Neural and PNS development 1, 2 and 3 Flashcards
1
Q
If neurons have their cell body in the spinal cord where are they generated from?
(1 mark)
A
Neural tube
2
Q
If neurons have their cell body elsewhere than the spinal cord where are they generated from?
(1 mark)
A
Neural crest
3
Q
What gives rise to the neural crest and how?
(3 marks)
A
Neural plate border:
- Neural tube folds and starts to close, neural plate border gets closer together and end at most dorsal part of neural tube
- Tubes closing cells delaminate and migrate away
4
Q
Where are the cell bodies of the PNS located?
(1 mark)
A
Dorsal root ganglion
and project to the spinal cord
5
Q
What kind of components can the neural crest make?
(7 marks)
A
- Neurons
- Smooth muscle
- Cartilage and bone
- Pigment cells
- Sesnory neurons
- Glia
- Adrenal cells
6
Q
What do cranial neural crest cells make?
A
Cartilage and bone
7
Q
What do trunk neural crest cells make?
A
Sympathetic neurons
8
Q
What neural crest cells are melanocytes made by?
A
ALL OF THEM xoxo
9
Q
How do you find out if all neural crest cells are multipotent stem cells?
(4 marks)
A
- Mark cell
- Figure out where it is ending and what its descendants are
- SO when it divides all daughter cells maintain that marker
- Means you can check if they are all DRGs, neurons and glia
10
Q
What is Cre-recombinase?
(1 mark)
A
Enzyme that recombines and stretches DNA that are located between 2 particular recognition sequences
11
Q
What is a LoxP site?
(2 marks)
A
- 34bp sequence made up of 2 13bp recognition sites, seperated by 8bp spacer region
- 13bp are recognised by Cre protein and form dimer
12
Q
What does Cre-recombinase do?
A
- Recognises LoxP sites and teh can switch DNA around depednig on orientation of sites and can recombinase what’s in the middle
13
Q
What is the process of getting confetti mice with Cre?
(3 marks)
A
- Put different fluorescent proteins between LoxP sites
- Can create different colours as different sites can be recombined with different frequency
- Lables different cells with different colours
14
Q
How does recombination with Cre and LoxP happen?
(2 marks)
A
- Target gene is floxed by inserting Lox sequence on either side of target gene - this line of mice is with the floxed gene then
- Gene is then crossed ith another transgenic mice carrying Cre recombinase which recognises LoxP and excises it out so offspring don’t have gene
15
Q
Are neural crest cells multipotent stem cells?
A
Yes
xoxo
16
Q
Does the cue for what a neural cell to produce come from its environment or is it intrinsic?
(2 marks)
A
- It does come from the environment
- If in a region where a specific kind of cell is meant to be produced it will switch from its original cell produced in old location to the one in the new environment
17
Q
What are cranial placodes?
(2 marks)
A
- Specialized regions of ectoderm that give rise to various sensory ganglia and contribute to the pituitary gland and sensory organs of the vertebrate head
- Local and transient thickening of the ectoderm in head and neck between prospective neural tube and epidermis
18
Q
What do cranial placodes do?
A
- Generate most of the peripheral neurons in head associated with smell, taste, hearing and balance
19
Q
What does the neural border do?
(2 Marks)
A
- Gives rise to the pre-placodal region only happens v anteriorly in head as a lack of Wnt signalling
- shows you need inhibition of Wnt to form the head
20
Q
Why is it necessary to limit the formation of the placodal field in the A-P domain and lateral domain?
A
- To form the epidermis in its place
- BMPs limit it laterally
- Wnt limits it anteriorly
21
Q
How does neural crest specification occur? (4 marks)
A
- Neural plate induction signals induce expression of neural crest border specifiers (TF)
- INduces neural crest specifiers (2nd set TF)
- Cell expressed will become neural crest which triggers them to undergo Epithelial Mesenchymal Transition and start migrating away
22
Q
What needs to happen to BMP in order to induce a neural fate?
A
Needs to be inhibited
23
Q
In a late gastrula, what signalling factors are needed to allow these components to form correctly:
(8 marks)
- Ectoderm
- Preplacodal field
- Spinal cord
- Neural crest
A
- Ectoderm - high BMP gives rise to epidermis
- Preplacodal field - low Wnt/ low BMP - express Otx2
- Spinal cord - high Wnt, low BMP
- Neural crest - high Wnt/ high BMP
24
Q
What markers are expressed in the:
a. ectoderm
b. preplacodal field
c. neural crest
(3 marks)
A
a. Ectoderm expresses keratins
b. Preplacodal expresses eya1 and Slv1
c. Neural crest expresses pax3 and Snail2, Max1/2
25
How do we know that BMP from ectoderm are inducing formation of cells at the very dorsal part of the spinal cord?
(4 marks)
* Because, if take cells from spinal cord that normally wouldn't become neural crest and culture with BMP will express **Pax6** and become spinal cord neurons
* Whereas, add ectoderm cells in cell culture will start expressing **neural crest markers** and same thing happens when add BMP4/7
26
What structures are involved in maintaining the structure of epithelial cells?
