1 bi 1 “drugs and the brain” lecture 24 tuesday, may 23, 2006 cell cycle, stem cells, and stem...

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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

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

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

• 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

-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

????

• 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

??