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BMS249 Dev Neurobiology > L7 - Ventralisation of the Neural Tube > Flashcards

L7 - Ventralisation of the Neural Tube Flashcards

1
Q

What is the single cell thick neural plate also referred to as

A

Neuroepithelium

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2
Q

When the neural tube forms what occurs to the medial lateral axis

A

Becomes the DV axis

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3
Q

Notochord is _______ to the neural tube

A

Ventral

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4
Q

Skin ectoderm is _______ to the neural tube

A

Dorsal

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5
Q

Neurones develop with ______________ throughout the entire DV axis

A

Bilateral symmetry

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6
Q

How can it be tested that the notochord acts as a DV axis organiser

A

Graft the notochord into an ectopic site

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7
Q

What occured when the notochord was grafted into an ectopic location

A

Induction of a secondary floor plate with bilateral symmetry of secondary motor neurones

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8
Q

What is the Shh homologue in drosophila

A

Hh

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9
Q

What does an insitu hybridisation against Shh show

A

That initially expressed in the notochord

Induced expression of Shh in the floor plate cells

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10
Q

What does an antibody stain show about Shh expression

A

Forms a gradient - highest ventrally and lowest dorsally

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11
Q

What does Shh confer

A

Ventral neural tube identities so progenitors will ultimately give rise to cells that differentiate into ventral motor neurones

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12
Q

What occurs when a bead soaked in Shh is grafted into an ectopic site

A

Mimics the effect of the notochord and floor plate

Induces the secondary floor plate and ventral motor neurones

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13
Q

What does Shh cause

A

Set of transcription factors which are a read outs of the Shh gradient

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14
Q

Where is the Shh gradient highest

A

Ventrally

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15
Q

What occurs as the ventral cells differentiate

A

The move laterally and differentiate into a neurone

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16
Q

Shh acts at an ___________ to confer a _______ pattern of TFs on progenitor cells

A

Early stage DV

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17
Q

Oncee the single cell neuroepithelium has been formed what is then induced

A

The neural tube

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18
Q

What does the mediallateral axis become

A

DV

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19
Q

Where does the notochord form

A

On the ventral surface

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20
Q

Whaere does the skin ectoderm form

A

On the dorsal surface

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21
Q

What is the floor plate closest to?

A

The notochord

22
Q

The roof plate is ______ wherase the floor plate is ______

A

Dorsal

Ventral - next to the notochord

23
Q

What occurs at the same time as the neuralation

A

The axial mesoderm (notochord and prechordal mesoderm) forms and comes just beneath the ventral midline of the neural tube

24
Q

What do neurones develop with around the midline throughout the whole DV axis

A

Bilateral symmetry

25
Q

What is secreted by the notochord and the floor plate cells

What does this act as

A

Shh

Morphogen

26
Q

How can it be tested that the notochord and floorplate secrete a morphogen
What were the results of this experiement?

A

Grafting the notochord into an ectopic site into a host embryo
Induces a secondary floor plate and second set of motor neurones around - these exhibit bilateral symmetry

27
Q

What does an in-situ hybiridisation over time for Shh show

A

Initially expressed in the notochord

This is then induced in the floor plate cells

28
Q

What experiment could be used to show that Shh is acting as a morphogen

A

Antibody stain

29
Q

What does an antibody stain for Shh show

A

Forms a concentration gradient (highest ventrally - lowest dorsally)

30
Q

What does Shh cause

A

Expression of a certain set of TFs in the cells that it act on

31
Q

What dose the TFs induced by Shh confer

A

Ventral neural tube identities so progenitors will give rise to cells that differentiate into ventral neurons

32
Q

What is the experimental evidence that it is SHH as a signalling molecule

A

Bead soaked in purified Shh protein is able to mimic the effect of the notochord and floor plate - induces a secondary floor plate and motor neurones

33
Q

In real life the set of TFs are readouts of the

A

Shh gradient

34
Q

Shh is highest

A

Ventrally

35
Q

What occurs to the cells as they differentitate

A

As they divide one cell retained as the mother cell and one moves laterally and differentiates into a neurone

36
Q

Shh acts at an __________ to confer ________ of TF on progenitor cells

A

Shh acts an early stage to confer a DV pattern

37
Q

What is the Shh gradient

A

Highest at the notochord and then the floor plate

38
Q

What is the BMP graient

A

From neural plate border cells and then the roof plate cells

39
Q

BMPs are members of the

A

TGF beta superfamily

40
Q

Progenitor domains made up of bands of proliferating cells are established by …

A

The opposing action of BMPS/WNTS (dorsally) and Shh (ventrally)

41
Q

Which way do cells move as they differentiate

A

Laterally

42
Q

Descibe how hedgehog signalling occurs

A

Hh ligand binds to Ptc
Ptc then unable to inhibit Smo
Smo then causes an increase in the ammount of Gli activator

43
Q

Hh signalling creates a balance of

A

Gli activator and repressor

44
Q

What is the Hh signalling in the inactive form

A

No Hh ligand bound to Ptc
Normal function of Ptc is to inhibit Smo
Smo unable to cause increase in Gli activator
Smo unable to cause increase in Gli activator ]
More gli repressor than gli activators

45
Q

Describe the phenotype of the Shh -/-

A 
Multiple dysmorphology 
No ventralisation of neural tube 
Holoprosencephaly 
Cyclopia
Abnormal limbs/digits 
Lack of pituitary
46
Q

What is holoprosencephaly

A

Where there is no separation of the two parts of the brain

47
Q

What does Shh govern

A

Governs ventralisation along the whole rosto-caudal axis

48
Q

How come different neurones are formed at different levels along the A-P axis of the neural tube

A

The DV shh gradient intersects the AP hox gradient - forms a Cartesian grid of information - leads to different types of neurones being formed that are in the same DV position but differ on the AP axis

49
Q

What type of neurones form in the forebrain

A

Hypothalamic neurones

50
Q

What type of neurones form in the midbrain

A

Dopaminegric neurones

51
Q

What type of neurones form in the hindbrain

A

Serotonergic neurones

52
Q

What neurones form elsewhere along the DV axis

A

Motor neurones

BMS249 Dev Neurobiology (16 decks)

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