Transgenesis. Stable integration of foreign DNA into host genome Foreign DNA is passed to progeny germline transmission

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1 Transgenic Mice

2 Transgenesis Stable integration of foreign DNA into host genome Foreign DNA is passed to progeny germline transmission integrates into all cells including sperm or egg Knockin mice DNA sequence is added Knockout mice a specific gene is inactivated

3 Applications Protein function Knockout gene/protein function in early embryo. What happens to animal?

4 Applications Model human disease Cystic fibrosis Cystic fibrosis is an inherited chronic disease A defective protein causes the body to produce unusually thick, sticky mucus that clogs the lungs and leads to life-threatening lung infections obstructs the pancreas stops natural enzymes from helping the body break down and absorb food.

5 Applications Model human disease Cystic fibrosis Caused by defect in chloride ion channel cystic fibrosis transmembrane conductance regulator (CFTR) Disrupt CFTR gene in mice Examine progression and pathology of disease Develop candidate therapeutics

6 Applications Model human disease Breast cancer Tumors contain activated or overexpressed proteins which can activate cell cycle potential oncogenes Tumors show deletion of tumor suppressors QUESTION: Are these mutations causative, or do they occur once tumor forms EXP: overexpress potential oncogenes in mice and examine progression of tumor.

7 Applications Model human disease Breast cancer Exp: overexpress potential oncogenes and examine progression of tumor. c-myc: transcription factor activates genes that control cell cycle elevated expression is found in some cancers elevated expression can cause cancer à oncogene

8 Applications Model human disease Breast cancer Generate mice that overexpress myc Use mammary tissue specific promoter Generate mammary tumors in mice Use general promoter Generate tumors in selected tissues not every where

9 Generation of Transgenic Mice Essential Cell Biology

10 Fertilization to Blastocyst (mouse) 1

11 Embryonic stem (ES) cells Present in the inner cell mass (ICM) Zygote Blastocyst Pluripotent (can generate all embryonic tissues but NOT extra-embryonic tissues) Proliferate rapidly in culture ICM Expansion Give rise to an entire organism when transplanted into a blastocyst 11

12 Generation of transgenic mice 1. Introduce foreign DNA into stem cell. 2. Foreign DNA integrates (recombines) into host cell genome. 3. Introduce modified stem cell into mouse embryo. 4. Introduce embryo into pregnant female. 5. Offspring contain some modified germ cells. 6. Breeding to isolate mice homozygous for foreign DNA both copies

13 Generation of transgenic mice 1. Transfer of targeted stem cell to embryo 2. Implant embryo into foster mother 3. Generation of chimeric mice some cells contain targeted gene A portion of sperm/egg contain targeted gene 4. Breed to generate mice homozygous for targeted gene.

14 Homologous recombination Pairing of complementary DNA in cell Recombine to generate new sequence of DNA Occurs naturally during meiosis Homologous Recombination

15 Homologous recombination

16 Homologous recombination

17 Gene targeting

18 Gene targeting in cells target gene sequence neomycin resistance target gene sequence target gene Homologous recombination neo r Target gene disrupted loss of gene product Cells resistant to neomycin - selection

19 Review Fig , Essent. Cell Biol.

20 Gene targeting Used to knockout gene Used to replace gene replace with GFP fusion In old days used lacz beta-galactosidase

21 Gene targeting PTPmu PTPmu gene

22 LacZ b-galactosidase X-Gal Blue

23 PTPmu found in blood vessels Laz expressed in tissues as directed by tissue specific PTPmu promoter A D Brain F B = brain H = heart SV = somatic vessels à muscles Muscles