Activating fluorescent proteins in neurons creates a "brainbow" and will allow neuroscientists to map the brain and nervous system in a new, colourful way, Harvard University researchers have discovered.

The brainbow technique, featured in the Nov. 1 issue of the journal Nature, allows researchers to tag neurons with approximately 90 distinct colours, a vast improvement over the handful of shades currently available to scientists with current fluorescent labelling.

The variety of colours helps the scientists see the neural circuits in the nervous system more clearly, as it helps to distinguish between individual neurons.

Multicolor labelling of neurons in a 'Brainbow' transgenic mouse. Neurons of the hippocampus (dentate gyrus).
(Confocal microscopy by Jean Livet.)

"Brainbow should help us much better map out the brain and nervous system's complex tangle of neurons," said researcher Jeff Lichtman.

It could also see interactions among neighbouring non-neural cells and neurons and even help scientists identify how brain wiring reacts in many different diseases.

The technique works using the Cre/lox recombination system by shuffling the genes encoding green, yellow orange and red fluorescent proteins, assembling this transgene from snippets of DNA and inserting it into neuronal DNA.

When the DNA is inserted, the colour occurs at random, assigning up to 90 distinct colours to the neurons, and making them distinct under ordinary confocal microscopy.

"The technique drives the cell to switch on fluorescent protein genes in neurons more or less at random," explained lead researcher Jean Livet in a release.

"You can think of brainbow almost like a slot machine in its generation of random outcomes."