Animal Biotechnology

- What is Animal Biotechnology?- Animal biotechnology is the application of scientific and engineering principles to the processing or production of materials by animals or aquatic species to provide goods and services.

Principles of Biotechnology

Weeks 10 and 11

Animal Biotechnology

• Recombinant DNA technology now allows us to introduce foreign genes into organisms for the expression of specific new traits.

• Animals also are engineered for a variety of purposes ranging from use as human disease models to the introduction of desirable traits into a variety of economically important animals

Examples of important products that have potential include

1- human hemoglobin, which could be used during trauma when much blood is lost.Hemoglobin is more desirable than whole blood or red blood cells for transfusions, because it requires no refrigeration and is compatible with all blood types, eliminating the need for blood typing.

2- human tissue plasminogen activator, which is used to treat patients after a heart attack.

MicroinjectionThe steps involved in microinjection are:

1- Identification (and some modification such as mutation) of a foreign gene of interest

2- Insertion of the foreign gene into an appropriate vector.

3- Microinjection of DNA directly into the pronucleous of a signal fertilized egg.

4- Implantation of the microinjection egg into a surrogate mother.

5- Allowing the embryo to develop to term.

6- Demonstrating that the foreign gene has been stably incorporated into the host genome and that it is heritable in at least one of the offspring.

7- Demonstrating that the gene is expressed and regulated correctly in the host organism.

Injection of desired gene

TRANSGENIC ANIMALS AND THEIR APPLICATION

• Transgenic animals are providing many benefits. transgenic animals provide.

- Research scientists with important animal models in which to study human diseases. - Increase production (for example, eggs, meet, milk), which decreasing costs to farmer.

• generation of transgenic animals or transgenic fish (animals or fish with one or more genes introduced by human intervention),

• Production of nearly identical animals by somatic cell nuclear transfer (also referred to as clones),

• Provide healthier, more robust animals• Provide more nutritious and healthier

foods for example, lower cholesterol beef, eggs with increased vitamin E).

• Produce disease-resistant animals• Increase wool quality and quantity

• The most promising developments are transgenic animals that harbor human genes.

• These living biofactories produce important human proteins in their milk. They show promise in providing low cost, high quality pharmaceuticals and biologicals.

Transgenic

- Since the early 1980s, methods have been developed and refined to generate transgenic animals or transgenic aquatic species.

For example, 1- Transgenic livestock and transgenic

aquatic species have been generated with increased growth rates.

2- Enhanced resistance to disease .

3-Transgenic poultry, swine, goats, and cattle also have been produced that generate large quantities of human proteins in eggs, milk, in order to be used as human pharmaceuticals.

- Examples of human pharmaceutical proteins include enzymes, clotting factors, and antibodies.

How are transgenic animals produced?

• Since the discovery of the molecular structure of DNA by Watson and Crick in 1953, molecular biology research has gained momentum. Molecular biology technology combines techniques and expertise from biochemistry, genetics, cell biology, developmental biology, and microbiology.

• Scientists can now produce transgenic animals because, since Watson and Crick's discovery, there have been breakthroughs in:

• recombinant DNA (artificially-produced DNA) • genetic cloning • analysis of gene expression (the process by

which a gene gives rise to a protein) • genomic mapping

CLONINGSomatic Cell Nuclear Transfer

Another application of animal biotechnology is the use of somatic cell nuclear transfer to produce multiple copies of animals that are nearly identical copies of other animals (transgenic animals, genetically superior animals, or animals that produce high quantities of milk or have some other desirable trait, etc.).

• This process has been referred to as cloning.

• To date, somatic cell nuclear transfer has been used to clone cattle, sheep, pigs, goats, horses, cats, rats, and mice.

Steps of cloning• The CLONING technique involves culturing somatic cells

from an appropriate tissue from the animal to be cloned.• Nuclei from the cultured somatic cells are then

microinjected into a non-nucleated oocyte obtained from another individual of the same or a closely related species.

• Through a process that is not yet understood, the nucleus from the somatic cell is reprogrammed to a pattern of gene expression suitable for directing normal development of the embryo.

• After further culture and development in vitro, the embryos are transferred to a recipient female and ultimately will result in the birth of live offspring.

