Cloning genes into animals • Transgenic animal carries foreign gene inserted into its genome.
Transgenic goats Ch. 10 pg. 281 Produce human protein (drug) in milk Pharming
Transgenic animals to produce human protein in milk • Mammary gland-specific promoter • Example: Human EPO gene • Where is human EPO made in goat?
Microinjection 1. Inject gene construct into animal fertilized egg, it integrates into chromosome
2. Implant embryo into surrogate mother -> kid • How do we know if kid is transgenic (has human EPO gene in its DNA from every cell) ?
3. Transgenic kid to produces human drug – how, where? Mammary tissue specific
4. purify drug (protein) from milk • One herd can supply the world’s need • Clean, disease free Pail of milk with EPO
Spider silk (BioSteel) • The dragline form of spider silk is the strongest material known; 5 times stronger than steel and twice as strong as Kevlar. genus Araneus
Mouse model organismHHMI • Find the 4 model organisms: mice, yeast, fruit fly, nematode worm • Note the Parkinsons mouse • Where does injected foreign DNA incorporate into mouse genome • What is a pronucleus? • What is done with the mouse pup tails?
Agriculture • This pig is genetically engineered to be able to digest more and produce less manure • Other pigs produce meat high in omega 3 fatty acids
Medicine • This chicken produces a antibody in her eggs
Xenotransplantation • Pigs have similar sized organs to humans • Knock out pig cell surface antigens to prevent hyperacute rejections 100,000 in US await organ transplantation - ~ 20,000 will get organs
Fish farming • genetically engineered salmon grow faster
Patenting • Raw products of nature are not patentable. • Millions of patents • Can patent a gene, a method, an animal etc..
3 types of cloning • 1. gene cloning • Recombinant bacteria (as in lab) • Transgenic plants • Transgenic animals • 2. reproductive cloning • Yields an organism • Embryo twinning or nuclear transfer • 3. therapeutic cloning • nuclear transfer for stem cells to treat disease
Reproductive cloning Embryo twinning • 1 sperm + 1 egg - 2 embryos (genetically identical) • http://learn.genetics.utah.edu/units/cloning/whatiscloning/
http://learn.genetics.utah.edu/units/cloning/ 1. Obtain somatic cell from donor ewe Serum starve to induce Go 2. Place nucleus into enucleate egg • Somatic cell nuclear transfer videos
3. Grow embryo for 6 days in lab 4. Implant into surrogate mother 277 embryos -> 1 lamb (Dolly)
Our somatic nuclei (DNA from a differentiated cell) can be reprogrammed to embryonic state!
Cloning game http://learn.genetics.utah.edu/units/cloning/cloningornot/
Why clone animals? • Models for disease • Pharming • Endangered species – ex. Mouflon sheep, the surrogate mother was a domestic sheep! • Reproduce deceased pet • Help infertile couples?
Problems with reproductive cloning • High failure rate < 3% success rate • 2003 first horse cloned (Prometea) 22 embryos, 800 eggs • Enucleate egg may not function • Embryo may not divide • Embryo may not implant • Miscarriage
Large offspring syndrome (LOS) • abnormally large organs • Abnormal gene expression • We don’t understand how the nucleus is reprogrammed (its old DNA in a new egg!) • Telomere problems • Older DNA has shortened telomeres, some clones show lengthened telomeres
Ethical implications • Is human cloning "playing with nature?" What about in vitro fertilization or hormone treatments? • If a clone originated from existing person, who would be parents? • Social challenges a cloned child might face • Regulation
All countries have banned human reproductive cloning. Dark brown = permissive policy light brown = flexible Yellow = no federal government funding
The debate Interested in learning more: 2005 Lauren/diabetes/stem cells NOVA video 2006 stem cells NOVA video
Therapeutic cloning • Obtain embryonic stem (ES) cells 1. Isolate nucleus from a somatic cell – which? 2. Enucleate a donor egg How many chromosomes in nucleus of somatic cell? • Somatic cell nuclear transfer
3. inject somatic cell nucleus into enucleate egg • 4. Grow to blastocyst stage 3 day embryo (morula) 5 day blastocyst Cells at this stage are totipotent and undiffferentiated
Blastocyst ~ 100 cells, day 4 Hollow ball of cells with inner cell mass ICM -> embryo Blastocyst animation development in vivo
5. Take inner cell mass, transfer to flask, and ES cells reproduce. ~100 cells How do we get the cells to differentiate into what we want?
Questions • Sperm? • Fertilization? • Embryo?
Types of stem cells • Totipotent stem cells (ES) can differentiate into any cell type including placenta • Example: early embryo • Pluripotent stem cells (ES) - 5 day embryo • blastocyst cells can differentiate into any body cell type
Multipotent stem cells give rise to a number of cell types • example: stem cells in bone marrow
Sources of stem cells 1. Therapeutic cloning (SCNT) • Advantage = no immune rejection • Not dependent on transplant from another person 2. Left over in vitro fertilization embryos 3. Donated sperm and eggs 4. Umbilical cord blood, placental blood, bone marrow
Therapeutic cloning is not reproductive cloning ES cells/embryo Therapeutic cloning Cells divide to produce more ES cells Use to treat /cure disease Reproductive cloning -> Implant into female (uterus)->- birth ILLEGAL, rarely successful in animals
Uses of ES cells 1. tissue transplants – new liver cells, pancreas cells 2. Replace lost cells: Alzheimer disease, spinal cord injury, Parkinson’s disease, multiple sclerosis, diabetes, burned tissue, stroke, lung disease, heart disease, arthritis NOTE – ES cells cannot develop into a fetus – why?
A woman cannot have biological children and would like one. Her eggs are mixed with her husband’s sperm in a dish and a resulting embryo is implanted • A woman cannot have biological children and would like one. One of her nuclei is mixed in a dish with an enucleate egg and a resulting embryo is implanted
A person with diabetes is near death due to kidney failure. Even though he took insulin throughout life, the toll of the disease on his organs is critical. He is on a waiting list for a kidney transplant. • A person with diabetes uses one of his nuclei to make stem cells which are induced to form pancreatic cells in a Petri dish. His diabetes is cured at age 5.
Libraries Ch 10 • How to find a gene to clone • If sequence is known PCR • If sequence is not known library
Genomic library = Collection of clones that contain entire genome • Need > 50,000 bacterial clones to hold the entire human genome
Each colony contains different fragment of DNA • fragments unordered Need many plates
Caveats • Restriction enzymes may cut within genes • Need a lot of rbacteria to represent entire genome
cDNA library • Isolate mRNA cDNA • Coding regions only • Tissue specific