26 February 2007

Medicine – the udder alternative

High tech genetics is turning pharm animals like cows, sheep and chicken into living medicine factories. We take a look at how it works.

Much like corn crops are being used to produce bio fuels, farmers may soon be putting their cows, sheep and chickens to new unexpected uses.

Producing certain medicines using traditional methods is a very slow and expensive process. But, instead of struggling with tricky chemistry and complicated lab work, scientists are finding ways to let so-called pharm animals get the job done.

Through a clever bit of genetic manipulation, a cow's milk, or the white of a chicken’s egg, can be made to contain certain hard-to-find proteins. These proteins can then be used to make medicines to treat people whose bodies do not naturally produce enough of the particular protein.

How it is done
The key to getting a cow or a chicken to produce a specific protein is to introduce the gene that codes for that particular protein into the cow's genome. Put another way, scientists have to smuggle the recipe for making the medicine into the animal’s body.

They do this by injecting the human gene into a fertilised cow embryo. If everything goes to plan, the cow will grow up with this human gene as part of his genetic make-up. Animals that contain human genes, or genes from any species beyond their own, are called transgenic animals.

Since the human gene will be present throughout the cow’s whole body, scientists needed to find a way to restrict the expression of the gene to the cow’s udder. After all, we do not want the human protein to be produced in the cow’s heart or brain, where it may do harm.

Scientists overcame this difficulty by tying the human gene to a DNA signal, also called a promoter. In this case, the DNA signal is only present in the udder, and therefore the protein will only be produced in the udder. Thus, even though the gene is present in the cow’s brain, it will not be expressed there, since the signal is absent.

Since successfully introducing a gene into an embryo can be quite a tricky process, scientists were quite understandably looking for a shortcut. And, the shortcut has come in the way of cloning.

Once a cow is successfully producing pharmaceutical milk, rather than starting the gene insertion process from scratch each time, the cow can simply be cloned.

Medicines made in this way
Once the genetic manipulation has been done successfully, all that remains is to milk the cows and extract the required proteins.

It may sound like science fiction, but a blood clotting medication derived from transgenic cows has already won approval in Europe. And future drugs for cancer, haemophilia, anaemia and emphysema may well follow.

Whereas the potential of transgenetically produced medicines are certainly substantial, there are concerns over the well-being of the animals involved. If something goes wrong during the process of inserting a gene into the embryo, an animal may well sustain permanent genetic damage.

Furthermore, the prospect of rows of cloned sheep, chickens or cows churning out enriched milk may well be of concern to some animal rights groups. How it will play out is still unclear, but ten years from now, you may well be paying a few rand extra for free-range pills. – (Health24)


Genetic Science Learning Centre (University of Utah)
Wired News

Read more:
Genetics Centre
Gene therapy – what you need to know

February 2007


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