• success rate for propagating animals by nuclear transfer is often less than 10 percent and depends on many factors, including : A- Species B- Source of the recipient ova C- Cell type of the donor nuclei D- Treatment of donor cells prior to nuclear

transfer E- The techniques employed for nuclear transfer

etc.

Why are these animals being produced? The two most common reasons are:

• Some transgenic animals are produced for specific economic traits. For example, transgenic cattle were created to produce milk containing particular human proteins.

• Other transgenic animals are produced as disease models(animals genetically manipulated to exhibit disease symptoms so that effective treatment can be studied).

• For example, Harvard scientists made a major scientific breakthrough when they received a U.S. patent (the company DuPont holds exclusive rights to its use) for a genetically engineered mouse, called OncoMouse® or the Harvard mouse, carrying a gene that promotes the development of various human cancers.

Safety Issues and Potential Risks.

As with any new technology, animal biotechnology faces a variety of uncertainties,safety issues and potential risks.

Concerns have been raised regarding:

1- The use of unnecessary genes in constructs used to generate transgenic animals.

2- The use of vectors with the potential to be transferred or to otherwise contribute sequences to other organisms.

3- The potential effects of genetically modified animals on the environment.

4- The effects of the biotechnology on the welfare of the animal.

5- Potential human health and food safety concerns for meat or animal products derived from animal biotechnology.

Biotechnology and Cloning Animals

• Advances in biotechnology have allowed scientists to make genetically identical copies or clones of animals.

• Duplication of an organism's genome occurs naturally when identical twins are born or when a plant is grown from a cutting of another plant.

• However, the world really took notice of cloning in 1997 when a group of Scottish researchers announced the birth of Dolly the sheep, which had been cloned using a single cell from an adult sheep.

• Dolly had only one "parent;" her nuclear genome was exactly like her "mother's" instead of being a combination of two parents.

• Therefore, Dolly could generally be thought of as her mother's identical twin.

• To produce Dolly, scientists took an egg from a sheep and removed its nucleus .

• Next, they took a cell with an intact genome from a different adult sheep (Dolly's "mother") and fused it to the sheep egg which lacked a genome.

• The egg, with its new genome, was stimulated to begin developing into an embryo and was implanted into a surrogate sheep where it grew normally, resulting in the birth of Dolly.

• Dolly later gave birth to normal lambs.

What is a transgenic animal?• There are various definitions for the

term transgenic animal. • The Federation of European Laboratory

Animal Associations defines the term as an animal in which there has been a deliberate modification of its genome, the genetic makeup of an organism responsible for inherited characteristics.

• The majority of transgenic animals produced so far are mice, the animal that pioneered the technology.

• The first successful transgenic animal was a mouse. A few years later, it was followed by rabbits, pigs, sheep, and cattle.

Transgenic Goats

Martha Gomez, an assistant professor in the LSU AgCenter’s Department of Animal Sciences, and her team at the Audubon Center for Research on Endangered Species (ACRES) in New Orleans, La.,

produced the world’s first clone of an African wildcat. This clone, named “Ditteaux

methods of producing transgenic animals:

To date, there are three basic methods:• DNA microinjection • Retrovirus-mediated gene transfer

• Gene transfer by microinjection is the predominant method used to produce transgenic farm animals. Since the insertion of DNA results in a random process, transgenic animals are mated to ensure that their offspring acquire the desired transgene. However, the success rate of producing transgenic animals individually by these methods is very low and it may be more efficient to use cloning techniques to increase their numbers.

• For example, gene transfer studies revealed that only 0.6% of transgenic pigs were born with a desired gene after 7,000 eggs were injected with a specific transgene.

• 1. DNA Microinjection The mouse was the first animal to undergo successful gene transfer using DNA microinjection. This method involves:

• transfer of a desired gene construct (of a single gene or a combination of genes that are recombined and then cloned) from another member of the same species or from a different species into the pro-nucleus of a reproductive cell.

• the manipulated cell, which first must be cultured in vitro(in a lab, not in a live animal) to develop to a specific embryonic phase, is then transferred to the recipient female

• 2. Retrovirus-Mediated Gene TransferA retrovirus is a virus that carries its genetic material in the form of RNA rather than DNA. This method involves:

• retroviruses used as vectors to transfer genetic material into the host cell.

