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Bi 1 “Drugs and the Brain”
Lecture 24 Tuesday, May 23, 2006
Cell cycle, Stem Cells, and Stem Cell Therapy
(Thanks to Prof David Anderson for some of the slides)
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Bi 1 in the next 2 weeks (for undergraduates)
Tuesday, May 23. Lecture 26. Cycle Cycle / Stem Cells
Problem Set 8 posted. Parkinson’s disease, stem cells, cell cycle
Thursday, May 25. Lecture 27. Evolution 1: Molecular Biology.
Thursday-Friday, May 25/26. Section meetings as usual. 5:30 Fri Undergrad BBQ
Monday, 5/28. Memorial day, no lecture.
Tuesday, 5/29. Lecture 28. Evolution 2. The eye.
Problem Set 8 due, 11 AM (seniors too)
Thursday 6/1. Lecture 29. Last lecture.
Evolution 3. Voyages to the Galapagos; the Physiology of Diving.
Final exam review Session: 4 PM here, 119 Kerckhoff
Thursday 6/1: Final Exam posted
Thursday-Friday 6/1-2 Section meetings as usual
Friday 6/9. Final exam due 4:30 PM, Bi 1 closet.
for the “official word”, see http://www.its.caltech.edu/~bi1/schedule.html
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mitosis
gap1(growth1)
DNAsynthesis
gap2(growth2)
mammals24 h
yeast 90 min
based on Little Alberts 19-2© Garland publishing
Overview of the cell cycle
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4based on Little Alberts 18-4© Garland publishing
”Checkpoints” in the cell cycle
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Cdk-cyclin complexes govern progression through the checkpoints(simplified view)
These proteins are regulated by 1. Kinase-mediated protein phosphorylation (lecture 14);2. Ubiquitin-mediated proteolysis (lecture 18).
Cdk is deactivated by
dephosphorylationwhen the cyclin is
destroyed
P
Cdk isitself activated by phosphorylation
a cyclin-dependent kinase (Cdk):
phosphorylates many proteins
a cyclin:required for kinase activity
based on Little Alberts 18-7© Garland publishing
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Cdk-cyclin complex is a “mitosis promoting factor” (MPF) also assayed by injecting into frog eggs
based on Little Alberts 18-6© Garland publishing
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Yeast uses the same Cdk at
both checkpoints;
mammals use different Cdks
at each checkpoint.
Little Alberts 18-13© Garland publishing
A yeast whose own Cdk is
mutated, and therefore
fails to divide, can be
rescued by expressing
human Cdk.
the cell cycle machinery
arose > 109 y ago !
Lectures 27, 28, 29 will
concern evolution.
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Some growth factors instruct cells to continue in the cell cycle
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abnormally active growth factor receptor
inactive growthfactor receptor
activated growthfactor receptor
abnormally active GPCR
But many molecules in this pathway can mutate to form oncogenes
onco-, cancer
based on Little Alberts 1st edition 18-23© Garland publishing
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A final stage, cell death, is also regulated by multiple mechanisms
Little Alberts 18-27© Garland publishing
dying nerve cells
Some autistic people have abnormally large brains. There is speculation about insufficient cell death.
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After Several Cell Cycle Divisions, most Cells Eventually Differentiate . . .
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. . . But Undifferentiated Cells Called “Stem Cells” Persist in some Adult Tissues
Embryo
AdultPersistent
Undifferentiated Cell
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Stem Cells can Both Differentiate
and Continue Cycling (Self-Renewal)
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Stem Cells can Generate Several Types of Differentiated Cells
D1 D2........ Dn
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As noted in slide 13, Stem Cells Exist in both Embryos and Adults
Embryonic Stem CellsEmbryonic Stem Cells
Adult Stem CellsAdult Stem Cells
Newly formed tissues and organs
Natural turnover Regeneration
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Isolating Stem Cells
Piece of Tissue
MultipotencySelf-renewal
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Stem Cells are Sometimes Purified Using Specific Cell Surface Markers
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Early example: a “Tissue-Specific” Stem Cell for the Blood and Immune System . . .
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. . . now we can work with Neural Stem Cells
Some types of gliaSome types of glia
NeuralTube
CNS
NeuronsNeurons
Peripheral neurons and related cells,
some muscles
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“Regenerative Medicine”: Stem Cells for Repair of Diseased or Injured Tissue?
•BloodBlood
•SkinSkin
•PancreasPancreas
•HeartHeart
•LiverLiver
•MuscleMuscle
•BrainBrain
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Cell Replacement Therapy for Neurodegenerative Disease?