(3 marks)
* Epithelial cells form **monolayer**
* Connected to eachother by **adheren junctions**
* Have **basal lamina** that seperates them from underlying tissues
27
How does a mesenchymal cell form from an epithelial cell?
(3 marks)
* Epithelial cell **reorganises its additions and cytoskeletons**
* Not as tightly linked to neighbours as before
* **Breaks through basal lamina** and moves away and becomes **mesenchymal cell**
28
What does delamination mean?
Seperation of layers
29
During delamination of the neural crest, what do the neural tube and ectoderm express?
(2 marks)
* Ectoderm expresses **e-cadherin and BMP which induces Wnt signalling**
* Neural tube expresses **n-cadherin**
30
What are specialised cells to become the neural crest express in delamination?
* **Cadherin-6B**
31
Outline the process of delamination of neural crest cells.
(7 marks)
* BMP levels **highest in premigratory domain**
* Induce **Wnt signalling**
* Lead to expressino of core 'EMT regulatory factors: **Snail-2, Zeb-2, Foxd3 and Twist**
* Snail-2 **represses** expression of **E and N cadherin -** therefore neural crest cells DOWN REGULATE these - so not attatched to neural tube cells
* **Cadherin 6B activated** only in **apical ½ of pre-migratory cells** and activates **RhoA**
* Snail-2 **down regulates Cadherin 6B for delamination** - C6B exp in one region of neural crest cells to reorganise cytoskeleton
* After migration, neural crest cells **re-express cadherins**
32
What are the core EMT regulatory factors?
(4 marks)
* Snail-2
* Twist
* Zeb-2
* Foxd3
33
What genes are upregulated in neural crest cell delamination?
(4 marks)
* RhoB - cytoskeleton remodelling
* ItgB1 - attatchment to ECM
* Cad11 - cell:cell adhesion
* Cad7 - cell:cell adhesion
34
What genes are down regulated in neural crest cell delamination?
(3 marks)
* Ncad - cell:cell adhesion
* Ecad - cell:cell adhesion
* Cad6B - cell:cell adhesion
35
Where do trunk and cranial neural crest cells migrate?
(2 marks)
Trunk - **ventrally and laterally**
Cranial - **brachial arches**
36
What does the ventral segmental pathway give rise to?
(3 marks)
* Sensory and autonomic neurons
* Adrenomedullary cells
* Glial cells
37
Where does ventral migration happen?
* Anterior half of each **sclerotome**
38
What does the sclerotome give rise to?
Cartilage of the spine
39
What are somite and what do they give rise to?
(2 marks)
* **Balls of tissue** generated on both sides of the neural tube
* Give rise to **sclerotome and dermamyotome**
40
What is the difference between neural crest cells that are born in the anterior ½ of somite and those born in the posterior ½ of the somite?
Anterior ones are able to migrate and the posterior ones can't migrate
41
How does ephrin B1 cause neural cells to migrate around it?
(2 marks)
* in posterior ½ of sclerotome, ephrin B1 **repels NC cells**
* NC cells express **EphB3 on its surface** which interacts with EphB1 and transmits a **repulsive cue**
42
What are the external signals that guide trunk neural crest migration and how do they work?
(6 marks)
* **Laterally migrating cells** have a transcription which allows them to override repulsion of EphB1 (needed for them to migrate ventrally)
* Cadual part contains repulsive cues for NC cells - **Sema 3A/F, EphB1, Versican, F-Spondin**
* In anterior part, **Sdf1** produced where sympathetic ganglia form
* NC cells go to the rostral region where DRG are formed
* Sympathetic ganglia also formed ^^ - have receptor **CXCR4** which is **attracted to Sdf1** - cells move towards it
43
Explain the process of nerual crest cell migration by 'contact inhibition of local motion'.
(6 marks)
* 2 cells moving along and at some point they touch
* Contact triggers **rearrangement of cytoskeleton** and cells stop protruding into areas that their membranes are touching
* Start protruding ina reas **membranes are not touching and move away**
* Helps cells stay together
* Cells leading the way have space infront to make protrusions to advance
* Repulsive signals on the side
44
What proteins are secreted as cranial NC cells move by contact inhibition of locomotion?
* Low levels of N cadherin secrete **C3a proein**
45
What are the 3 major migratory streams?
| (6 marks)
1. **NC in hindbrain and r1 and r2** - migrate 1st pharyngeal arch
2. **NC cells of r4** - migrate to 2nd oharyngeal arch
3. **NC cells of r6-r8** - migrate to 3rd and 4th pharyngeal arches
46
What are the signals guiding neural crest migration shown in r3?
(3 marks)
* r3 expresses **Sema3f**
* Cells that express the receptor for Sema3f are then **repelled**
* NC cells express receptors which encounter proteins that are repulsive
47
What proten is expressed in placodal cells?
(2 marks)
**VEGF**
- expressed to attract NC cells to move to together - NC cells only ones to encounter placodal cells
48
What is the 'chase and run' model?
| (3 marks)
* Placode cells infront og NC cells and secrete SDF1 (chemoattractant)
* NC cells like SDF1 an move towards them when they touch it triggers **CIL**
* But since attractant is being secreted by neural cell it goes back anyway
