IT’S Christmas…and half the world is wearing woolly jumpers sporting gaudy reindeer patterns. We all receive them from our nearest and dearest, and we all have to wear them to please – at least until we sneak them into the hot wash and shrink them. Shrinkage is just wool’s way of helping us escape bad fashion, even if it also means we have to dry-clean our trendy wool suits.
But it could one day be a distant memory. żěè¶ĚĘÓƵs in Australia are hard at work concocting the sheep of the future: non-shrink sheep that will stride confidently out into the rain and snow and more importantly, will produce non-shrink, fully washable wool garments that will let you and me do the same.
What’s more, the sheep of the future could also be engineered for less scratchy wool. Indeed, they could be tailor-made to produce wool with any property you want: blue, green, stretchy, even glow-in-the-dark. Most shocking of all, the quest for high-tech wool might one day see sheep themselves getting the chop, to be replaced by sheep-free wool that’s grown like shag carpet in the factory.
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Wool’s shrinkiness stems from its microstructure. Each fibre is wrapped in protein scales like overlapping roof tiles. When it gets wet, the fibre’s innards soak up water and swell, pushing the scales out like saw teeth. Shrinkage occurs when the swollen, saw-toothed fibres slide against each other. “It’s a ratchet effect,” says Tony Schlink, a wool biologist at CSIRO Livestock Industries in Perth, Australia. “A fibre can only move in one direction, and that allows it to wrap around another fibre more and more tightly.” Multiply this effect by millions of fibres, and you get a jumper that’s shrunken – reindeer and all.
Schlink and colleague Johan Greeff of the Department of Agriculture in Katanning, Western Australia, want to grow wool that’s more shrink-resistant. They screened 3000 sheep, swishing a small sample of wool from each one in water and then measuring how tightly it contracts, or felts, into a ball. Surprisingly, they found shrinkage varies widely from sheep to sheep. “When you adjust for all known environmental factors that might affect shrinkability,” says Greeff, “the variation that’s due to genetics is 38 per cent.” They now plan to interbreed their low-shrink sheep in the hope of getting even more shrink-resistant wool. According to Greeff’s calculations, breeding could initially reduce shrinkage by 1 per cent per year.
Of course there are even more drastic ways of engineering wool. George Rogers, a biochemist at the University of Adelaide in South Australia, has tinkered with the elastic properties and feel of wool by making transgenic sheep with altered genes.
This is no simple affair; the wool fibre’s innards are as intricately woven as a Persian rug. In some parts of a fibre, ropes of protein called filaments form hexagonal rods, while in other parts, the filaments assemble into sheets that wrap round and round like cloth on a spool. These filament proteins contain springy structures that give wool its elasticity, while its strength comes partly from other proteins called matrix proteins, which glue the filaments together.
Rogers has identified a handful of the 30 or more filament and matrix proteins in wool, and created transgenic sheep that produce extra amounts of one protein or another. The results, as might be expected with preliminary work, were mixed: some fibres that were softer to handle turned out to be weaker as well.
Wool-market fluctuations and anti-GM sentiment have dried up transgenics funding for the moment. But once wool’s structure is better understood, there is no end to the mischief you could wreak through transgenics, including some things you certainly couldn’t do through down-and-dirty breeding.
Surgically precise mutations in the scale proteins could blunt the saw tooth and reduce shrinking. Incorporating elastin, the protein that makes our arteries springy, into the wool fibre might yield, straight off the sheep, super-stretch wool to rival spandex. And while you are dressing sheep in slinky spandex, you might as well make them blue or glowing green too: it’s only a matter of incorporating DNA sequences for the right proteins into the genes encoding wool’s building blocks.
“People have produced green rabbits with a green fluorescent protein. I’ve thought of doing it in sheep,” Rogers confides. “And if you deposit a protein called haemocyanin in the wool, it might give it a blue colour.”
The flock of the future could look like a group of blue-rinsed old ladies fresh from the hairdresser. But wool’s resemblance to human hair does not stop at colour – wool and human hair follicles are very similar too. And research into wool is starting to profit from the millions that have been poured into the search for a cure for baldness. One benefit could be the disappearance of wool’s trademark itchiness, which gets worse as the fibres get thicker.
Fleece with more than 5 per cent of fibres thicker than 30 micrometres across feels scratchy, while finer-fibred fleece feels progressively softer. Wool growers have long bred for finer wool, but a controversial new theory could revolutionise their efforts by allowing breeders to predict the fineness of an animal’s wool while it is still in its mother’s womb.
Follicles appear on fetal skin in two main waves. The first ones pop up in a regular square pegboard pattern and produce relatively coarse fibres. The second-wave follicles develop haphazardly, branching into progressively skinnier follicles that grow finer fibres. As the density of follicles on the skin increases, the diameter of the fibres they produce falls. It’s as if any given piece of skin can produce only a certain cumulative thickness of wool, regardless of how many fibres it is divided into.
This has led Phil Moore of the University of Western Sydney to propose that fetal skin harbours a limited number of “founder cells” that can initiate follicles, and the more of these cells that go into a follicle, the coarser the resulting fibre. It appears his hunch is correct. Researchers studying human baldness have identified descendants of these founder cells, called papilla cells, in each hair follicle. If injected into skin, these cells can sprout new follicles. Moore has found that, in sheep, the more papilla cells in a follicle, the coarser its wool fibre.
So to produce finer fibres you’d have to influence the number of cells going into first-wave and second-wave follicles. “If more founder cells are left over to form the secondary follicles,” says Peter Wynn of the University of Sydney, “you end up with a more even population of follicles, the primary follicles being the same size as the secondary follicles.”
Increasing the branching of secondary follicles should also reduce fibre thickness. Wynn and Moore are collaborating to identify the founder cells and follow them through fetal development. They are aiming to identify genes that push founder cells to produce more secondary follicles, and genes that make these follicles branch more often and grow finer fibres. These genes could then be screened for and tracked in breeding programmes. Eventually, they could even be modified by transgenics.
And the genetic tinkering needn’t stop there. For years money has been poured into finding a way to grow new hair follicles to replace the old ones that are sputtering out on the shiny heads of balding men. The successful cloning of follicles could very well usher in the unthinkable: a brave new world of sheep-free wool which is grown by the metre in high-tech factories. And those outmoded sheep could be put out to pasture once and for all.
“The wool follicle is amazing,” says Wynn. “You can quite happily dissect out a follicle, float it on growth media with a couple of hormones, and grow a fibre for eight days.” The wool follicle is such an autonomous, self-sufficient organ that it will scrape together whatever nutrients it needs from its surroundings – wherever you put it. Large-scale production might mean culturing a “lawn” of dermal cells, then seeding this with immortalised papilla cells.
We are a society obsessed with hair – keeping it, removing it, or colouring it. Wool made to order by the metre somehow seems inevitable. It’s just a shame it won’t stop you receiving those tasteless Christmas jumpers.