October 2, 2012
Researchers Say Genetically Modified Cow Produces Reduced-Allergy Milk
April Flowers for redOrbit.com - Your Universe Online
Researchers in New Zealand have created a genetically modified dairy cow whose milk may not cause allergic reactions.
Two to three infants out of every hundred are allergic to a whey protein found in cow's milk called beta-lactoglobulin, or BLG. The research team from AgResearch engineered the cow - named Daisy - to produce milk that doesn't contain BLG. BLG, found in the milk of ruminants like cows but not in human milk, is a major cause of allergic reactions.
Daisy was created using the same cloning process that led to Dolly the sheep in 1996. Daisy was delivered by caesarean at the AgResearch facility. Daisy's genetic alteration slashed levels of BLG in the cow's milk to nearly imperceptible levels, but it more than doubled the concentrations of other milk proteins called caseins.
“The same milk quality (or even close to it) can not be achieved through conventional hybrid cows,” said Warren McNabb, director of research at AgResearch.
The team now plans to investigate whether or not the BLG-free, casein-laden milk will cause allergic reactions, reports Kalyan Ray of the Deccan Herald.
"First of all, we will have to determine whether the lack of detectable levels of BLG will impact on milk yield," said Stefan Wagner, a scientist at AgResearch.
Bloomberg correspondent Elizabeth Lopatto reports that the creation of Daisy builds on a previous technique that gives scientists precise control over which genes are active in an animal. It also gives fresh motivation to plans to engineer cows, pigs, sheep and chickens that are more resilient to diseases.
The research team genetically modified a cow's skin cell to produce molecules that block the manufacture of BLG protein. The nucleus of this cell was transferred into a cow egg cell which was grown in the lab until it formed a blastocyst. It was then transplanted into the womb of a surrogate mother.
This is not an efficient method of cloning. The scientists implanted around 100 blastocysts, with more than half the pregnancies failing early and only one viable calf, Daisy, was born. The major advance, claims the study, was demonstrating that this genetic procedure, called RNA interference, works in large animals.
Daisy, born without a tail, is ten months old. According to Ian Sample of The Guardian, the team induced lactation to produce milk for testing, and now they are waiting for natural lactation to see if it produces the high-casein / low-BLG milk naturally.
Other research groups have added or removed genes that cause allergic reactions in milk to "humanize" the milk.
"Many people have been talking about using this technique to better arm an animal to combat a virus infection, and this adds momentum to that work," Professor Bruce Whitelaw from the Roslin Institute at Edinburgh University said.
Whitelaw's lab is investigating how cows, pigs, sheep and chickens might be modified to carry genes that fight infections. The Roslin Institute used a related technique last year to create chickens that cannot spread avian flu.
The AgResearch team is now working on the question of why Daisy was born without a tail. Mostly likely, the cloning process is to blame for the birth defect, instead of the extra genes she carries.
"This congenital abnormality is rare in cows and not something we have seen in animals we have cloned previously," said Wagner. They are hoping to breed Daisy in the future.
European law regulates modified food products, including those from cloned animals. The food and milk must be assessed for safety and approved for sale before it can be marketed.
"We first of all consider our genetically modified cow a great tool to study allergenicity and do not envision any practical application any time soon," Wagner added.
The results of this study were published in the Proceedings of the National Academy of Sciences.