lecture27_s05 by niusheng11

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									Lecture 27
Stem Cells
Study Guide
1. Know the different kinds of stem cells and their characteristics
2. Compare and contrast the two techniques for measuring neurogenesis
3. Identify two areas in the adult brain that support neurogenesis.
   Describe neurogenesis in these two areas.
                                  Stem Cells

Fertilized egg
         totipotent stem cell
         self-renewing
         give rise to all cells

Embryonic stem cells (ES) – derived from pre-gastrula
      self-renewing
      give rise to most tissue and cell types through organism
              (pluripotent)

Somatic stem cells – committed stem cell
      broad class of stem cells
      self-renewing
      differentiate into full range of cell classes within a tissue
                    Neural Stem Cells

Neural stem cells
       somatic stem cells
       self-renewing
       differentiate into main cell classes found in CNS and PNS
               (neurons and glia)

Neuroblasts
      non-dividing cells that develop into neurons

Differentiated neuron
        cannot divide
Embryonic Stem Cells

 From a Blastocyte
Gastrulation
Neurulation
Neurogenesis from Neural Stem Cells in Neural Tube
Cloned Neuronal Stem Cells




               A. Neurosphere: from adult forebrain
               i.. GABAergic neurons
               ii. Astrocytes
               iii. Oligodendrocytes
Induction of Neurons from Stem Cells


              Pretreatment of embryonic stem cells with
              retinoic acid:

                      differentiate into mature motor
                      neurons when introduced into embryo

              Middle – cells extending axons

              Bottom – motor neuron-like morphology
Activation of neuronal development by retinoic acid




 Retinoic acid is inductive signal for neuron differentiation

 Left – blue areas indicate gene activation
 Right – retinoic acid increases gene activation
Retinoic Acid as a nervous system teratogen




Teratogen – birth defects induced by exogenous agents

Left – normal brain
Right – Retinoic acid delivered at mid-gestation as Accutane drug to
treat severe acne
   Neuronal Stem Cells in the Adult Brain

History

1950’s: 3H-thymidine incorporation of DNA into dividing cells
   autoradiography

1960’s: 3H-thymidine method applied to adult brain showing neurogenesis
         in neocortex, dentate gyrus and olfactory bulb (Joseph
         Altman)
         ignored for two decades as an artifact (difficult to distinguish
         developing neuron from glia)

1980’s: Fernando Nottebohm (Rockefeller University)
   adult song birds make new neurons in brain region associated with song
         process accelerates during season birds acquire songs
   process accelerates during season when memory is very important to
         remember dispersed food storage sites
   canary makes 20,000 neurons per day

1984: Pasko Rakic: leading researcher on primate brain development found no
        3H-thymidine accumulation in monkey brain
   Neuronal Stem Cells in the Adult Brain
History

1990’s: BrdU (5-bromo-3’-deoxyuridine)
        like thymidine, taken up by cells during S-phase of mitosis
        visualized by immunocytochemistry (combine with other cell markers

New evidence for neurogenesis in adult nonhuman, primate brain by
  Elizabeth Gould and Bruce McEwen (Rockefeller) and Eberhard Fuchs
        (German Primate Center)
  1997, neurogenesis in hippocampus of primate-like tree shrew
  1998, neurogenesis in marmoset, distant primate relative of human
  1998, Gould and Rakic found neurogenesis in hippocampus of rhesus
        monkeys
  1999, Princeton researches found neurogenesis in cerebral cortex

Evidence for neurogenesis in adult human
   BrdU used in cancer patients (tongue or larynx) to monitor growth
   1998, Fred Gage (Salk Institute) and Peter Eriksson (Sweden) examined
        brains on autopsy
   found neurogenesis in hippocampus
   patients aged from 57 to 72
Labeling Neurogenesis




  a.   3H – thymidine in rat
  b.   BrdU in rat
  c.   BrdU in mitotic anaphase
  d.   BrdU in dying (pyknotic) cell
Labeling Neurogenesis and Cell Markers




   a.   BrdU (red) and oligodendrocyte marker (CNP, green)
   b.   BrdU (red) and neuronal marker (MAP-2, green)
   c.   BrdU (red) and neuronal marker (TuJ1, green)
   d.   BrdU (red) and retrograde tracer to mark cell body (Blue)
   e.   BrdU (red) and neuronal marker (NeuN, green)
          Neurogenesis in the Olfactory Bulb




Stem cells found in anterior subventricular zone (epithelial lining of ventricles)
Postmitotic neuroblasts migrate to olfactory bulb through rostral migratory stream
      Neurogenesis in the hippocampus




Stem cells in basal aspect of granule cell layer in dentate gyrus
Postmitotic neuroblasts translocate to granule cell layer in apical levels
Control of Neurogenesis


   Stress

   Exercise

   Intellectual Activity

   i.e., live right!!!!

								
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