Transgenic animals
- 1. By, DAMARIS BENNY DANIEL II Msc. Zoology
- 2. A transgenic animal is one that carries a foreign gene that has been deliberately inserted into its genome. Transgenesis is the process by which mixing up of genes takes place. Foreign genes are inserted into the germ line of the animal, so it can be transmitted to the progeny. Transgenic technology has led to the development of fishes, live stock and other animals with altered genetic profiles which are useful to mankind.
- 3. First transgenic animal was a ‘Supermouse’ created by Ralph Brinster (U Pennsylvania) and Richard Palmiter (University of Washington) in 1982. It was created by inserting a human growth hormone gene in mouse genome. The offspring was much larger than the parents. Mouse – common transgenic expt. Other animals include pig, goat, cow, sheep, fish etc.
- 4. Step 1 – Construction of a transgene ◦ Transgene made of 3 parts: Pomoter Gene to be expressed Termination sequence Step 2 – Introduction of foreign gene into the animal ◦ Pronuclear microinjection method ◦ Embryonic stem cell method.
- 5. A female animal is superovulated and eggs are collected. The eggs are fertilized in vitro. The transgene containing solution is injected into the male pronucleus using a micropipette. Eggs with the transgenes are kept overnight in an incubator to develop to a 2 cell stage. The eggs are then implanted into the uterus of a pseudo - pregnant female (female which has been mated with a vasectimized male the previous night)
- 6. Transgenic animals can be created by manipulating embryonic stem cells. ES cells are obtained from the inner cell mass of a blastocyst. Transgene is incorporated into the ES cell by ◦ Microinjection ◦ By a retro virus ◦ By electroporation Transgenic stem cells are grown in vitro. Then they are inserted into a blastocyst and implanted into a host’s uterus to grow normally.
- 8. Step 3: Screening for transgenic positives ◦ Transgenic progenies are screened by PCR to examine the site of incorporation of the gene ◦ Some transgenes may not be expressed if integrated into a transcriptionally inactive site. Step 4: Further animal breeding is done to obtain maximal expression. ◦ Heterozygous offsprings are mated to form homozygous strains.
- 10. Multiple insertion – too much proteins Insertion into an essential gene – lethality Insertion into a gene leading to gene silencing Insertion into a different area can affect the gene regulation
- 12. Superfish ◦ Increased growth and size ◦ Growth hormone gene inserted into fertilized egg. ◦ Transgenic salmon grows about 10 – 11 times faster than normal fish. Glo fish ◦ GM freshwater zebra fish (Danio rerio) ◦ Produce by integrating a fluorescent protein gene from jelly fish into embryo of fish.
- 13. Alzheimer’s mouse ◦ In the brain of Alzheimer’s patients, dead nerve cells are entangled in a protein called amyloid. ◦ Mouse made by introducing amyloid precursor gene into fertilized egg of mice. Oncomouse ◦ Mouse model to study cancer ◦ Made by inserting activated oncogenes. Smart mouse ◦ Biological model engineered to overexpress NR2B receptor in the synaptic pathway. ◦ This makes the mice learn faster like juveniles throughout their lives.
- 14. Enviro pig ◦ Pigs have trouble fully digesting a compound known as phytate found in many cereal grains used to feed them. ◦ Transgenic pigs are created by introducing phytase gene of E.coli. ◦ Phytase enzyme is thus produced in the salvary gland of pig ◦ It degrades indigestible phytate with the release of phosphate that is readily digested by pigs. Pig for organ transplant ◦ Pigs with human genes, in order to decrease the chance of organ rejection by human body.
- 15. Bioreactors whose cells have been engineered to synthesis marketable proteins. More economical than producing desired protein in cell culture. Transgenic cattle ◦ Transgenic cows are made to produce proteins lactoferrin and interferons in their milk. ◦ Prion free cows resistant to mad cow disease. Transgenic sheep ◦ For good quality wool production. Transgenic goat ◦ Goats that could express tissue plasminogen activator, anti thrombin III, spider silk etc in milk.
- 16. Alba, the EGFP (Enhanced Green Flurescent protein) bunny Created in 2000 as a transgenic artwork. ANDi was the first transgenic monkey, born in 2000. “ANDi” stands for “inserted DNA” spelled backwards. An engineered virus was used to insert the harmless gene for green fluorescence protein (GFP) into ANDi’s rhesus genome. ANDi proves that transgenic primates can be created, and can express a foreign gene delivered into their genome.
- 17. Medical importance ◦ Disease model ◦ Bioreactors for pharmaceuticals ◦ Xenotransplantation Agricultural importance ◦ Disease resistant animals ◦ For improving quality and quantity of milk, meat, eggs and wool production Industrial importance ◦ Toxicity sensitive transgenic animals to test chemicals. ◦ Spider silk in milk of goat
- 18. Blurring the lines between species by creating transgenic combinations. There may be health risks associated with transgenics. There may be long term effects on the environment when transgenic animals are released into the field. Various bioethicist argue that it is wrong to create animals that would suffer as a result of genetic alteration.
- 19. Transgenic goats engineered to produce human breast milk ( Journal Transgenic Research, August 2012) ◦ University of California scientists created the transgenic goats by transferring human genes for breast milk enzymes and proteins into goat embryos. ◦ Produce 60 percent of the lysozyme and lactoferrin found in human mother’s milk. ◦ For babies of mothers who aren’t present, or can’t nurse them, milk from these transgenic goats could provide the next-best alternative. Bioluminescent transgenic mouse model for study mammary gland tumour development. (PLoS ONE, aug 2012) ◦ Research done by Cancer Biology and Therapeutics Group, Ireland
- 20. Transgenic technology is a field that is under constant evolution. Many transgenic animals have been successfully created for a variety of purposes, and the prospects are enormous. It holds great potential in many fields including agriculture, medicine and industry. With proper research and careful use the transgenic animals can go a long way in solving several problems for which science doesn’t have a solution till now.
- 21. Satyanarayana U, Biotechnology (2010), 1st edition, Books and allied (P) Ltd, Kolkata. Channarayappa, Molecular Biotechnology – Principles and Practices (2006), 1st edition, University Press Pvt Ltd, Hyderabad. Smith E John, Biotechnology (1996), 3rd edition, Cambridge University Press http://dsc.discovery.com/technology/tech-10/genetic- engineering/10-transgenic-animals-03.html www.biomedcentral.com/1471-2407/12/209 http://news.e-healthsource.com/index.php?p=news1&id=534197