Bài giảng Nhập môn công nghệ sinh học - Animal Biotechnology

cts of surrogate mothers at end of day 4. 
Procedure for Producing Transgenic Mice 
Second breeding pair: 
Sterile male + surrogate mother 
Sterile male produced through vasectomy 
Surrogate mother must mate to be suitable recipient of injected eggs 
Mated on day 3 
Microinjected oocytes from first breeding pair are transferred to oviducts on day 4 
Embryos implant in uterine wall and are born 19 days later. 
Southern blotting techniques confirm presence and copy number of transgenes . 
Procedure for Producing Transgenic Mice 
Third breeding pair: 
Foster parents 
Fertile male + female mated to give birth on same day surrogate mother 
Serves as foster parent if caesarian section is required for surrogate mother 
Procedure for Producing Transgenic Mice 
Embryonic stem (ES) cells 
Pluripotent stem cells derived from the inner cell mass of the blastocyst 
Can be cultured, manipulated and then reinjected into blastocysts , 
where they can go on to contribute to all parts of embryo. 
In principle, ES cells 
also 
might be able 
to generate 
large quantities 
of any desired cell 
for transplantation 
into patients. 
Totipotent and 
pluripotent cells 
Totipotent = 
meaning that 
its potential is total . 
pluripotent = 
 they can give rise 
to many types of cells 
but not all types of cells 
(no fetus developed). 
isolated directly 
from the inner cell mass 
of embryos 
at the blastocyst stage . 
(IVF-IT surplus embryos 
 in case of humans) 
More about stem cells 
Embryonic stem cells 
Adult stem cells 
Truly pluripotential 
More restricted 
pattern of differentiation 
medical gain without ethical pain 
several countries 
have sanctioned deriving 
human ES-cell lines 
from ‘surplus’ embryos 
created through 
in vitro fertilization 
although several human 
ES-cell lines have been made, 
they will not be immunologically compatible with most patients 
who require cell transplants. 
Transgenic mice 
The growth hormone gene has been engineered to be expressed 
 at high levels in animals. 
The result: BIG ANIMALS 
metallothionein promoter 
regulated as heavy metals 
Mice fed heavy metals are 2-3 times larger 
Studies Utilizing Transgenic Mice 
“ Pharm ” animals 
(transgenic livestock) 
Bioreactors whose cells have been engineered to synthesize marketable proteins 
DNA constructs contain desired gene and appropriate regulatory sequences (tissue-specific promoters) 
More economical than producing desired proteins in cell culture 
A ntifreeze gene promoter with GH transgene in atlantic salmon 
GH gene comes from 
larger salmon 
Wild and domestic trout respond differently 
to overproduction of growth hormone. 
So in some cases, GH not effective. 
Problem with GH fish 
Transgenic salmon will escape from fisheries 
and breed with strains in the wild ? 
If the transgenic fish have 
a mating advantage (not clear) 
 and are less fit ( which they are), 
their offsprings will produce negative effect 
on the normal population. 
Solutions: 
1) To grow sterile fish 
2) To grow fish inland without chances to escape in the wild 
Improving Agricultural Products with Transgenics 
Transgenic technology holds great potential in agriculture, medicine, and industry 
The benefits of these animals to human welfare can be grouped into areas: 
Agriculture 
Medicine 
Industry 
1. Agricultural Applications 
Breeding 
Traditional cross breeding have been used for ages to create chickens, cows, pigs etc. 
Farmers 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. 
Researchers have now used gene transfer to improve the productivity of livestock. 
Now it is possible to develop traits in animals in a shorter time and with more precision. 
It also offers farmers an easy way to increase yields. 
Scientists can improve the size of livestock genetically. 
Transgenic cows exist that produce more milk or milk with less lactose or cholesterol. 
Transgenic cows have been used to produce milk which are richer in proteins and lower in fat. 
B) Quality 
Herman, a transgenic bull carries a human gene for Lactoferrin (gene responsible for higher iron content) 
Pigs and cattle that have more meat on them. 
Sheep that grow more wool. 
Eggs can be made healthier with high quality protein. 
C) Disease resistance 
Disease-resistant livestock is not a reality just yet. 
But there has been improvement in disease reduction in animals. 
