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Brainbow is a genetic cell-labeling technique where hundreds of different hues can be generated by stochastic and combinatorial expression of a few spectrally distinct fluorescent proteins. Unique color profiles can be used as cellular identification tags for multiple applications such as tracing axons through the nervous system, following individual cells during development, or analyzing cell lineage. In recent years, Brainbow and other combinatorial expression strategies have expanded from the mouse nervous system to other model organisms and a wide variety of tissues. Particularly exciting is the application of Brainbow in lineage tracing, where this technique has been instrumental in parsing out complex cellular relationships during organogenesis. Here we review recent findings, new technical improvements, and exciting potential genetic and genomic applications for harnessing this colorful technique in anatomical, developmental, and genetic studies. [ABSTRACT FROM AUTHOR]

The global mechanisms that regulate and potentially coordinate cell proliferation & death in developing neural regions are not well understood. In particular, it is not clear how or whether clonal relationships between neural progenitor cells and their progeny influence the growing brain. We have developed an approach using Brainbow in the developing zebrafish to visualize and follow multiple clones of related cells in vivo over time. This allows for clear visualization of many dividing clones of cells, deep in proliferating brain regions. As expected, in addition to undergoing interkinetic nuclear migration and cell division, cells also periodically undergo apoptosis. Interestingly, cell death occurs in a non-random manner: clonally related cells are more likely to die in a progressive fashion than cells from different clones. Multiple members of an individual clone die while neighboring clones appear healthy and continue to divide. Our results suggest that clonal relationships can influence cellular fitness and survival in the developing nervous system, perhaps through a competitive mechanism whereby clones of cells are competing with other clones. Clonal cell competition may help regulate neuronal proliferation in the vertebrate brain. [ABSTRACT FROM AUTHOR]