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Different cells have different talents
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But - all came from one
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How do cells
differentiate?
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Some cell types continue to replace
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Other cell types slow down or stop replacing
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If an organ malfunctions, we might replace it, but….
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Brain & spinal cord: no regrowth, no transplant
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Defects in development when cell differentiation goes wrong
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Cancer is cell differentiation gone wrong
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How do cells
differentiate?
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Original cell has a complete set of DNA directions
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Every differentiated cell has all the DNA directions
…but they’re stuck.
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All the genes are there, but only a few are switched on.
Control this, you control differentiation..but how?
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Microarray technology detects switched-on genes
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All the genes are there, but only a few are switched on.
Control this, you control differentiation!
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Bone marrow the first known “stem cells” -they’re multipotent
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Early embryos have pluripotent cells
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Very earliest embryo cells are TOTIPOTENT
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Nov 1998: Stem cellsGrown from Human embryos
John Gearhart, Hopkins
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Scientists’ Benefit: replacement of diseased tissues
Public’s Concern: sacrifice of embryos
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Adult stem cells produce neurons, heart cells,etc.
Nov 2000
QuickTime™ and aGIF decompressor
are needed to see this picture.
Q. Decision-makers:Can’t we use adult stem cells instead of embryos?
A. Most scientists say “we need both!”
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Scientists repair damage from heart attack using adult bone marrow stem cells
Mar 2001
x
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Bush approves limitedEmbryonic lines
Aug 2001:
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Some of the promise of adult stem cellsNot panning out
2004
x
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Exciting research gone elsewhere
2004
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January 2005: All cell lines contaminated
Non-human Sialic acid Neu5Gc
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Caveat: stem cell side effects
the case of the sensitive rats
Feb 2005
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Science has a long way to go
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