Scales, now in technicolor Chen et al./Developmental Cell 2016
Red and yellow and鈥 at least 70聽other colours. A genetically engineered fish has skin cells in all the colours of the rainbow and then some. Its beauty is more than skin deep though – the huge variation in colour could be used to track individual cells as they develop, move and regenerate.
The 鈥渟kinbow鈥 zebrafish was created using a gene that codes for red, blue and green fluorescent proteins, although only one colour is produced at a time. at Duke University in Durham, North Carolina, and his colleagues injected this gene into single-cell fish embryos. In one particular embryo, this gene became incorporated into part of the genome that patterns skin cells.
As an adult, this fish looked reddish in colour, but when the team shone a UV light on its skin, it lit up in technicolour. 鈥淲e didn鈥檛 know these patterns would develop just in the skin,鈥 says Poss. 鈥淲hen you make genetically engineered animals, you can鈥檛 fully predict the outcome.鈥
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In normal light, a skinbow zebrafish is magenta Chen et al./Developmental Cell 2016
Poss thinks that each of the fish鈥檚 skin cells has about 100 copies of the gene. Whether each gene creates a red, green or blue protein is entirely random, he says. 鈥淥ne cell might have 80 red, 10 green and 10 blue proteins, for example,鈥 says Poss. Each cell could have one of about 5000 possible colour combinations, although the resolution of Poss鈥檚 microscope only lets him distinguish 70 different colours among the cells.
Regeneration and repair
The fish and its offspring can be used to track how skin cells move to regenerate tissue and repair injuries聽鈥 a task normally made difficult by the fact that individual skin cells look so similar to each other.
In one experiment, Poss鈥檚 team took snapshots from one patch of skin, twice a day for 20 days. All the images were fed into a computer, with software that can identify and track each skin cell based on its colour. This allowed the team to work out that the entire population of the fish鈥檚 skin cells turns over every 20 days or so, and that each cell spends about eight days on the surface of the skin before it wears off.
Every cell expresses a unique combination of green, red and blue fluorescent proteins Chen et al./Developmental Cell 2016
The team also watched how the fish鈥檚 skin responds to injury. The group snipped off part of a fin 鈥 an injury that zebrafish can usually repair. Skin cells in the surrounding area raced to the injury site, and doubled in size to cover the area of the damage. Deeper down, a sheet of new skin cells was created, which rose to the surface within half an hour.
鈥淭his approach lets us image cell dynamics in a live animal,鈥 says Poss. He hopes that the skinbow fish can be used to reveal more about how tissue regeneration occurs 鈥 a process that is still mysterious, he says.
, who studies wound healing at the University of Leicester, UK, agrees. 鈥淚 can imagine that this group will be able to explore skin biology on a new level,鈥 she says. 鈥淚 look forward to seeing more research on skinbow.鈥
Journal reference: Developmental Cell, DOI: 10.1016/j.devcel.2016.02.017
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