) — UCSF researchers have genetically encoded mouse cells to respond to light, creating cells that can be trained to follow a light beam or stop on command like microscopic robots.
This is the first time researchers have been able to import a light controlled “on-off switch” from plants into a mammalian cell to instantly control a variety of cell functions.
“This is a powerful tool for cell biology and cancer research, it could guide nerve cells to reconnect across a broken spinal pathway in a spinal cord injury,” said Lim, a professor in the UCSF Department of Cellular and Molecular Pharmacology.
If you have a controllable ‘light switch’ that is generic enough to use in multiple cell functions, it gives you the ability to control where and when a cell moves, using a simple beam of light, and control what it does when it gets there.
The research was carried out by Anselm Levskaya, a student in Lim’s laboratory. Levskaya initially looked to plants for proteins that might serve as the light sensor. Plants are known to rely upon light-sensing signaling proteins, to control a variety of processes.
Levskaya proposed that these phytochromes could be genetically engineered into mammalian cells and tied to a specific function.
Levskaya identified a pair of interacting proteins from plants, known as the PhyB-PIF interaction, that could be turned on and off like a switch, and then imported that cellular signaling system into live mouse cells in a cellular pathway that controls cell motion. The resulting cells can be pulled by an external beam of dilute red light, or pushed away by an external infrared beam.
They’ve been able to use similar light sensors to program bacteria and yeast cells to follow a chain of if-then commands. They have to first do this in mammalian cells, and secondly, find a method to turn them off again after they’ve performed the selected function.
The reversible aspect of his work is significant, while many methods are aimed at disrupting cellular pathways, most are fairly simple and only work in one direction: they shut a process down, or prevent two proteins from interacting, but they are limited to that one action.
This approach, by contrast, enables researchers to control precisely when the disruption occurs and for how long, then stop it at will.