Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BMS 249 - Developmental Neurobiology > Ventralisation of the neural tube > Flashcards

Ventralisation of the neural tube Flashcards

1
Q

What is neurulation?

A

Formation of the neural tube, from the rolling up of the neuroectoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What transforms the medio-lateral axis into the dorso-ventral axis?

A

Neurulation - when the neuroectoderm rolls up to form the neural tube

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where does the notochord lie?

A

Underneath the neural plate and then comes to lie underneath the ventral midline of the neural tube

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the ventral floor plate?

A

A group of specialised glial cells which lie at the midline of the ventral neural tube, above the notochord

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How do neurons develop around the neural tube?

A

With bilateral symmetry, through the entire DV axis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What determines the cell type of cells near the floor plate

A
  • Morphogen gradient from the floorplate and notochord

- Different cell types dependant on what concentration of the morphogen they see

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How was is shown that a secreted signal came from the notochord and floor plate and induced cell type?

A
  • Graft a donor notochord into an ectopic position
  • Ectopic floor plate and ventral neurons with bilateral symmetry
  • Showed that secreted signals from the notochord causes the cells in the neural tube to adopt a different fate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the secreted factor from the notochord and floor plate?

A

Shh

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is special about Shh?

A

Conserved through evolution

Has homologue in drosophila

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where was Hh discovered and how?

A

Discovered in drosophila

Mutations in this gene causes the fly to curl up and look spiky (like a hedgehog)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How was it proved that Shh is a secreted molecule? (2 ways)

A
  • Look at the DNA sequence (contains information about what the protein is destined to do)
  • Apply antibodies (show protein decorates cells distant to the ones making it in the floorplate/notochord)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What induces Shh expression in the floor plate?

A

Shh release from the notochord

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What does Shh do?

A
  • Diffuses away from the floorplate and notochord
  • Setting up a concentration gradient (high concentration ventrally, low concentration dorsally)
  • Turns on Shh signalling in neighbouring cells, which up-regulate ventral transcription factors, dependant on the concentration of Shh which they see
  • These progenitor cells then ultimately develop into ventral neurons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How was it shown that is was infact Shh coming from the notochord that induced ventral fates and not something else?

A
  • Shh soaked bead produced ectopic floor plate and motor neurons with bilateral symmetry around the midline (along the DV axis)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What do the transcription factors expressed by the progenitors code?

A

Later differentiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What do the progenitors give rise to?

A

1) A daughter cell which remains in the same place as the mother
- Progenitor (neuronal stem cell)

2) A daughter which migrates away laterally to the mantle zone and differentiates into a neuron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What TF are expressed in the daughter cell of a progenitor, which remains at the ventricular zone?

A

Expresses the same pattern of TFs as the mother

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What happens to the daughter cell which moves away from the VZ?

A

Differentiates into a neuron - change in the TFs expressed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

When does ventralisation and dorsallisation of the neural tube occur?

A

At the same time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How do Shh and BMP act with eachother?

A

They act antagonistically - repressing each other at the level of transcription factors and at protein level, to set up bilateral stripes of different neuronal classes along the D-V axis, all with different identities

21
Q

What neuronal fates do BMPs set?

start from closest to roof plate

A

Dorsal 1 INTERNEURONS
Dorsal 2 INTERNEURONS
Dorsal 3 INTERNEURONS

22
Q

What neuronal fates does the Shh gradient set?

start from closest to floor plate

A

Ventral 3 NERUONS
MOTOR NEURONS
Ventral 2 INTERNEURONS
Ventral 1 INTERNEURONS

23
Q

When does expression of Shh occur?

A

After the expression of BMPs and neurulation

24
Q

Where do sensory neurons come into the neural tube?

A

At the top

25
Q

How are sensory neurons born?

A

From migratory neural crest cells which have coalesces to form sensory ganglia (DRG)

26
Q

Where do relay interneurons lie?