• The method was successfully used in 1974 when a simian virus was inserted into mice embryos, resulting in mice carrying this DNA.

• How do transgenic animals contribute to human welfare?

• The benefits of these animals to human welfare can be grouped into areas:

• Agriculture • Medicine • Industry • The examples below are not intended to be

complete but only to provide a sampling of the benefits.

1. Agricultural ApplicationsA- breedingFarmers have always used selective

breeding to produce animals that exhibit desired traits (e.g., increased milk production, high growth rate).

Traditional breeding is a time-consuming, difficult task. - When technology using molecular biologywas developed, it became possible to develop traits in animals in a shorter timeand with more precision. In addition, it offers the farmer an easy way to increase yields.

• B) qualityTransgenic cows exist that produce more milk or milk with less lactose or cholesterol, pigs and cattle that have more meat on them , and sheep that grow more wool.

• In the past, farmers used growth hormones to spur the development of animals but this technique was problematic, especially since residue of the hormones remained in the animal product.

• C) disease resistanceScientists are attempting to produce disease-resistant animals, such as influenza-resistant pigs, but a very limited number of genes are currently known to be responsible for resistance to diseases in farm animals.

• 2. Medical ApplicationsA) xenotransplantation:Patients die every year for lack of a

replacement heart, liver, or kidney. For example, about 5,000 organs are needed each year in the United Kingdom alone. - Transgenic pigs may provide the transplant organs needed to alleviate the shortfall.

• B) nutritional supplements and pharmaceuticals:Products such as insulin, growth hormone, and blood anti-clotting factors have already been obtained from the milk of transgenic cows, sheep, or goats.

3. Industrial ApplicationsIn 2001, two scientists at Nexia Biotechnologies in Canada spliced spider genes into the cells of lactating goats. The goats began to manufacture silk along with their milk and secrete tiny silk strands from their body by the bucketful.

• By extracting polymer strands from the milk and weaving them into thread, the scientists can create a light, tough, flexible material that could be used in such applications as military uniforms, medical micro sutures, and tennis racket strings.

What are the ethical concerns surrounding transgenesis?

• Ethical concerns must be addressed as the technology grows, including the issue of lab animal welfare.-ethical decision-making cannot be ignored by the biotechnology industry, scientists, policy-makers, and the public.

These ethical issues, raise questions such as:

1- Should there be universal protocols for transgenesis?

2- Should such protocols demand that only the most promising research be permitted?

3- Is human welfare the only consideration? What about the welfare of other life forms?

4- Should scientists focus on in vitro (cultured in a lab) transgenic methods rather than, or before, using live animals to alleviate animal suffering?

5- Will transgenic animals radically change the direction of evolution, which may result in drastic consequences for nature and humans alike?

6- Should patents be allowed on transgenic animals, which may hamper the free exchange of scientific research?

Benefits and Risks of Cloning

• Researchers have cloned other mammals including cows, goats, pigs, and mice. However, the overall low rate of successful cloning and frequent occurrence of developmental abnormalities in cloned animals demonstrate the need for further research before cloning will be practical.

• It has also been reported that cloned animals may exhibit health problems throughout their life.

• Cloned animals may age prematurely as Dolly was diagnosed with arthritis at a seemingly young age and cloned mice had a shorter than normal life span.

• Additionally, it was demonstrated that cloned mice were both larger in size and heavier than a control group of non-cloned mice.

• Breeding companies could sell cloned embryos in a manner similar to the way in which semen is currently marketed.

• A potential drawback of this practice would be the loss of genetic diversity in livestock.

• It has also been proposed that cloning could be used to increase the population of animals in an endangered species. The mouflon sheep, which is a wild Mediterranean sheep with less than 1000 animals remaining, was successfully cloned.

Conclusion• Interestingly, the creation of transgenic animals has

resulted in a shift in the use of laboratory animals such as :

• The use of higher-order species such as dogs to lower-order species such as mice.

• Decreased the number of animals used in such experimentation, especially in the development of disease models.

• This is certainly a good turn of events since transgenic technology holds great potential in many fields, including agriculture, medicine, and industry.