The digital artists working for major movie studios like Disney and Pixar are no longer the only ones who can make outrageously-colored animals. Scientists at Duke university have genetically engineered a zebrafish to have myriad hues in its outer layer of skin, and the effect is dazzling. They call their creation "skinbow," an amalgam of the words "skin" and "rainbow."

While adding a little color to nature is nice, the real reason the researchers created the skinbow was to be able to track the activity of skin cells in real time. By altering the DNA in the skin cells, the researchers were able to make each cell fluoresce in some combination of green, red and blue. Lead researcher Kenneth Poss says that the possible color output of each cell is probably in the thousands, although his team's equipment can only pick up about 70 of them.

Still, that was enough watch the skin cells perform throughout their entire lifespan.

"Before we can fully understand tissue regeneration, we need to be able to monitor what individual cells are doing," says Poss. "This is a cutting-edge way to visualize hundreds or thousands of cells at once in a regenerating tissue." He likened the technique to being able to assign a different trackable barcode to every skin cell covering the fish.

In its experiments, the team did everything from scratching off a few cells to amputating an entire fin. Zebrafish are particularly well-suited to this kind of study because they have remarkable regenerative abilities and are relatively easy to manipulate genetically. Duke University even has a facility where researchers raise several hundred thousand of the 1.5-inch-long fish, which they feed 35 million brine shrimp daily.

As expected, the experiments allowed the researchers to be able to watch skin cells in action. In the case of the amputation, they were able to see as cells were called into action from just below the level of the cut to seal the wound. Then new cells were created and grew rapidly to begin rebuilding the fin. Some even grew in size temporarily to facilitate the process.

These images show how the skin repaired itself over the course of four days after it was exfoliated(Credit: Chen-Hui Chen et al/Duke)

"Watching these cells is how regeneration happens," says Poss. "Regeneration is the process of many cells dividing, moving, changing in shape and size. We've seen after amputating a fin that skin cells can be highly mobile; they can be recruited into new tissue as it regenerates, so they show impressive migration.

"We can observe what happens when individual cells are lost," he added. "They can leave a gap that's quickly filled by a new cell, or it can be that the cells that are spared simply remodel and close the space themselves without a new cell being produced."

The technology for skinbow came from what is known as brainbow, which is a method developed by researchers at Harvard University for using color to track individual nerves and map their connections. Just as with the skinbow, the brainbow used genetic cell modification and the incorporation of three fluorescent proteins into the DNA of the cells to make them light up in a color that was some combination of red, blue and green.

The researchers hope to combine skinbow with other imaging techniques to get an even more complete picture of the mechanisms by which skin cells operate. This could be especially useful in understanding skin disease as well as learning how drugs affect tissue growth and regeneration. Poss also indicated that the technique could one day be expanded for use on other species. Rainbow skin anyone?

The team's work with the skinbow technique is described in a paper published on March 21 in the journal Developmental Cell. Have a look at the overview video below for more information.

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