Chp 4-7 notes_wk 2 & 3 reading in Stem Cell Now

Chp 4-7 notes_wk 2 & 3 reading in Stem Cell Now -...

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Own Nts: Stem Cell Now: Chp 4, 7 Chp 4: A Brief History of ESC Discovery of  Embryonic Carcinoma Cells :  (EC) Leroy Stevens had a mouse w/ testicular cancer- bones, teeth, skin, hair, muscle in mouse’s  teratoma! o Like an embryonic stem cell gone cancerous o Some cells w/in tumor did NOT differentiate, made more clones of itself  Ex of asymmetric  differentiation o Stevens developed a way to keep EC in primordial/undifferentiated state Changing media @ specific times “Splitting” technique = dividing cells into new populations to avoid overcrowding o Injected teratoma cell  mouse embryo  cell LOST cancerous qualities  Significance: Maybe a young embryonic stem cell could “reprogram” the gene  expression of an older somatic cell o Disadvantages: EC’s had abnormal chromosomes  England lab found a way to grow ESC’s in same medium used for EC cells (invented by Leroy  Stevens’ lab) James Thompson in 1980’s used this culture to grow hESC’s Invention of  Nuclear Transfer Technique Robert Briggs used leopard frog eggs Removed nucleus from an unfertilized egg  removed another nucleus from embryo injected nucleus from embryo into enucleated egg   adult organism grew (tadpole, then frog) Significance: 1. Animal made w/OUT fertilization or sexual reproduction 2. Made a Clone of embryo 3. Transferred nuclei of one cell into a cell of a DIFFERENT EMBRYONIC developmental STAGE
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Disadvantages/Prb’s:   The greater the difference of embryo stages =  more failures   older the  embryo from where the nucleus came from = harder to get normal organism (often genetic  abnormalities)  o 0.8 % success rate o Mouse nuclear transfer HARD!   tiny blastocysts, hard to manipulate Nuclear Transfer in Sheep  =more successful b/c sheep embryos larger, easier to manipulate: same  technique as frog and mouse nuclear transfer techniques implanted nuclear transferred eggs in  surrogate moms o 1/3 success rate! o 1    st     mammalian  clone     o Steen Willadsen in Britain –  1984  At this time, few thought it was  possible to take nucleus from adult/fully differentiated cell and transfer  it to an egg (aka Somatic Nuclear Transfer was just sci-fi) SOMATIC cell Nuclear Transfer (SCNT)- DOLLY Ian Wilmut improved conditions needed to reprogram genetic expression of somatic cell’s nucleus Grew sheep udder cells in minimum nutrients, which stopped cell division of udder cells (somatic  cells) Fused udder cell + enucleated egg cell w/ electricity (not use micropipette nuclear transfer b/c too  evasive)
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