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

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


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Cdk-cyclin complex is a “mitosis promoting factor” (MPF) also assayed by injecting into frog eggs


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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



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”



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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4. Transplantation of adult brain cells

Donor: adult brain


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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


5. In vivo mobilization of endogenous brain stem cells with growth factors


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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

??

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

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