Parkinson’s
Huntington’s
Alzheimer’s
Amyotrophic lateral sclerosis (ALS)
Spinal cord injury
Multiple sclerosis (MS)
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Theoretical example: Cell Transplant Therapy for Parkinson’s Disease
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Approaches to Stem Cell Therapies For Neurological Disease
1. Transplantation of neural stem cells
Donor: fetal brain
Advantages Disadvantages
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What Organism Should Supply the Stem Cells?
People
Animals
Lawyers
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True Embryonic Stem Cells Can Generate All Cell Types in the Body
Tissue-specific stem cells:
Germ-line
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1998: Human ES Cells
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Contribution of ES Cells to Internal Tissues in Chimeras
(Carrying a GFP reporter gene)
Chimeric embryo reveals ES-derived
GFP-expressing cells
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• Risk of graft vs. host disease; Immunosuppression needed
• Risk of graft vs. host disease; Immunosuppression needed
Material comes from IVF clinics;access to aborted fetal tissue notrequired
Material comes from IVF clinics;access to aborted fetal tissue notrequired
Advantages Disadvantages
Approaches to Stem Cell Therapies For Neurological Disease
2. Transplantation of ES cell-derived neural stem cells
3. Donor: blastocyst
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Cloning: 1960’s
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1997: Dolly, a Cloned Mammal
Success rate: 1/277. Dolly is now dead
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Step 1: The Egg’s Nucleus is Removed(= the Egg is Enucleated)
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Step 2: A Somatic Nucleus is Injected into the Enucleated Egg
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Step 3: The Injected Egg is Chemically Activated to Induce Nuclear Division
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Step 5: The Embryoid is Cultured Until a Blastocyst Develops
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Step 6: The Inner Cell Mass (A) is Removed from the Blastocyst and Cultured
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Step 7: Individual Human ES Colonies are Isolated
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-economics-economicsPending legislation to criminalize procedurePending legislation to criminalize procedure
““somatic cell nuclear transfer” akasomatic cell nuclear transfer” aka““therapeutic cloning”therapeutic cloning”
Advantages Disadvantages
Approaches to Stem Cell Therapies For Neurological Disease
3. Transplantation of ES cell-derived neural stem cells
Donor: nuclear transfer
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Some Unsolved Questions in Cloning and Stem Cell Research
• Why is producing ES cells by nuclear transplantation so inefficient?
• What events are involved in reprogramming a somatic cell nucleus to
regain pluripotency?
• How do we differentiate ES cells along particular lineages?
• How do we move from cell differentiation, to organogenesis?
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2004: California Takes the Lead with Prop 71
• Establishes the California Institute of Regenerative Medicine (CIRM)
• Allocates $3 billion over a 10-year period for stem cell research
• Provides funding for research with hES lines not fundable with federal
funds
– ie, all hES lines generated after 8/9/01
• Funding can be used for somatic cell nuclear transplantation
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Neurogenesis: new neurons are born in the adult rat and mouse brain. . . but we don’t know whether it happens in primate brain.
Gage, F.H. (2000) Science Gage, F.H. (2000) Science 287287:1433-1438:1433-1438
Hippocampus Olfactory Bulb
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Approaches to Stem Cell Therapies For Neurological Disease
4. Transplantation of adult brain cells
Donor: adult brain
Advantages Disadvantages
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Adult Stem Cell Plasticity: Bone Marrow-Derived Stem Cells for Brain
Would ProvideStem Cell Therapy without Transplantation
????
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• Not all brain regions may respond to the factors
• Not all brain regions may respond to the factors
Approaches to Stem Cell Therapies For Neurological Disease
5. In vivo mobilization of endogenous brain stem cells with growth factors
Advantages Disadvantages
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Bi 1 “Drugs and the Brain”
Lecture 24 Tuesday, May 23, 2006
Cell cycle, Stem Cells, and Stem Cell Therapy
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Adult Stem Cell Therapies for Neurological Disease?
• Adult neural stem cells
• Adult bone-marrow-derived stem cells
• In vivo mobilization
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Mouse ES Cells Differentiated into Motor Neurons
Wichterle et al. (2002) Wichterle et al. (2002) CellCell 110:385 110:385
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Does Any of This Have a Prayer of Working?
I SEE CELLS INYOUR BRAIN!
HOW LONG DOI HAVE TO WAIT?!
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We Need More Basic Research on Stem Cells
??