For those people who are allergic to cow’s milk, a solution may be on the way. Researchers from New Zealand have produced transgenic cows that are devoid of a common allergen.
Beta-lactoglobulin (BLG) is a protein that is found in cow’s milk but not in human milk. It is one of the components in milk that people could be allergic to. The functions of BLG remain unknown, and it has been generally believed that it a dispensable component of milk which doesn’t greatly alter its nutrition besides adding to its protein content. Scientists have now produced a transgenic cow that has as much as a 96% reduction in the amount of BLG.
Silencing a Gene Instead of Removing It
Earlier attempts to engineer this reduction in BLG involved removal or modification of the cow’s BLG gene in its genome. This, however, proved a very difficult process. The current method works around this difficulty using another approach. To understand this approach, let’s revisit how a protein is produced in the body. The gene for the protein is encoded in the cow’s DNA. This gene is first processed into an intermediate molecule called RNA, which is then processed into the complete protein.
The research team has added silencing sequences of DNA to the cow’s genome. These sequences are called miRNAs (short for micro-RNAs) and when expressed in the cell (by processing of their sequences), bind to the BLG RNA. This binding prevents the BLG protein from being produced. Moreover, these ‘silencing sequences’ have been inserted in such a fashion that these miRNAs are only produced when the cow is lactating. This is to minimize possible side effects. A cow cell nucleus was modified thus, and inserted into a cow egg cell, fertilized and implanted into a cow. A healthy female calf was born. This calf, strangely, had no tail. Further study is required to find out if BLG is in any way connected to tail growth in cows.
Other Allergenic Proteins Could Also Be Thus Removed
In the United States, 2 to 3 percent of infants are allergic to cow’s milk proteins. A significant proportion of these infants could benefit from hypoallergenic milk. Other proteins present in cow’s milk, such as casein, are also responsible for a significant proportion of allergies. This result highlights the potential of transgenics in coming up with solutions. Do note that lactose intolerance is induced by a different component of milk—a sugar called lactose—and is not the problem that this project addresses.
You can read about this research here.