Whether your computer screen displays a spreadsheet, a movie, or a LOLcat, you’re seeing pinpoints of light in only three colors: red, green, and blue. But by varying the relative intensity of these three components, a pixel can transform into any one of a spectrum of millions of colors. The same principle lies behind the powerful and visually spectacular Brainbow cell-labeling technique, in which each labeled cell expresses a unique ratio of three or four distinct colors of fluorescent protein. The resulting composite color can distinguish an individual cell from similar cells that surround it.
In the Brainbow approach, different copy-number ratios of each fluorescent protein transgene are achieved by stochastic shuffling of cassettes via site-specific recombinases. Depending on the strategy used, this allows between three and ~100 colors to be differentiated. The method was originally designed to trace the tangled paths of axons through the nervous system, but was rapidly adapted for lineage analyses during development.
The February issue of GENETICS features a Genetic Toolbox Review by Tamily Weissman (Lewis and Clark College) and Albert Pan (Medical College of Georgia, Georgia Regents University) that explores the evolution of Brainbow methods, provides practical tips, summarizes available genetic resources, and reflects on future directions in the field. The authors argue that the technique has opened up entirely new types of research questions because instead of being able to label only different types of cells, now we can use multiple colors within a single cell population. They also anticipate Brainbow’s potential to be combined with new genetic and genomic analyses of cells. Read the Toolbox now for an excellent overview of the field (and of course, some beautiful images!)
Weissman T.A. (2015). Brainbow: New Resources and Emerging Biological Applications for Multicolor Genetic Labeling and Analysis, Genetics, 199 (2) 293-306. DOI: http://dx.doi.org/10.1534/genetics.114.172510, http://www.genetics.org/content/199/2/293.full