Unit 5: Animal Biotechnology

Animal biotechnology is a branch of biotechnology in which molecular biology techniques are used to genetically engineer animals in order to improve their suitability for pharmaceutical, agricultural or industrial applications.
Animal biotechnology has been used to produce genetically modified animals that synthesize therapeutic proteins, have improved growth rates, or are resistant to disease.
The practice of animal biotechnology began more than 8000 years ago when humans began domesticating and selectively breeding animals.
The modern era of animal biotechnology arrived following the discovery of the genetic code in the mid 1950s.
Today new tools including increased computing power, genome sequencing, cloning, regenerative medicine and direct gene insertion and manipulation have given people the potential to dramatically alter animals for a broad range of purposes, including food production, medical, and scientific research.
These advances, as well as the US Supreme Court ruling that designed life could be patented, have spawned new ways of expediting the use of animals in serving society.

Assisted Reproductive Technology

Since animals were first domesticated, many technologies have been developed to select for desirable qualities, make breeding easier, and make animals produce more offspring.

The technologies used include:

1. Artificial insemination

2. In vitro fertilization (IVF)

3. Embryo Flushing, and

4. Cloning

Many of these technologies involve the manipulation of animal reproduction.

1. Artificial Insemination

Artificial insemination refers to the introduction of semen and viable sperm into the female reproductive tract via artificial means.
Lazzaro Spallanzani, a French physiologist, was the first person to successfully demonstrate artificial insemination in dog in 1784.
Artificial insemination is widely practiced today; approximately 60% of dairy cows in the US are bred by artificial insemination.
the greatest advantage conferred by artificial insemination is the ability to quickly pass desirable traits to many offspring.
Artificial insemination is also extremely cost-efficient, as sperm can be collected and shipped all across the world.
This reduces the need for many breeding grounds to house and maintain male animals.

2. In Vitro Fertilization

IVF refers to the fertilization of an ovum by a spermatozoon outside of the body.
the first attempts at animal IVF began in the early 1930s on rabbit oocytes and spermatozoa, but were unsuccessful.
However, it was approximately 20 years later when the first successful mammalian IVF was performed using spermatozoa capacitated in vitro.
Today, IVF is still being heavily researched.
Commercially, the bovine industry has seen the greatest impact from IVF.
Hundreds and thousands of bovine embryos created via IVF are sold and exchanged worldwide each year.
This is a much more cost-efficient and bio-secure method compared to transporting live animals.

3. Embryo Flushing

Instead of fertilizing oocytes and culturing the embryos in vitro (as in IVF), embryos are often produced in vivo and then ‘flushed’ out of the uterus.
Infact, embryo flushing is much more prevalent and cost-efficient than IVF for the production of embryos.
Although the first successful embryo flush and transfer was performed in rabbits in1890, the procedure is primarily done with cattle today.

4. Cloning

An animal clone is broadly defined as an animal that originates from another animal, and both animals share identical chromosomal DNA.
Hans Dreisch created the first animal clones in the late 1800s. He created sea urchin clones by splitting a two cell embryo and allowed both cells to independently develop into sea urchins.
However, in 1996 the largest breakthrough in animal cloning came in the form of a sheep named Dolly.
Dolly became the first animal to be cloned using the nucleus of a differentiated adult cell as a donor. Cloning is also known as “somatic cell nuclear transfer” (SCNT), the technical process by which cloning is performed.
Since that time, the discussion has turned towards the possibilities of cloning human beings either for research (“therapeutic”) or reproductive purposes, and even as a potential means for organ farming.
Ethical issues specific to human cloning include: the safety and efficacy of the procedure, cloning for destructive embryonic stem cell research, and the effects of reproductive cloning on the child/parent relationship.
Some scientists are investigating the use of cloning technology as an option to save endangered species and even resurrect extinct ones.
Russian and South Korean scientists have been working together to try to clone a woolly mammoth using cells recovered from 10 000 years old frozen remains of a baby woolly mammoth.
Brazilian scientists also aim to clone endangered animals. A project designed by scientists from the agricultural research agency Embrapa, together with the Brasília Zoological Garden, will attempt to clone and hybridize jaguars, anteaters, wolves, and other endangered species.