A

Between the dorsal and motor pools

27
Q

When are relay interneurons born?

A

Under the influence of either BMP signalling or low Shh signalling

28
Q

Where are motor neurons born and how?

A

Ventrally, in response to high levels of Shh signalling

29
Q

What happens to neurons once they have acquired their fate and position?

A

They differentiate further by extending their axons

30
Q

Where to motor neurons project?

A

To the periphery

31
Q

Where do interneurons project?

A

Within the spinal cord ventrally

32
Q

What are Ptc and Smo?

A

Transmembrane receptors

33
Q

What happens in the cell when Hh signalling is not active?

A
  • Ptc represses Smo
  • Intracellular end of Smo cannot interact with downstream machinery
  • Majority of Gli TF is in its repressive form
  • Gli R represses Hh target genes from being transcribed, by sitting on the promoter of the gene
34
Q

What is Gli?

What does it do?

A

A transcription factor which has 2 forms:

  • Repressive
  • Active

Both forms act non-autonomously to determine the progenitor identify and neuronal fate

35
Q

What happens in the cell when Hh signalling is active?

A
  • Hh binds to Ptc - preventing the inactivation of Smo
  • Intracellular end of Smo shifts Gli in favour of Gli A
  • Gli A binds to the promoter of the gene and allows Hh target genes to be transcribed
36
Q

Why do we want to know the transcription profile of cells that are influenced by Shh?

A
  • If know how much Shh a cell needs to turn a particular set of TFs which define a motor neuron progenitor
  • Can take pluripotent cells and expose them to exactly the right amount of Shh, to get a motor neuron

(Beneficial for diseases like motor neuron disease)

37
Q

Where is Shh expressed in the body?

A

Along the entire A-P axis

Always ventral in position

38
Q

Where also expresses Shh in the forebrain?

A

Special set of cells above the prechordal mesoderm

39
Q

What happens when Shh is knocked out in the mouse?

A
  • Get 3 germ layers, neural plate, neural tube and dorsally patterning as normal (shh not needed in these steps)
  • BUT, get no ventralisation of the neural tube
40
Q

What are the symptoms in a mouse with no Shh?

A

1) Holoprosencephaly
- Faliure of the forebrain to form
- No bilateral symmetry of the brain into 2 parts

2) Cyclopia
3) Abnormaly limbs/digits

4) Lack of pituitary
- Abnormal growth and appetite

41
Q

Why is there lack of pituitary in mice with Shh knockout?

A
  • Midline of the forebrain is the hypothalamus, which sets up the pituitary
  • Forebrain doesn’t form
42
Q

What do patients with holoprocencephaly or cyclopia have an abnormality in

A

Shh or the Shh pathway

43
Q

What does the notochord become at the rostral end and what does this induce?

A
  • The prechordal mesoderm (PRECHORDAL PLATE)

- Induces Shh expression in the overlying forebrain cells

44
Q

Why are there different types of neurons at the same D-V position along the A-P axis, even though Shh governs ventralisation along the entire AP axis and is at the same concentration in the notochord?

A
  • There is an earlier established A-P patterning of the neural tube (Hox code)
  • Forms a Cartesion grid of information, along with the patterning information in the D-V axis

(see different Hox genes, along with different concentrations of Shh morphogen)

  • Cells respond by changing fate, depending upon there position in the grid and what TFs the cell sees
45
Q

How is Shh detected better, with antibodies or mRNA?

A

With antibodies

46
Q

How do Gli R and Gli A interact?

A

They both bind to the promoter of the gene

Gli R masks the activation site from Gli A when no Hh is present

47
Q

What do neurons do as they migrate laterally?

A

Differentiate into neurons which are ‘preprogrammed’ by the subset of transcription factors which they express

48
Q

In patterning of the DV axis of the neural tube, what is Shh/BMP/Wnt signalling converted to?

A

A GliR- GliA gradient

BMS 249 - Developmental Neurobiology (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions