Scientists strip zebrafish of stripes

Within weeks of publishing surprising new insights about how zebrafish get their stripes, the same team from University of Washington is now able to explain how to "erase" these.

The findings give new understanding about genes and cell behaviours that underlie pigment patterns in zebrafish that, in turn, could help unravel the workings of pigment cells in humans and other animals, skin disorders such as melanoma and cell regeneration.

"Using zebrafish as a model, we have basic understanding of what is going on so we can start to look at some of these other species that have really different patterns and start to understand them," explained David Parichy, professor of biology and corresponding author.

Zebrafish, a tropical freshwater fish about 1.5 inches long, belongs to the minnow family and is a popular addition to home aquariums.

Adults have long horizontal blue stripes on their sides, hence the reference to "zebra".

These patterns have roles in schooling, mate selection and avoiding predators.

Researchers have reported that cells called xanthophores that produce the colour orange do not come from stem cells as had long been assumed.

Instead, they come from pre-existing cells in the embryo.

According to researchers, cells in the embryo first mature into xanthophores and then, when it is time to make stripes, these same cells lose their colour, increase in number and then turn back into xanthophores with colour.

"This is remarkable because cells do not normally lose their mature properties, let alone regain them later. Knowing how xanthophores achieve this feat could provide clues to regeneration of tissues and organs without the need for stem cells," Parichy suggested.

Even more remarkably, the authors found that the re-development of orange-producing xanthophores requires thyroid hormone, the same hormone that turns tadpoles into frogs - suggesting that xanthophores undergo their own metamorphosis.

The research appeared in the journal Nature Communications.