Transgenic animals

Creating Transgenic Animals

The creation of transgenic animals involves several key techniques:

• Microinjection: This involves directly injecting the desired gene into the pronucleus of a fertilized egg. This was the method used to create the first transgenic animal.
• Viral Vectors: Viruses, modified to be harmless, are used to deliver the gene into the animal's cells. Adenoviruses, retroviruses, and lentiviruses are commonly employed.
• Sperm-mediated Gene Transfer: The gene is attached to sperm cells, which then fertilize the egg, delivering the gene into the offspring.
• Embryonic Stem (ES) Cell-mediated Gene Transfer: Genes are introduced into ES cells, which are then injected into blastocysts (early-stage embryos). These ES cells integrate into the developing embryo, creating a transgenic animal.

Applications of Transgenic Animals

Medical Applications

Transgenic animals play a crucial role in biomedical research:

• Disease Models: Animals are genetically engineered to develop human diseases, allowing researchers to study disease progression and test potential treatments. For example, transgenic mice are used to model Alzheimer's disease and cancer.
• Drug Production (Pharming): Animals are engineered to produce therapeutic proteins in their milk, blood, or other tissues. For instance, anti-thrombin III, a blood clotting factor, is produced in the milk of transgenic goats.
• Xenotransplantation: Genetically modified pigs are being developed as potential sources of organs for human transplantation, addressing the critical shortage of donor organs. Researchers are modifying pig genes to reduce the risk of immune rejection.

Agricultural Applications

Transgenic animals offer benefits in livestock production:

• Increased Growth Rate: Transgenic salmon, engineered with a growth hormone gene, exhibit significantly faster growth rates. (AquaAdvantage Salmon - FDA approved in 2015)
• Improved Milk Production: Transgenic cows have been developed to produce milk with enhanced nutritional value or increased yield.
• Disease Resistance: Animals can be engineered to resist specific diseases, reducing the need for antibiotics and improving animal welfare.

Industrial Applications

Transgenic animals contribute to industrial processes:

• Production of Specialty Products: Transgenic sheep produce human alpha-1 antitrypsin in their milk, used to treat emphysema.
• Bioreactors: Animals can be used as bioreactors to produce valuable enzymes or other industrial compounds.

Regulatory and Ethical Concerns

The development and use of transgenic animals raise several ethical and regulatory concerns:

• Animal Welfare: Concerns about the potential suffering and health problems experienced by transgenic animals.
• Environmental Impact: The potential for unintended consequences if transgenic animals escape into the wild and interbreed with native species.
• Human Health Risks: Concerns about the safety of consuming products derived from transgenic animals, such as meat or milk.
• Intellectual Property Rights: Issues related to the ownership and control of transgenic animal technologies.

Regulatory frameworks, such as those established by the FDA and USDA in the United States, aim to address these concerns through rigorous safety assessments and labeling requirements.