Jeff Lichtman‘s Brainbow mouse paper is out! Not that I really need to report that news, as it is, of course, on the cover of Nature. Jean Livet comes up with some really clever genetic strategies involving incompatible, overlapping Lox sites to generate random, combinatorial patterns of multiple fluorescent proteins inside the cell. Around 90 different shades can be discerned by spectral deconvolution.
Besides making pretty covers, why is this so cool?
Well, this technique provides a method for generating high resolution maps of the brain. With a single fluorescent tag, the processes of neighboring cells blur together and became impossible to trace unambiguously. With brainbow, many neighboring axons are clearly resolvable. This is the perfect genetic tool to use for a large-scale, all-out effort for the complete mapping of the circuitry of the mouse brain. It would be a tremendous challenge, but perhaps no more difficult than the human genome project. A large public consortium, or a Celera of the brain can really attack the connectivity problem now.
Of course, there still is the more difficult problem of showing the functional connectivity of the circuit map. Then again, this technique isn’t limited to swapping in static fluorescent tags. The insert cassette could be doped with a single FP functional indicator like G-CaMP2… Would this allow the combination of static circuit mapping with functional testing?