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Union of Concerned Scientists
Fall/Winter 1998

In the R&D Pipeline

Genetically Engineered Chickens

The genetic engineering of chickens may soon become easier. Nature Biotechnology reports that two labs in Scotland have surmounted a major hurdle slowing commercial development--the low rate at which foreign genes are taken up by chicken genomes.*

In the past, the procedures for obtaining transgenic chickens involved injecting foreign DNA into embryos and allowing the new genes to be randomly picked up and integrated into chicken chromosomes. This has proved to be an extremely inefficient process--less than one-half of one percent of injected embryos typically resulted in transgenic germline birds, that is, transgenic chickens that produce transgenic offspring.

The Scottish scientists obtained a 20-fold increase in insertion by injecting embryos with a special genetic element named mariner that facilitates insertion. Originally isolated from fruit flies, mariner is one of a group of elements called transposons which actively insert themselves into chromosomes. Mariner DNA codes for a transposase enzyme that cuts an opening in the chromosome and then inserts mariner.

The next step will be to determine if mariner can be used as a vector to move commercially desirable genes into chicken chromosomes.

Why engineer chickens?
The poultry industry is interested in genetically engineering chickens for disease resistance--especially desirable where poultry buildings house thousands of chickens in close confinement--and increased feed efficiency.

Pharmaceutical companies are also interested in poultry--or at least eggs. They envision a day when doctors might treat diseases or vitamin deficiencies by directing patients to eat eggs engineered to produce drugs or vitamins. Or companies might use eggs as factories from which drugs are extracted and purified.

* Another big hurdle is removing embryos from hens and then providing an environment where they will develop normally after being injected with foreign DNA.

Sources: A. Gibbins, "The chicken, the egg, and the ancient mariner," Nature Biotechnology 16:1013-14, November 1998; A. Sherman et al., "Transposition of the Drosophila element mariner into the chicken germ line," Nature Biotechnology 16:1050-53, November 1998.

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