LEC 31

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  1. What is the area identity?
    Brain is separated into many domains
  2. Intrinsic
    Cell decides what it’s going to do to drive cell fate
  3. Extrinsic
    • Cell isn’t completely isolated
    • Responds to external factors
  4. How is the V1/V2 layer distinguishable?
    By the cytoarchitecture
  5. Where do the extra cell layers start to form in the V1 cortex?
    Cell layers start to form at 4th layer
  6. Name the cortices in the brain from anterior to posterior.
    • Motor cortex
    • Somatosensory cortex
    • Auditory cortex
    • Visual cortex
  7. Name the cortices in the brain from posterior to anterior.
    • Visual cortex
    • Auditory cortex
    • Somatosensory cortex
    • Motor cortex
  8. What kind of input do distinct ares of neocortex receive?
    Different thalamocortical axon (TCA) inputs
  9. What does TCA stand for?
    Thalamocortical axon
  10. How are the identities of neocortex areas determined/specified?
    Independently of axonal input from TCA
  11. How do all signals, besides olfactory, reach the cortex?
    By relay of the thalamus (TCA)
  12. Which sensory signals reach the cortex by relay of the thalamus?
    All but olfactory
  13. What are the two transcription factors expressed in the developing cortex in mice?
    Emx2 and Pax6
  14. What are Pax6 and Emx2?
    • Transcription factors that help drive AP cell fates when expressed
    • Intrinsic factors
    • (but external signals exist too)
  15. How are the transcription factors expressed in the cortex of mice?
    In gradients
  16. What can you say if you see one gradient?
    Chances are there is an opposing gradient
  17. How are Emx2 and Pax6 expressed?
    In opposite rostral-caudal gradients
  18. What do Emx2 and Pax6 do?
    Help dictate regional specificity
  19. Where is pax6 expressed most? Least?
    • Most- Anteriorly (rostrally)
    • Least- Posteriorly (caudally)
  20. Where is emx2 expressed most? Least?
    • Most- Posteriorly (caudally)
    • Least- Anteriorly (rostrally)
  21. What happens when there’s a mutation in pax6?
    • Causes posteriorization (expansion of the posterior)
    • Boundary of posterior marker shifts anteriorly
  22. What happens when there’s a mutation in emx2?
    • Causes anteriorization (expansion of the anterior)
    • Boundary of anterior marker shifts posteriorly
  23. What is the hypothesis of the roles of Emx2 and Pax6?
    They play a role in establishing areal cell fates along the AP axis
  24. What is FGF?
    • Fibroblast growth factor
    • Influences areal patterning
  25. How is FGF expressed in the cortex?
    • In a gradient
    • High anterior, low posterior
  26. What happens when ectopic FGF8 is expressed in the anterior of the cortex?
    • Causes posterior shift of cortical domains
    • Anteriorization
  27. What happens to the somatosensory cortex when FGF is expressed caudally? Give an example.
    • Cells think they're close to the cell anteriorly
    • Adopt new/different cell fate; duplicated S1 cortex
    • Duplication of mouse whisker barrel field
  28. What is the path of sensory signals when mouse whiskers bend?
    • Trigeminal nucleus
    • Brain stem
    • Dorsal thalamus (VP)
    • Neocortex
  29. What are all the factors that work together to pattern the motor sensory areas?
    • Anterior and posterior fgf8 gradient
    • Intrinsic transcription factor gradients for Emx2 and Pax6
  30. What was the first experiment that showed that afferent/extrinsic input from thalamus also influences organization of sensory cortex?
    • Transplanted visual cortex tissue of mouse into somatosensory cortex
    • Wait for it to mature
    • See that whisker barrel fields form visual cortex (sensory signals now help vision?)
    • Even though there's intrinsic patterning in cortex, there's enough plasticity that allows remodeling
  31. What was the second experiment that showed that afferent/extrinsic input from thalamus also influences organization of sensory cortex?
    • Compared how different inputs from other auditory and visual cortex could affect patterning of developing cortex
    • Removed inferior colliculus
    • No signal to MGN (medial geniculate nucleus) from cochlea
    • RGC from retina innervated both LGN and branched to innervate MGN
    • What used to be auditory cortex now responds to visual cues
  32. What are the two principle neuronal types?
    Excitatory (glutamatergic) and inhibitory (GABAergic) neurons
  33. Where do excitatory neurons come from?
    • Progenitors in the dorsal cortical ventricular zone
    • Migrate radially to occupy the future vesicular cortex
  34. What controls the excitatory neurons?
    Neurogenin 1 and 2
  35. Where do inhibitory neurons come from?
    • Progenitors in the ventral ganglionic eminences
    • Migrate dorsally to become interneurons
  36. What controls the inhibitory cells?
    Mash1
  37. What are neurogenin 1-2 and mash1?
    Basic helix-loop-helix (bHLH) transcription factors that dictate the nt phenotypes that cells release
  38. How many principle layers are there in the audlt cortex?
    6
  39. Which two layers are grouped together for simplicity's sake b/c they're hard to distinguish?
    Layer 2/3
  40. What kind of cells do the 6 cortical layers consist of?
    Excitatory pyramidal neurons w/ different roles
  41. What are the 5 layers/areas where cells migrate and develop from top to bottom?
    • Marginal zone
    • Cortical plate
    • Subplate
    • Intermediate zone
    • Ventricular zone
  42. Where do cortex layers 2-6 form?
    In the developing cortical plate
  43. What's another name for the progenitor cells starting in the ventricular zone?
    Radial glia
  44. Where are the dividing progenitor cells located?
    Ventricular zone
  45. What are radial glia cells?
    Progenitor cells
  46. Where are radial glia cells located?
    • Extends from the ventricular zone to the marginal zone
    • Entire length of the early cortex
  47. What happens in the intermediate zone?
    Post mitotic cells migrate upward
  48. How do post mitotic cells migrate up to the cortical plate?
    Along the scaffold of radial glia
  49. Where does differentiation of post-mitotic cells finish?
    At the cortical plate
  50. When is a cell considered "born"?
    When the cell last divides
  51. How do progenitor cells divide?
    Symmetrically or asymmetrically
  52. What influences the fates of dividing progenitor cells?
    The plane of division with respect to the epithelial surface of the ventricular zone
  53. What happens during asymmetric division?
    Progenitor will give rise to a progenitor cell, and a neuronal precursor which will migrate on radial glia into the cortical plate (future cortex)
  54. When does asymmetric division occur?
    When mitotic spindle lines up perpendicular to the epithelial surface of the ventricular zone
  55. How does asymmetric division occur?
    Cell divides upon the cleavage plane, that’s parallel to the epithelial surface
  56. What happens during symmetric division?
    Progenitor gives rise to two new progenitor cells
  57. When does symmetric division occur?
    When the mitotic spindle lines up parallel to the epithelial surface of the ventricular zone
  58. How does symmetric division occur?
    Cells divide upon the cleavage plane, that’s perpendicular to the epithelial surface
  59. Why does the orientation of the cell's cleavage plane matter with division?
    • Some cell-fate determining proteins can be unevenly distributed during mitosis
    • Depending on how cells divide, one cell may get all or none of that protein
    • Could lead to cell-fate decision like becoming neuron
  60. What are examples of cell-fate determining proteins?
    Notch and numb (which inhibits notch)
Author:
Mursizzle
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313219
Card Set:
LEC 31
Updated:
2015-12-14 15:22:07
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lecture neuro 31
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