Brainbow

Brainbow is a process by which individual neurons in the brain can be distinguished from neighboring neurons using fluorescent proteins. By randomly expressing different ratios of red, green, and blue derivatives of green fluorescent protein in individual neurons, it is possible to flag each neuron with a distinctive color. This process has been a major contribution to the field of neural connectomics. The technique was originally developed in 2007 by a team led by Jeff W. Lichtman and Joshua R. Sanes, both at Harvard University. The original technique has recently been adapted for use with other model research organisms including the fruit fly (Drosophila melanogaster), zebrafish (Danio rerio), and Arabidopsis thaliana. While earlier labeling techniques allowed for the mapping of only a few neurons, this new method allows more than 100 differently mapped neurons to be simultaneously and differentially illuminated in this manner. This leads to its characteristic multicolored appearance on imaging, earning its name and winning awards in science photography competitions. Brainbow was initially developed by Jeff W. Lichtman and Joshua R. Sanes at Washington University in St. Louis, though they have moved to Harvard University since then. The team constructed Brainbow using a two-step process: first, a specific genetic construct was generated that could be recombined in multiple arrangements to produce one of either three or four colors based on the particular fluorescent proteins (XFPs) being implemented. Next, multiple copies of the same transgenic construct were inserted into the genome of the target species, resulting in the random expression of different XFP ratios and subsequently causing different cells to exhibit a variety of colorful hues. Brainbow was originally created as an improvement over more traditional neuroimaging techniques, such as Golgi staining and dye injection, both of which presented severe limitations to researchers in their ability to visualize the intricate architecture of neural circuitry in the brain.