The Foot- and- Mouth disease in England in 2000 led to destruction of herds of cattle, sheep and goat. 
Scientists 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. 
Transgenic disease protection promises a long term cost effective method of battling animal diseases. 
2. Medical Applications 
Xenotransplantation 
Transplant organs may soon come from transgenic animals. 
B) Nutritional supplements and pharmaceuticals 
Products such as insulin, growth hormone, and blood anti-clotting factors may soon be or have already been obtained from the milk of transgenic cows, sheep, or goats. 
The first transgenic cow (Rosie ) produced human protein-enriched milk at 2.4 grams per liter . 
This transgenic milk is a more nutritionally balanced product than natural milk and could be given to babies or the elderly with special nutritional or digestive needs. 
A transgenic cow exists that produces a substance to help human red cells grow . 
C) Human gene therapy 
Human gene therapy involves adding a normal copy of a gene ( transgene ) to the genome of a person carrying defective copies of the gene. 
Finland produced a calf with a gene that makes the substance that promotes the growth of red cells in humans . 
3. Industrial Applications 
: 
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 microsutures , and tennis racket strings. 
Biosteel is an extraordinary new product that may be soon used in bullet proof vests and in suture silk for stitching wounds. 
Animals have been used as “Bioreactors” to produce proteins. Genes for desired proteins are introduced via transgenics to the target cells . 
: 
The target cells are cloned and several such cells are raised into adults. 
These adults may produce milk or eggs (due to the presence of introduced gene rich in desired protein). 
Toxicity-sensitive transgenic animals have been produced for chemical safety testing. 
Microorganisms have been engineered to produce a wide variety of proteins, which in turn can produce enzymes that can speed up industrial chemical reactions . 
Transgenic animals have been used to produce pharmaceutical protein: example a human gene called AT III has been transferred to goats. 
Goats milk contain this protein that prevents blood clotting (goats multiply faster than cows) 
“Hen bioreactor” eggs are used to enrich protein by recombinant DNA technology . 
Transgenic Goats That Produce Valuable Proteins in Their Milk – “Biorectors” 
Transgenic Models in Drug Development 
Search for new drug targets 
Validation of drug targets 
Safety testing 
Protein production 
Unexpected Phenotypes 
Phenotype more severe than expected : 
Early lethal 
Lack of inductive signals 
Phenotype less severe than expected : 
Incomplete gene disruption 
Genetic redundancy 
Functional redundancy ( compensation ) 
Models for Target Validation 
Disease Models 
Reporter mice to monitor gene expression 
Mice with human drug targets ( eg . knock-in mice ) 
What are the ethical concerns surrounding transgenesis ? 
	 Ethical concern is ever increasing as the technology grows, including the issue of lab animal welfare 
These ethical issues include questions such as: 
Should there be universal protocols for transgenesis ? 
Should such protocols demand that only the most promising research be permitted? 
Is human welfare the only consideration? 
What about the welfare of other life forms? 
Should scientists focus on in vitro (cultured in a lab) transgenic methods rather than, or before, using live animals to alleviate animal suffering? 
A S ummary of Animal Cloning 
Although there has been limited success in cloning some animals, it's still seen as a viable technology. 
Ever since the announcement of the birth of Dolly, additional sheep, cows, goats, pigs , and mice have been cloned. 
: 
There are still obvious problems as evidenced from the numerous deaths of cloned animals that occur just before or after birth. 
Cloning is a big first step. Genetic manipulation of cloned animals is the future direction of the cloning frontier . 
Cloning can produce genetically identical laboratory animals which can be used as models for human disease. 
No live dog clones have yet been reported, the company PerPETuate , Inc. (Connecticut) is freezing tissue from family pets for the future. 
Cloned Kittens 
4-month-old cloned cats in 2004 (CA, US). 
: 
The cloning of human embryos for reproductive purposes is illegal at this time. 
I t is still important to examine the consequences and the likelihood of this scenario. 
I dentical twins illustrate that being genetically identical does not remove their humanness . 
At any rate, there have been significant difficulties with cloning primates, including an extremely low success rate and a high number of abnormalities. 
These results make it unacceptable to attempt human cloning at this moment in time. 
Cloning has opened many doors that could lead to remarkable medical advancements but, as with all new technologies, it will be accompanied by ethical and social dilemmas .