The Spectacular Spider Goats
Transgenic Spider Goat Silk Could Change the World in a Big Way
Meet Lilly, the amazing Spider Goat. Lilly doesn’t climb walls or wear mask, and she wasn’t bitten by a radioactive spider. Her spider DNA is no accident. She was born with it. She is part of a herd of about 40 transgenic BELE and Saanan goats with a spider silk gene in their genome. Because of that gene, they create the protein that makes up spider dragline silk as part of their milk. That protein can be extracted in a lab then used to make anything from strong, flexible bullet-proof vests to a better way to transport life-saving vaccines. She may not know she’s a super goat, but that doesn’t stop her from saving lives.
Lilly and her herd live at the Utah State University South Farm Research Center. Like other dairy goats, they have a green pasture and warm barn where they are fed twice a day and milked three times a day. Unlike most dairy goats they are under 24-hour video surveillance and have three veterinarians on call at any time. Their herdsmen are undergraduate students who not only feed and milk them, but interact with them to provide some enrichment while they’re in the barn.
Dairy Goats to Spider Goats
Justin A. Jones started working with spider silk and goats as a graduate student more than 20 years ago under Randy Lewis at the University of Wyoming. He helped to create the original herd of transgenic goats in 2002. Today he heads the spider silk laboratory at Utah State University.
“You superovulate them [the goats] and collect the eggs,” he said. “Then you take a somatic cell line, so a skin cell line, from goats and you introduce the gene into the nucleus of the skin cells, and you can grow that in cell culture. Then, once you know that your gene is in there and that your cell line is happy, you can actually pull the nucleus out of that somatic cell and put it into that egg and then re-implant that into a goat that’s receptive.”
Milk, Sweat, and Tears
The lab conducted a study to look for what they call ectopic expression of the spider silk proteins. They checked to see if goats like Lilly showed any changes other than the additional protein in their milk. They found tiny amounts of the protein in the sweat glands, tear ducts, and salivary glands. “Mammary glands look very similar to salivary glands, which looks very similar to the glands that we have for tears secretion in our eyes, and sweat glands in the skin,” said Justin. “Otherwise, the goats are perfectly normal, you know, they behave the same, they eat the same, they’re just perfectly normal goats.”
Milk to Silk
The first step in the milk-to-silk process is milking the goats. Then that milk goes into a freezer. Three times a week four undergraduate students pull the milk out, thaw it, and put it through the purification process. First, they remove the fat from the milk, then filter out smaller proteins. Next, they use a method of selective precipitation called “salting out” to cause the spider silk protein to separate. They wash the resulting solid to remove the salt, whey, and any remaining non-silk proteins.
“Our solvation technique is relatively straightforward and maybe even a little bit strange. We take our purified spider silk protein, we put it in water, where we create a suspension, and then we throw it in a sealed vial and place it in a microwave.” This creates heat and pressure, the key ingredients necessary to turn the proteins into a liquid state. From there they can turn it into the fibers, films, foams, adhesives, gels, and sponges necessary to create a multitude of products.
Spider farming seems like the logical way to get spider silk, but spiders are territorial and kill each other when kept too close together. This created a need to find more cost-effective ways to create the super tough silk. In additions to goats, Justin’s lab also works with transgenic E. coli and silk worms. With E. coli, the lab goes through an intensive process to grow the bacteria and extract the silk. Silkworms produce a silk most like that of an actual spider. Goats, however, produce the raw material much greater volume. Each goat produces about eight liters of milk a day. With an average of two grams of spider silk protein per liter, that means each goat averages 16 grams of the valuable protein per day. Besides, who wouldn’t rather work with goats than bacteria or worms?
Silk to Product
Synthetic spider silk creates more products than one would think. Justin’s lab has made carbon fiber replacement from the spider silk protein. “So rather than, you know, having to use the feedstocks that you would normally use to produce carbon fiber, that aren’t that reliable, you can use this recombinant spider silk and colonize it and it actually works better than the standard carbon fiber carbon stocks.”
They’ve also created an adhesive that in certain applications works better than Gorilla Glue. However, Justin gets the most excited about medical applications. “We’ve done some vaccine stabilization studies with this goat-derived protein where you can selectively encapsulate a vaccine, for instance, in spider silk such that you no longer have to keep the vaccine cold. It doesn’t work for every vaccine, but you can imagine that would make getting a vaccine to the central parts of Africa much easier if you don’t have to maintain a cold chain. We’ve also coated intravenous catheters with our goat derived spider silk materials and it solves, or at least looks like it can solve, a number of problems with intravenous catheters such as infections, bloodstream as well as site infections, and occlusions of intravenous catheters.”
The Best Part
Although the goal is to get a product out that benefits mankind, particularly in health applications, Justin said, “I guess everybody’s favorite part is when you’ve got 40 or 50 brand new kids running around. They’re just adorable creatures.” The lab synchronizes all the does to reduce the burden the goat herdsmen, and they all birth in a really nice heated barn. These kids will be more than just friendly neighborhood spider goats, they will work for the betterment of all … and treats.
Originally published in the May/June 2019 issue of Goat Journal and regularly vetted for accuracy.