Transgenic Technologies in Animals for Food and Other Products

Farmers have been using selective breeding to increase desirable traits in agricultural animals since the dawn of domestication.
However, the increased production potential possible from traditional selective breeding practices is limited.
Advances in molecular biology have made it possible to develop traits in animals quicker and with more precision, allowing farmers.

an alternative means to increase yields.
improve the nutritional value of food products.
make animals resistant to diseases, and.
produce human pharmaceuticals in the milk of transgenic cows, goats, or rabbits

1. AquAdvantages Salmon

AquAdvantages Salmon are in line to become the first genetically engineered (GE) nonplant food source approved for human consumption by the US FDA.
This accomplishment is the culmination of more than 20 years of work, which began in the 1980s, when Dr. Choy L. Hew, who studied an antifreeze protein that allows fish to survive subzero temperatures, was chatting with his colleague, Dr. Garth Fletcher.
They genetically engineered the salmon by attaching the antifreeze protein promoter to the growth hormone gene, causing growth hormone to be produced during the winter months, allowing the salmon to grow year round.
These fish outgrow any wild or farm-raised salmon, and can grow from the egg stage to market weight in 16−18 months, as opposed to 3 years for traditional salmon.

2. GloFish: GM Pets That BrightenHomes and Hearts

The GloFishs, a fluorescent red zebrafish, has become the first transgenic animal commercially available in the US and a really popular aquarium item.
The GloFish is available in five fluorescent colors with the exciting names − Starfire Reds, Electric Greens, Sunburst Oranges, Cosmic Blues, and Galactic Purples.
The original zebrafish (Danio rerio), from which the GloFish was developed, is native to India and Bangladesh.
The fluorescent zebrafish was primarily developed with the aim to detect pollution by selectively fluorescing when in the presence of environmental toxins.
This first fluorescent fish was created in 1999, by Dr. Zhiyuan Gong and his team at the National University of Singapore (NUS).
They inserted green fluorescent protein (GFP) gene into the zebrafish’s genome, allowing the fish to be fluorescent under natural white light and ultraviolet light.

3. Less Allergenic Milk

A team of scientists at Ag Research and the University of Waikato in New Zealand has successfully produced a transgenic cow lacking β-lactoglobulin (BLG).
This whey protein is believed to be the main cause of milk allergies in humans, and knocking out this gene could allow for the production of hypoallergic dairy products.
The researchers use miRNA technology to silence the expression of BLG in the milk, making it potentially less allergenic.
In addition, high casein levels were reported in the BLG-deficient milk • Casein makes up 80% of milk protein in conventional cows and is an extremely valuable component of milk because of its nutritional value and processing properties.
The increased casein levels associated with this BLG knockout cow could provide increased calcium levels and higher cheese yields.
In addition, another group in New Zealand has produced transgenic cows containing additional β- and ĸcasein genes.
These cows have been shown to produce milk with a twofold increase in ĸ-casein, and up to 20% increase in β-casein levels.
The increase in ĸ-casein has been associated with improved heat stability and cheese-making properties, whereas increased β-casein has been associated with increased milk calcium levels.

4. Increased wool growth in transgenic sheep

Increased wool growth in transgenic sheep has been achieved in New Zealand by introducing an insulinlike growth factor-1 gene associated with a keratin promoter.
The keratin promoter allows production of the transgene in the skin and results in an increase in the production of clean fleece weight to conventional sheep.
Although no health issues were observed in the transgenic sheep, the staple strength of the wool produced by the male transgenic sheep was lower than that of female transgenic and nontransgenic animals.

5. Silk in Milk

Transgenic goats are also being produced for dragline silk in their milk.
Dragline silk is made by orb spiders and is the strongest known material by weight.
Because of its strength as well as its elasticity, there is much interest in large-scale production of dragline silk for use in military uniforms, medical sutures, and tennis racket strings.
After failing to produce the material in bacteria and mammalian cell culture, scientists in Canada have successfully inserted the spider silk genes into goat embryos.
When the transgenic goats matured, the spider genes were expressed in the mammary glands, which began to secrete tiny strands of spider silk in their milk.
Once protocols are in place for the purification and spinning, the resulting thread could be used for a number of commercial as well as medical applications.

