Fish Story: The Coming of Biotech Animals

by Food and Drug Administration (FDA)

Potatoes with built-in insecticide. Rice with extra vitamin A. Decaf coffee beans fresh off the tree. Just when Americans have begun to digest the idea of custom-built crops, along comes another major advance in biotechnology that could make an even bigger splash onto the dinner plate: genetically engineered fish.

Using the same type of gene transfer techniques that give plants new, more desirable traits, scientists have created a genetically engineered variety of Atlantic salmon that grows to market weight in about 18 months, compared to the 24 to 30 months that it normally takes for a fish to reach that size. For fish farmers, raising these so-called transgenic fish could be faster and cheaper because it takes less feed and about half the time to produce a crop they can send to market.

Transgenic animals are just another class of products developed through biotechnology that, it is hoped, will give renewed energy to the decades-old Green Revolution. Transgenic technology promises more and better crops and food animals to feed a continuously growing world population. Genetically engineered plant crops, such as corn and soybeans, have been on the market for several years. Now, genetically engineered animals may soon begin to make their way through the regulatory net, and ultimately to the dinner table — possibly starting with fast-growing fish that the sponsor promises will begin a "Blue Revolution."

The potential benefits of transgenic animals, however, do not stop at food production. Scientists created the first transgenic animals to advance basic biomedical research, genetically modifying lab rats, mice, rabbits, and monkeys to give them characteristics that mimic human diseases. These research resources, for example, rapidly advanced the understanding of oncogenes — genes that have gone awry and are responsible for causing cancers. Moreover, researchers now seek ways to genetically modify the organs of animals, such as pigs, for possible transplantation into humans.

And finally, transgenics can turn animals, such as cows, sheep and goats, into pharmaceutical factories that produce in their milk protein-based drugs such as alpha antitrypsin, a protein that can be used to treat cystic fibrosis.

Despite these benefits, genetic engineering of animals has met with some of the same resistance already aimed at designer crops. Critics cite ecological concerns, ethical objections and food-safety issues.

But no matter how transgenics is applied, the Food and Drug Administration will play a key role in regulating the products resulting from this rapidly emerging genetic technology. This means that any drug or biologic created through transgenic techniques will need to undergo the same FDA scrutiny as any other treatment that a company wants to market, including clinical trials that demonstrate safety and effectiveness. And while it's still too soon to tell how quickly foods derived from transgenic animals will move to the market, FDA has already begun to focus on how it will ensure that they meet the same safety standards as traditional foods.

Making a Transgenic Animal

Making a transgenic animal is deceptively simple, especially when compared to traditional breeding approaches. In traditional breeding, when farmers or breeders want to introduce some new characteristic into a type of animal, they must find an individual animal that carries the desired trait. They then mate the individual to try to create a new line of animals sharing the genes that express the desired quality.

With genetic engineering, scientists possess the tools to isolate and manipulate single genes in the laboratory. In recent years, researchers have learned to insert single genes into the fertilized eggs of animals in such a way that the new gene is turned on in the resulting adult. (See "Creating A New Variety Of Fish".)

First the scientist isolates the gene that conveys a particular trait of interest-disease resistance or faster growth, for example. Then a molecular vehicle is created that will carry the gene into the nucleus of the cell and permanently integrate it into the chromosome. The entire construct — the transplanted gene, called a transgene, and its transport vehicle — might be physically injected into a fertilized egg using a glass needle viewed under a microscope. Other approaches use disabled viruses to inject the construct into the cell. If the egg survives and begins to grow and divide, then the potential embryo is implanted into a surrogate mother. Of the offspring that make it to birth, only a very small number will carry the new gene integrated in such a way that it actually functions.

But when it works, the result is a new individual of a variety of animal with a characteristic never before seen. The individual animal can then be multiplied by conventional breeding. The resulting animal may be enormously valuable. Inserting a single gene into an animal, that then manufactures a rare protein in its milk, could produce a drug that is worth many millions of dollars an ounce. The Genzyme Transgenics Corporation of Cambridge, Mass., for example, has created a goat that carries the gene for antithrombin III, a blood protein that can prevent blood clotting in people. The company purifies the protein out of the goat's milk.

But even though the medical applications of transgenics remain intriguing, the animal health and food production applications seem to be generating most of the new excitement and considerable concern.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.