The advance, described in the August 6 issue of Science, allows researchers, for the first time, to simultaneously visualize the activity of multiple genes in the same cell. The combination of genes that are active in a particular cell during development determines that cell's fate--what type of cell it becomes. The advance also makes it possible to quantify how active a gene is, and even infer the genetic makeup of an organism.
"In addition to facilitating our own research on fruit fly development, there are many potential applications for this technique," says Ethan Bier, a professor of biology at UCSD who led the research team. "For example, it could be used to understand how tumors arise and grow, by revealing what genes are turned on and when. With this information, it should be possible for cancer biologists to predict how aggressive a tumor will be from its early patterns of gene expression."
"Cell fate decisions must be understood in order for any of the incredible medical potential of stem cell therapy to be realized," adds Dave Kosman, a research scientist in the Bier and McGinnis laboratories and lead author on the paper
Multiplex labeling, as the technique is called, uses RNA tagged with a fluorescent molecule to signal that a gene is turned on. When a gene is "on" it produces RNA copies--gene transcripts--of itself. The biologists designed fluorescently-tagged RNA molecules that are complementary to the gene transcripts, and bind to them like Velcro. Therefore a fluorescent beacon reveals the existence and location of the RNA gene copy.