6. Biopharming: Transgenic Animal Advances in Medicine and Research

Transgenic animals not only have potential to improve agriculture, but could also lead to significant breakthroughs in biomedical research.
For decades proteins such as insulin and human growth hormone have been produced in bacteria and yeast cultures.
However, proteins such as Blood Clotting Factors and Monoclonal Antibodies require complex folding patterns and additional sugar molecules to become biologically active.
These sophisticated modifications require the proteins be produced in mammalian cells.
Some examples of transgenic animal systems that are currently being researched include milk, blood, and egg whites.
Transgenic animals in biomedical research can aid in the production and subsequent collection of insulin, growth hormone, blood anticlotting factors, and other biological products in the milk of cows, sheep, and goats.
Dairy cows, for example, have a yearly milk output of approximately 10,000 litres, making it possible for a single-lactating cow to produce tens of kilograms of therapeutic proteins. Relatively small herds of a few hundred lactating transgenic cows or goats can produce several hundred kilograms of purified protein per year.
It has been estimated that only 60 transgenic pigs would be needed to supply the entire factor IX protein required in the US.
This is referred to as biopharming, and is gaining momentum as a potential route for the production of products for medical use.
The first therapeutic protein produced in the milk of transgenic animals for human use was Antithrombin, an anticoagulant protein that can treat patients with a congenital deficiency.
In addition, the production of transgenic pigs whose milk contains human factor VIII and IX, hemoglobin, human protein C, human granulocyte macrophage colony stimulating factor, etc are being researched.
In addition, cows have been produced that secrete human lactoferrin, a glycoprotein involved in innate host defense, in their milk.
Because of lactoferrin’s antibacterial, antifungal, antiendotoxin, and antiviral activities, a number of medical uses for this glycoprotein have been considered, such as the treatment of infectious or inflammatory diseases.

7. Human Disease Models

An area of biomedical research that has huge potential for transgenic animals is their use as human disease models.
Although mice have traditionally been used as model for human diseases, many of the breakthroughs in mice have not translated to humans.
Because of the similar size and physiology of pigs with humans, there has been increasing interest in using pigs as human disease models.
Conventional pigs are already used to study cardiovascular disease, atherosclerosis, cutaneous pharmacology, wound repair, cancer, diabetes, and ophthalmology.
Using transgenic technology, pig models are currently being produced for Alzheimer’s disease, cystic fibrosis, retinitis pigmentosa, diabetes, and organ failure.
Once these animal models have been characterized, new drugs and therapies can be tested before clinical trials.

8. Xenotransplantation

Xenotransplantation is the transplantation of living cells, tissues or organs from one species to another.
It is estimated that 45000 people could benefit from a heart transplant each year in America, but only approximately 2000 human hearts are available.
To close this gap, researchers have begun to study xenografts, the transplanting of organs and tissues from animals into humans.
Although nonhuman primates such as chimpanzees are genetically closest to humans, reducing the chances of graft rejection, primates are endangered in the wild and their use as a source of replacement organs raises ethical concerns.
As an alternative, some have proposed using pigs as a source of organs because they have large litters, a short gestation time, are anatomically and physiologically similar to humans, and are currently used to provide some replacement tissues such as heart valves.

9. Transgenic Animals with Increased Disease Resistance

The ability to enhance disease resistance in animals holds enormous potential for the continuing field of animal biotechnology.
Currently, numerous studies are being performed to induce disease resistance in a variety of animals.
Some of the diseases being studied include mad cow disease, foot and mouth disease (FMD), porcine reproductive and respiratory syndrome (PRRS), and avian influenza viruses (AIVs).

10. Antimicrobials

Transgenic goats have been produced that make milk with the some concentration of lysozyme, the natural antimicrobial agent.
This milk helped to protect animal models against Escherichia coli and improved gastrointestinal health.
Transgenic cattle have also been produced that make human lysozyme in their milk.
Similarly, Antimicrobial peptides (AMPs) such ad Cecropin B (from the giant silk moth), has many antimicrobial effects against gram negative bacteria.
The gene encoding for cecropin B is transfected into catfish and the Asian medaka fish. Both transgenic fish breeds showed increased bacterial resistance to numerous pathogens.

Unit 5: Animal Biotechnology

Table of Content:

Introduction

Assisted Reproductive Technology