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CTO 2 > 7. Tissue repair > Flashcards

7. Tissue repair Flashcards

1
Q

How is the anterior - posterior axis positioned in central nervous system?

A
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2
Q

Which part of primary embryo brain develops into midbrain?

A

Mesencaphalon -> midbrain

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3
Q

What are the two main patterning structures of anterior-posterior axis of neural tube?

A
  • isO: isthmic organiser (FGF8)
  • nc: notochord (Shh)
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4
Q

How does dorso-ventral axis patterning occur in the neural tube?

A

Different signals secreted for patterning from:
- roof plate (rp)
- somites
- floor plate (fp)
—> different neurons protruced along dorso-ventral axis due to different signals

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5
Q

What neural cell subtypes and in which parts of the neural tube develop in dorso-ventral axis patterning?

A

Due to different signalling gradients in neural tube from roof plate / floor plate -> different neuron subtypes develop along dorso-ventral axis:
- dorsal root ganglion (drg)
- motor neurons (mn)
- spinal cord precursor

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6
Q

What are the main signalling molecules used for dorso-ventral axis formation in neural tube?

A
  • Shh (floor plate)
  • FGF8 (isthmic organiser)
  • Wnt (roof plate)
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7
Q

Explain what part of neural tube secretes Shh and what activates

A

Shh released from
- notochord
- floor plate

in neural tube -> activates GLI TF: Shh conc highest in ventral - highest GLI activaion in ventral side

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8
Q

How is Shh signal transmitted?

A

Signal transduction:
- Off state: Shh not bound to PTCH1 - inhibits SMO activity -> GLI- - GLI repressed -> GLI targeted genes not transcribed

  • On state: Shh binds to PTCH1 - binding activates SMO -> SMO activates GLI -> GLI targeted genes turned on by GLI TF
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9
Q

What is the gradient of Shh in neural tube?

A

Shh secreted by notochord and floor plate - highest Shh conc in ventral - lowest in dorsal axis => influences GLI TF activation - highest GLI activation in ventral - lowest in dorsal axis

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10
Q

What is the purpose of establishing Shh gradient in neural tube?

A

Different gradient -> different GLI TF activation -> different genes have different Shh thresholds for activation -> different neural cell identities developed

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11
Q

What is the mechanism behind negative feedback between two expressed genes for a single signalling molecule?

A

Complex gene expression patterns achieved by gene interaction:

Different genes have different signalling molecule thresholds for activation -> thresholds might overlap

Negative feedback:
when one threshold gene inhibits the overlaping gene expression

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12
Q

What are the anatomical parts of forebrain and hindbrain?

A

Forebrain: telencephalon, hypothalamus
Midbrain: -
Hindbrain: cerebellum

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13
Q

What is the pattern of Shh, Fgf8, Wnt expression in embryo?

A
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14
Q

What neurons induced by high Shh conc? What other signalling molecules contribute?

A

Dopaminergic (DA) neurons - form very close to neural floor plate
- Shh (high conc)
- Lmx1a
- Msx1/2
- Nurr1
Only midbrain tissue can form DA neurons

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15
Q

Can dorsal cells be induced to change to ventral cells?

A

Yes if Shh conc is increased:
dorsal cells -> ventral cells

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16
Q

Explain the function of isthmic organiser

A

isthmic organiser (isO) secretes FGF8 - important for dorso-ventral axis development in embryo

17
Q

What is an organiser?

A

Organiser - a group of cells that transmit a signal to adjacent cells to influence their developmental fate

18
Q

What Shh, Wnt, Fgf8 and their mixtures signal to develop?

A

Most important gradient - Wnt

19
Q

How does the brain anatomy change in case of Alzheimer’s, Huntington’s and Parkinson’s?

A

Alzheimer’s: brain mass shrinks
Huntington’s: brain mass shrinks
Parkinson’s: DA neurons degenerate (no visible change in mass)

20
Q

Where are DA neurones located?

A

Dopaminergic (DA) neurons in nigral midbrain (Substantia nigra)

21
Q

What is the function of DA neurons?

A

Dopaminergic (DA) neurons supply dopamine to putamen in striatum -> DA loss -> slow movement, tremmor

22
Q

What neural degeneration is involved in Parkinson’s?

A

DA neurons degenerate in Substantia nigra - no dopamine supply for putamen

23
Q

How can stem cell therapy be used to treat Parkinson’s?

A

DA neurons lost -> trying to recover DA neurons by injecting stem cells (fetal ventral midbrain tissue / hESCs / iPSCs) - into Substantia nigra - DA neurons recovered

24
Q

What happens if only one side of the brain exhibits DA neuron loss?

A
  • Parkinson’s induced in rats by injecting 6-OHDA -> assymetric motor deficit
  • when amphetamine given - hyperactive -> unilateral rotations (rotation direction depends on which side of the brain damaged)
25
Q

What are the problems associated with using fetal tissues in Parkinson’s treatment?

A
  • ethical issues
  • poor / unpredictable supply of tissue
  • poor quality / tissue heterogeneity
    => alternative - iPSCs
26
Q

What are the types of pluripotent stem cells?

A
  • embryonic stem cells (ESCs) - from IVF
  • induced pluripotent stem cells (iPSCs) - tissues taken from adults - pluripotency induced by TF
27
Q

How is DA neuron differentiation induced from stem cells?

A
  • ESCs / iPSCs differentiate into primary neural tissue
  • default path - forebrain cortical neurons
  • if Shh, Wnt, FGF8 introduced (floor plate signalling) -> DA neurons
28
Q

What tissue is the progenitor of DA neurons?

A

DA neuron progenitors - midbrain floor plate

29
Q

What is the process of making DA neurons from hESCs / iPSCs?

A

DA neurons from midbrain tissue - need to make midbrain:
1. SMAD inhibition -> anterior neural tissue
2. High Shh -> ventral side
3. ‘Tuned’ Wnt gradient -> caudal side
4. ‘Timed’ FGF8b -> midbrain

30
Q

What day of DA neuron development is best for transplant into Parkinson’s affected brain?

A

Day 16 - transplantable day

CTO 2 (8 decks)

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