L3/4 - Neural plate formation + neural induction Flashcards
(73 cards)
1
Q
What aspects of NS formation is common to both vertebrates and invertebrates
A
Neurogenic region found next to the skin
This migrates down then goes inside
2
Q
What feature of NS formation is found only n invertebrates
A
Delamination forming the neruoblast cells
3
Q
What feature of NS formation is found only in vertebrates
A
Inc cell cell adhestion contact
Either side the neural plate is bound by ectoderm, this then fuses above the neural plate
4
Q
What would happen if all of the cells took their default state
A
All would become skin
5
Q
Define differentiation
A
Process by which cells are able to become different and acquire specialised properties
6
Q
What is cell differentiation governed by
A
Changes in gene expression which influences the repertoire of proteins expressed in a cell
7
Q
Over time what happens to specialisation and pluripotency
A
Spec inc
P.P dec
8
Q
Is BMP found is vertebrates of invertebrates
Give an example of an organism it is found in
A
Vertebrtes
Xenopus
9
Q
Is Dpp found in vertebrates or invertebrates
Give an example of an organism it is found in
A
Invertebrates
Drosophila
10
Q
BMP7 homologue in drosophila
A
Screw
11
Q
What does BMP stand for
A
Bone morphogenic protein
12
Q
What does dpp stand for
A
Decapentaplegic
13
Q
BMP1 homologue is drosophila
A
Tolloid
14
Q
BMP4 homologue is drosophila
A
Dpp
15
Q
Chordin homologue is drosophila
A
Short gastrulation (SOG)
16
Q
Screw homologue in xenopus
A
BMP7
17
Q
Dpp homologue in xenopus
A
BMP4
18
Q
Tolloid homologue in xenopus
A
BMP1
19
Q
SOG homologue in xenopus
A
Chordin
20
Q
Normal function of Chordin/SOG
A
Inhibition of BMP/dpp signalling
21
Q
What is the normal function of BMP4 and dpp
A
The activation of non-neural homeobox genes
22
Q
Describe the BMP signalling when BMP has bound to the receptor
A
Phosphorylation of the receptor Phosphorylation of R-SMAD Combines with SMAD4 Enters the nucelus via the nuclear pore Trancriptional complex Dephosphorylation and it leaves the nucleus
23
Q
What are the 3(4) components of the SMAD transcriptional complex
A
PHOSPHORYLATED R-SMAD
SMAD4
Co factor
24
Q
What two antagonists inhibit BMP signalling
A
Noggin and chordin
25
What is the function of noggin
Causes the inactivation of SMAD4
26
What are BMP and chordin examples of
Genes that have been conserved throughout evolution
27
What are the two mechanisms by which chordin and sog act as antagonists of the BMP/dpp signalling pathwat
Act as a sponge moping up dpp/bmp (binding to and inactivating)
Competitively bind at receptors preventing binding of dpp/bmp
28
What does Dpp and SOG broadly dictate
The dorsal and ventral axis
29
What genes are expressed on the dorsal side of the embryo (insect)
Dpp, tld, tsg and SV-2
30
Describe the activity of the dpp pathway on the dorsal side of the embryo (insect)
No inhibition of the dpp pathway
31
What cell fate is taken by cells on the dorsal side of the embryo (insect)
Epidermal
32
What genes are expressed on the ventral side of the insect embryo
Sog and screw
33
What is the action of SOG
Inhibition of dpp binding to its receptor
34
What fate is taken by cells on the ventral side of the cell
Neural cell fate - neurogenic region is formed
35
What side is the NS found in insects
Ventral
36
What side is the NS found in vertebrates
Dorsal
37
Why is there a difference between the sides which the NS is found in vertebrates and invertebrates
Possibly due to a rotation of the head
38
Genes expressed at the dorsal end of a vertebrate - what fate do these cells then take
Chordin and Admp cells take a nerual cell fate
39
Genes expressed at the ventral end of an invertebrate
| What fate do these cells take
Sog, Screw
40
Molecular pathway
| ECTODERM IN PRESSENCE OF BMP SIGNALLING
High SMAD1 and low SMAD1
Msx1, GATA1, Vent (epidermalising transcription factors)
LEF1
Epidermal differentiation
41
Molecular pathway
| ECTODERM WITHOUT BMP SIGNALLING
```
Low SMAD1 and high SMAD7
Xlpou2, SOXd/B (neuralising transcription factors)
Neurogenin
NeuroD
Neural differentiation
```
42
What process results in the formation of the neural tub
Neuralation
| Neural plate rolls up to form the neural tube
43
What occurs during spinobifia
Failure of the neural tube to close properly
44
What can reduce the chances of spinobifida occuring
Folic acid
45
How do we know there are 3 germ layers found in the embryo
Repitore of proteins expressed - use of an antibody stain
| mRNA being expressed - look at using an in-situ hybridisation
