Controlling the growth of cells in a laboratory environment can help scientists study the movement of metastatic cancer cells or help create new therapies that regrow cells exactly where needed. Now researchers from Howard Hughes Medical Institute and the University of California, San Francisco have developed a method that uses genetically induced light switches to control cellular growth via a laser.
Researchers built the switch using a light-sensitive protein from Arabidopsis thaliana, a plant in the mustard family. Using some clever genetic engineering in living mammalian cells, the researchers delicately linked the light-responsive plant protein to mammalian proteins that regulate cell movement. In essence, they created a hybrid protein that causes mammalian cells to move in response to red or infrared kinds of light. Lim [Wendell Lim, a Howard Hughes Medical Institute researcher at the University of California, San Francisco –ed.] and his colleagues knew that cell movement begins when the right proteins arrive at the cell membrane. They reasoned that if they could link the plant phytochrome to specific regulatory proteins that cause mammalian cells to move, they might be able to develop a switch that could turn movement on or off in response to light.
They set up their system in such a way that shining red light on the hybrid phytochrome/regulatory protein would cause it to migrate to the cell’s outer membrane, where it could alter the structure of the cell’s cytoskeleton. That alteration would, in turn, cause the cell to change shape or move. In contrast, infrared light would quickly stop the migration of the hybrid protein to the outer membrane. So by toggling between the two wavelengths of light, scientists could turn cell movement on and off. Using a laser beam, which can be directed at a precise location within the cell, the scientists can sculpt cell shape down to a resolution of one micron — about one-10,000th of an inch.
By exposing the cells to different patterns of light, Lim and his colleagues showed they could control the movement of mouse connective tissue cells with great precision. Exposing a round cell to red light caused long extensions known as lamellipodia to project from its edges. In one experiment, they focused red light on only a small section of a cell, managing to induce only that small region to protrude from the bulk of the cell, as if it were melted cheese being pulled from a pizza
Full story @ HHMI: Sculpting Cells with Light
Abstract in Nature: Spatiotemporal control of cell signalling using a light-switchable protein interaction