Harvard scientists create colourful ‘brainbow’ images of the nervous system

November 14th, 2007 - 8:14 am ICT by admin  
The technique called ‘Brainbow’ helps tag neurons with nearly 90 distinct colours, a huge leap over the mere handful of shades possible with current fluorescent labelling.

According to the researchers, the visual resolution of individual brightly coloured neurons may greatly help scientists in charting the circuitry of the brain and nervous system.

“In the same way that a television monitor mixes red, green, and blue to depict a wide array of colors, the combination of three or more fluorescent proteins in neurons can generate many different hues,” says Nature magazine quoted Lichtman, professor in the Department of Molecular and Cellular Biology and the Center for Brain Science in Harvard’s Faculty of Arts and Sciences, as saying.

“There are few tools neuroscientists can use to tease out the wiring diagram of the nervous system; Brainbow should help us much better map out the brain and nervous system’s complex tangle of neurons,” the researcher added.

The resulting images may also enable scientists to identify how brain wiring goes awry in many different diseases, besides tracking the complicated development of the mammalian nervous system, currently understood only in general terms.

The researchers have revealed that Brainbow uses a well-known genetic recombination system known as Cre/lox in a new way, to shuffle genes encoding green, yellow, orange, and red fluorescent proteins.

During the procedure, they assembled the Brainbow transgene from snippets of DNA, and then inserted it into neuronal DNA. They found that the process assigned scores of different colours to neurons.

The researchers said that the variation of colours enabled them to observe neurons immediately under ordinary confocal microscopy.

“The technique drives the cell to switch on fluorescent protein genes in neurons more or less at random. You can think of Brainbow almost like a slot machine in its generation of random outcomes, and Cre/lox is the hand pulling the lever over and over again,” says Livet, a postdoctoral researcher in the Department of Molecular and Cellular Biology and Center for Brain Science who did much of the legwork behind Brainbow.

The researchers used Brainbow to look at mouse neural circuits over periods as long as 50 days, which enabled them to observe some neural reorganization over time, and to ascertain that Brainbow labelling was stable and long-lived.

They are now using the technique to scour the nervous system for new insights into its organization and function.

“We’ve already used Brainbow to take a first peek at the nervous system of mice, and we’ve observed some very interesting, and previously unrecognized, patterns of neuron arrangement. As far as understanding what we’re seeing, we’ve only just scratched the surface,” says Sanes, professor in the Department of Molecular and Cellular Biology and Center for Brain Science at Harvard. (ANI)

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