46
What sets up the polarity of the early embryo
Established early on due to gravity and interaction of the placenta (in mammals) different cytoplasmic determinants have sunk to the one part of the egg. Leads to cells of this region becomming different and having a specific set of factors being activated
47
Which part of the embryo is fated to become the furture CNS
Cells immediatly adjacent to the organiser
48
What signal does the organiser secrete ... what does this lead to
GSC is expressed this acts to upregulate Chordin , Noggin and Follistatin
These secreted molecules act to inhibit BMP signalling
49
What the result of BMP signalling inhibiton
Neural plate induction
50
What are some antagonists of the BMP signalling pathways
Chordin
Noggin
Follistatin
51
Outline the stages of mesoderm induction and patterning
Low level Nodal gives the ventral mesoderm
High level Nodal gives the organiser
Signals from the organiser acts to inhibit BMPs to dorsalise and pattern adjacent mesoderm
Antagonism of BMPs --> Gives a neral identity
52
What receptors do BMPs bind to
TGFb-R
53
How to BMPs tend to act
Locally and diffuse to neigbouring cells
54
What fate do cells take if BMP signalling is active
Cells take an ectodermal cell fate
55
How do chordin noggin and follistatin act as inhibitors of the BMP signalling pathway
Antagonists compete for BMP binding - no longer able to activate receptors and cause activation of the BMP pathway
56
What is different in the development of chicks and humans
flattened into three sheets not a hollow sphere
57
What do cells in the organiser differentiate into
Axail mesendoderm and anteiror endoderm
58
What makes up the axial mesendoderm
Anteior endoderm, precordal mesoderm, notochord
59
What then happens to the axial mesendoderm
Involute, intercalates and undergoes convergent extension so it now lies as a rod underneath the neural plate
60
Describe invagination
Epithelial sheet bends inwards
61
Describe ingression
Where individual cells leave an epithelial sheet and become freely migrating mesenchyme
62
Describe involution
An epithelial sheet bends inward forming an underlying layer
63
Describe epiboly
Sheet of cells which streches by thinning
64
Describe intercalation
Row of cells which moves between one another creating an array of cells that is longer and thinner
65
Describe convergent extension
When rows of cells intercalate but this intercalation is highly directional
66
What is the anterior endoderm and prechordal mesoderm in close contact with
The pahrynx and ventral forebrain
67
Describe the process of the Organiser Graft expt
| Who performed it and when
Speeman and Mangold - 1920
| Organiser grafted from newt into a second newt - found that a twinned secondary axis was formed
68
What are the conclusions from the Organiser Graft expt
2nd neural tube was host derived shows that the neural tissue was induced from the ectoderm in response to signalling from the organsier
The axial mesoderm (precordal mesoderm and notochord) and anterior endoderm was donor derived and therefore differentiates from the organiser
69
How were BMP antagonists discovered?
Extracted all the mRNA from the organiser cells and reverse transcribe to cDNA
Each then tested for a gene/protein which mimiced the action of the organisers ability to induce a secondary neural plate
70
What occurs at the Speeman organiser
Gsc upregulated
Leads to upregulation of chordin, noggin and follistatin
Leads to inhibition of BMP signalling
Leads to induction of a nerual cell fate
71
What are features of neural inducers in the organiser
Molecules must be expressed in the organiser
Must be secreted and act of adjacent cells
Overexpression in an ectopic site should lead to induction of a secondary axis
Inhibition should prevent the formation of any neural tissue - and any formation of the axis
72
Describe how the neural tube is formed
Cells of the nerual plate have apical-basal polarity
On the apical side - band of F-actin, when this contracts, the cells are forced to change their shape (constriction at the apical edge of the cell)
MANY MOLECULES ARE DIFFERENTIALLY DISTRIBUTED AT THE APICAL AND BASAL EDGES - AND MAY INTERACT WITH F ACTION CAUSING THE CONTRACTION AND SUBSEQUENT SHAPE CHANGE
73
Describe the role of follate receptors in spinofiida
Expressed on the apical domains of cells of the neural plate - when folate (derived from folic acid)
When folic acid defficient not enough contraction of the F-actin leads to the neural tube not closing properly
