Researchers Image Neurons As Never Before By Combining Multiple Fluorescent Prot

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Researchers Image Neurons As Never Before By Combining Multiple

Fluorescent Proteins

http://www.medicalnewstoday.com/articles/87380.php

By activating multiple fluorescent proteins in neurons,

neuroscientists at Harvard University are imaging the brain and

nervous system as never before, rendering their cells in a riotous

spray of colors dubbed a " Brainbow. "

The technique is described in the cover story of the Nov. 1 issue of

the journal Nature by a team led by Harvard's Livet, R.

Sanes, and Jeff W. Lichtman.

Brainbow allows researchers to tag neurons with roughly 90 distinct

colors, a huge leap over the mere handful of shades possible with

current fluorescent labeling. By permitting visual resolution of

individual brightly colored neurons, this increase should 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 Lichtman, professor in the Department of Molecular and

Cellular Biology and the Center for Brain Science in Harvard's

Faculty of Arts and Sciences. " 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. "

Equal parts pointillism, fauvism, and abstract expressionism, the

resulting images could also help scientists identify how brain

wiring goes awry in many different diseases. Brainbow could also

help track the complicated development of the mammalian nervous

system, currently understood only in general terms. This, in turn,

could elucidate the origins of the many brain disorders that arise

early in development.

Drawing upon a mix of genetic tricks and special proteins that cause

cells to glow, 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. The researchers

painstakingly assembled the Brainbow transgene from snippets of DNA,

and inserted it into neuronal DNA. As they predicted, the cut-and-

paste recombination occurred totally at random, in the process

assigning scores of different colors to neurons. This variation

makes neurons leap out from one another visually under ordinary

confocal microscopy.

" The technique drives the cell to switch on fluorescent protein

genes in neurons more or less at random, " 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. " 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. "

Using Brainbow to look at mouse neural circuits over periods as long

as 50 days, the Harvard researchers were able to observe some neural

reorganization over time and to ascertain that Brainbow labeling is

stable and long-lived. Livet, Sanes, Lichtman, and colleagues are

now using Brainbow 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, " says

Sanes, professor in the Department of Molecular and Cellular Biology

and Center for Brain Science at Harvard. " As far as understanding

what we're seeing, we've only just scratched the surface. "