L7 - Ventralisation of the Neural Tube

Question 1

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

Answer 1

Neuroepithelium

Question 2

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

Answer 2

Becomes the DV axis

Question 3

Notochord is _______ to the neural tube

Answer 3

Ventral

Question 4

Skin ectoderm is _______ to the neural tube

Answer 4

Dorsal

Question 5

Neurones develop with ______________ throughout the entire DV axis

Answer 5

Bilateral symmetry

Question 6

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

Answer 6

Graft the notochord into an ectopic site

Question 7

What occured when the notochord was grafted into an ectopic location

Answer 7

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

Question 8

What is the Shh homologue in drosophila

Answer 8

Hh

Question 9

What does an insitu hybridisation against Shh show

Answer 9

That initially expressed in the notochord

Induced expression of Shh in the floor plate cells

Question 10

What does an antibody stain show about Shh expression

Answer 10

Forms a gradient - highest ventrally and lowest dorsally

Question 11

What does Shh confer

Answer 11

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

Question 12

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

Answer 12

Mimics the effect of the notochord and floor plate

Induces the secondary floor plate and ventral motor neurones

Question 13

What does Shh cause

Answer 13

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

Question 14

Where is the Shh gradient highest

Answer 14

Ventrally

Question 15

What occurs as the ventral cells differentiate

Answer 15

The move laterally and differentiate into a neurone

Question 16

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

Answer 16

Early stage DV

Question 17

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

Answer 17

The neural tube

Question 18

What does the mediallateral axis become

Answer 18

DV

Question 19

Where does the notochord form

Answer 19

On the ventral surface

Question 20

Whaere does the skin ectoderm form

Answer 20

On the dorsal surface

Question 21

What is the floor plate closest to?

Answer 21

The notochord

Question 22

The roof plate is ______ wherase the floor plate is ______

Answer 22

Dorsal

Ventral - next to the notochord

Question 23

What occurs at the same time as the neuralation

Answer 23

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

Question 24

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

Answer 24

Bilateral symmetry

Question 25

What is secreted by the notochord and the floor plate cells | What does this act as

Answer 25

Shh | Morphogen

Question 26

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

Answer 26

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

Question 27

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

Answer 27

Initially expressed in the notochord | This is then induced in the floor plate cells

Question 28

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

Answer 28

Antibody stain

Question 29

What does an antibody stain for Shh show

Answer 29

Forms a concentration gradient (highest ventrally - lowest dorsally)

Question 30

What does Shh cause

Answer 30

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

Question 31

What dose the TFs induced by Shh confer

Answer 31

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

Question 32

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

Answer 32

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

Question 33

In real life the set of TFs are readouts of the

Answer 33

Shh gradient

Question 34

Shh is highest

Answer 34

Ventrally

Question 35

What occurs to the cells as they differentitate

Answer 35

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

Question 36

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

Answer 36

Shh acts an early stage to confer a DV pattern

Question 37

What is the Shh gradient

Answer 37

Highest at the notochord and then the floor plate

Question 38

What is the BMP graient

Answer 38

From neural plate border cells and then the roof plate cells

Question 39

BMPs are members of the

Answer 39

TGF beta superfamily

Question 40

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

Answer 40

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

Question 41

Which way do cells move as they differentiate

Answer 41

Laterally

Question 42

Descibe how hedgehog signalling occurs

Answer 42

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

Question 43

Hh signalling creates a balance of

Answer 43

Gli activator and repressor

Question 44

What is the Hh signalling in the inactive form

Answer 44

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

Question 45

Describe the phenotype of the Shh -/-

Answer 45

``` Multiple dysmorphology No ventralisation of neural tube Holoprosencephaly Cyclopia Abnormal limbs/digits Lack of pituitary ```

Question 46

What is holoprosencephaly

Answer 46

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

Question 47

What does Shh govern

Answer 47

Governs ventralisation along the whole rosto-caudal axis

Question 48

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

Answer 48

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

Question 49

What type of neurones form in the forebrain

Answer 49

Hypothalamic neurones

Question 50

What type of neurones form in the midbrain

Answer 50

Dopaminegric neurones

Question 51

What type of neurones form in the hindbrain

Answer 51

Serotonergic neurones

Question 52

What neurones form elsewhere along the DV axis

Answer 52

Motor neurones