July 8, 2013
Goats with spider DNA produce silk
Got Silk?
Researchers are spinning spider silk from goats’ milk
Spider silk and goat milk–what could possibly be the connection?
Let’s start with the spiders.
Humans love spider webs, but aren’t so crazy about their builders.
While spiders make some people flinch, there’s no escaping the appreciation for their masterful web construction.
“There’s a lot of interest in spider silk fibers because they’re stronger than almost any other manmade fiber and they’re also elastic,” says Randy Lewis, professor of molecular biology at the University of Wyoming in Laramie.
Since ancient times, there’s been a fascination with spider webs because of that combination of qualities. There’s folklore going back to the first century A.D., when spider webs were used as dressings for wounds. Twenty-first century experts are looking at silk for many of the same reasons.
“So there are a lot of applications,” continues Lewis. “People are interested in them for things like artificial ligaments and artificial tendons, bulletproof vests and even car airbags–something that would allow you to be contained, but not blown back in your seat.”
But, whether it’s for super-strong sutures for surgery or an air bag, how do you come up with enough raw material? Spider farms have been tried, but arachnids tend to kill each other.
“The problem is that the spiders are territorial, and so no matter what you do, there are only a certain number of spiders you can put in a certain space,” says Lewis.
That’s where the goats come in.
With help from the National Science Foundation (NSF), Lewis and his team have figured out a way to put the spider’s silk-making genes into goats.
“So what we’ve done is we’ve actually cloned the genes for the protein that makes up every one of the spider silks. They make six different kinds of silk and a kind of glue. We know, in particular, (there is) a silk called dragline silk that they use to make the framework of a web, that’s the one that most people are interested in,” he explains.
Lewis, working with Nexia Biotechnologies, has put those silk genes in goats, in a way that they only make the protein in their milk.
“When the goats have kids, and they start lactating, we collect the milk, and we can purify that spider silk protein in much, much higher quantities,” says Lewis.
This academic “Spiderman” is a hands-on guy, whether it’s milking goats or wrangling spiders. The halls of his labs are covered with spider balloons and posters of the Spiderman from comic book fame. There are also crayoned, thank you notes from school children who have seen some of the spiders up close.
At the University of Wyoming Animal Science Livestock Center, a few miles from the main campus, Lewis is surrounded by seven lively and inquisitive kids, but these kids are goats that were born in early February 2010.
“We had three sets of twins and one single. We’ve done the blood tests on them, so we know that three of them do have the silk gene, and four of them do not. There are only so many copies of the gene, so it’s like any other genetic factor, a certain percentage is going to get it, and some of them aren’t,” he explains.
So far, Lewis has not seen any differences in the health, appearance or behavior in the transgenic versus the “regular” goats.
“In lots of ways, these goats are a lot more pampered because they are very valuable,” he notes.
Lewis knows that the topic is a little baffling, but says with the appropriate explanation, even youngsters can have an understanding of the research. The cool spiders and adorable baby goats help!
“We go to preschools, we take spiders and we talk about what we do. We talk to senior citizens at Rotary and Kiwanis clubs. So from 3- or 4-year-olds to 90-year-olds, I think most people can understand the kinds of things we are doing. They may not understand the details, but I think they get an idea; they understand about spider silk and they know that it’s strong, and they understand that you can’t just farm spiders, so you’ve got to come up with another way to make the material. And, I think they appreciate that,” says Lewis.
Chemical engineer Heather Rothfuss says she never could have imagined the spider-goat combo before she began work on this project. She also educates the community as well as her students at the university about the research.
She recently took one of the large golden orb weaver spiders to her son’s preschool.
“Most of the kids held her; the teachers were terrified,” laughs Rothfuss.
Rothfuss says explaining the genetic engineering aspect of the project is important, since there are critics of such procedures.
“They may have opposition to different things but it’s nice when it’s based in reality,” she says. “When people think you’re doing ‘the Frankenstein thing,’ just out of scientific curiosity, then there’s a lot of anger involved. But once you start talking about applications, people warm up. My students talk a lot about ethics and scientific implications.”
Many of the applications for spider silk involve medical problems. The silk could be used for eye sutures, as well as for certain facial injuries. There is even research on jaw repair, especially for veterans returning home from Iraq and Afghanistan.
“These jawbone injuries are hard to heal as the jaw repair material has to be strong enough to allow use of the jaw during healing,” Lewis explains. “Current materials have to be too thick to work so, by adding spider silk proteins to them, we hope to make them thin enough.”
Even larger quantities of the silk might someday be produced if the silk genes can be introduced into alfalfa plants.
“We chose alfalfa for a couple of reasons,” says Lewis. “One is it’s produced and widely distributed across the country, so there’s a good system for being able to harvest it and transport it. The other thing is alfalfa produces a pretty high protein content. It is 20-25 percent protein, so we think it’s an ideal crop for this use.”
And after extracting the silk protein from the alfalfa, the rest of the alfalfa plant could be used to make ethanol.
It may take a few more years before your doctor calls for the “spider silk suture” for a joint replacement or an organ transplant. But it takes awhile to catch up to the 400 million years spiders have had to perfect their spinning skills!