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BMS249 Dev Neurobiology > L3/4 - Neural plate formation + neural induction > Flashcards

L3/4 - Neural plate formation + neural induction Flashcards

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

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2
Q

What feature of NS formation is found only n invertebrates

A

Delamination forming the neruoblast cells

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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

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4
Q

What would happen if all of the cells took their default state

A

All would become skin

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5
Q

Define differentiation

A

Process by which cells are able to become different and acquire specialised properties

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6
Q

What is cell differentiation governed by

A

Changes in gene expression which influences the repertoire of proteins expressed in a cell

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7
Q

Over time what happens to specialisation and pluripotency

A

Spec inc

P.P dec

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8
Q

Is BMP found is vertebrates of invertebrates

Give an example of an organism it is found in

A

Vertebrtes

Xenopus

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9
Q

Is Dpp found in vertebrates or invertebrates

Give an example of an organism it is found in

A

Invertebrates

Drosophila

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10
Q

BMP7 homologue in drosophila

A

Screw

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11
Q

What does BMP stand for

A

Bone morphogenic protein

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12
Q

What does dpp stand for

A

Decapentaplegic

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13
Q

BMP1 homologue is drosophila

A

Tolloid

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14
Q

BMP4 homologue is drosophila

A

Dpp

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15
Q

Chordin homologue is drosophila

A

Short gastrulation (SOG)

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16
Q

Screw homologue in xenopus

A

BMP7

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17
Q

Dpp homologue in xenopus

A

BMP4

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18
Q

Tolloid homologue in xenopus

A

BMP1

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19
Q

SOG homologue in xenopus

A

Chordin

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20
Q

Normal function of Chordin/SOG

A

Inhibition of BMP/dpp signalling

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21
Q

What is the normal function of BMP4 and dpp

A

The activation of non-neural homeobox genes

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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
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23
Q

What are the 3(4) components of the SMAD transcriptional complex

A

PHOSPHORYLATED R-SMAD
SMAD4
Co factor

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24
Q

What two antagonists inhibit BMP signalling

A

Noggin and chordin

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25
Q

What is the function of noggin

A

Causes the inactivation of SMAD4

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26
Q

What are BMP and chordin examples of

A

Genes that have been conserved throughout evolution

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27
Q

What are the two mechanisms by which chordin and sog act as antagonists of the BMP/dpp signalling pathwat

A

Act as a sponge moping up dpp/bmp (binding to and inactivating)
Competitively bind at receptors preventing binding of dpp/bmp

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28
Q

What does Dpp and SOG broadly dictate

A

The dorsal and ventral axis

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29
Q

What genes are expressed on the dorsal side of the embryo (insect)

A

Dpp, tld, tsg and SV-2

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30
Q

Describe the activity of the dpp pathway on the dorsal side of the embryo (insect)

A

No inhibition of the dpp pathway

31
Q

What cell fate is taken by cells on the dorsal side of the embryo (insect)

A

Epidermal

32
Q

What genes are expressed on the ventral side of the insect embryo

A

Sog and screw

33
Q

What is the action of SOG

A

Inhibition of dpp binding to its receptor

34
Q

What fate is taken by cells on the ventral side of the cell

A

Neural cell fate - neurogenic region is formed

35
Q

What side is the NS found in insects

A

Ventral

36
Q

What side is the NS found in vertebrates

A

Dorsal

37
Q

Why is there a difference between the sides which the NS is found in vertebrates and invertebrates

A

Possibly due to a rotation of the head

38
Q

Genes expressed at the dorsal end of a vertebrate - what fate do these cells then take

A

Chordin and Admp cells take a nerual cell fate

39
Q

Genes expressed at the ventral end of an invertebrate

What fate do these cells take

A

Sog, Screw

40
Q

Molecular pathway

ECTODERM IN PRESSENCE OF BMP SIGNALLING

A

High SMAD1 and low SMAD1
Msx1, GATA1, Vent (epidermalising transcription factors)
LEF1
Epidermal differentiation

41
Q

Molecular pathway

ECTODERM WITHOUT BMP SIGNALLING

A 
Low SMAD1 and high SMAD7 
Xlpou2, SOXd/B (neuralising transcription factors)
Neurogenin
NeuroD
Neural differentiation
42
Q

What process results in the formation of the neural tub

A

Neuralation

Neural plate rolls up to form the neural tube

43
Q

What occurs during spinobifia

A

Failure of the neural tube to close properly

44
Q

What can reduce the chances of spinobifida occuring

A

Folic acid

45
Q

How do we know there are 3 germ layers found in the embryo

A

Repitore of proteins expressed - use of an antibody stain

mRNA being expressed - look at using an in-situ hybridisation

46
Q

What sets up the polarity of the early embryo

A

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
Q

Which part of the embryo is fated to become the furture CNS

A

Cells immediatly adjacent to the organiser

48
Q

What signal does the organiser secrete … what does this lead to

A

GSC is expressed this acts to upregulate Chordin , Noggin and Follistatin
These secreted molecules act to inhibit BMP signalling

49
Q

What the result of BMP signalling inhibiton

A

Neural plate induction

50
Q

What are some antagonists of the BMP signalling pathways

A

Chordin
Noggin
Follistatin

51
Q

Outline the stages of mesoderm induction and patterning

A

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
Q

What receptors do BMPs bind to

A

TGFb-R

53
Q

How to BMPs tend to act

A

Locally and diffuse to neigbouring cells

54
Q

What fate do cells take if BMP signalling is active

A

Cells take an ectodermal cell fate

55
Q

How do chordin noggin and follistatin act as inhibitors of the BMP signalling pathway

A

Antagonists compete for BMP binding - no longer able to activate receptors and cause activation of the BMP pathway

56
Q

What is different in the development of chicks and humans

A

flattened into three sheets not a hollow sphere

57
Q

What do cells in the organiser differentiate into

A

Axail mesendoderm and anteiror endoderm

58
Q

What makes up the axial mesendoderm

A

Anteior endoderm, precordal mesoderm, notochord

59
Q

What then happens to the axial mesendoderm

A

Involute, intercalates and undergoes convergent extension so it now lies as a rod underneath the neural plate

60
Q

Describe invagination

A

Epithelial sheet bends inwards

61
Q

Describe ingression

A

Where individual cells leave an epithelial sheet and become freely migrating mesenchyme

62
Q

Describe involution

A

An epithelial sheet bends inward forming an underlying layer

63
Q

Describe epiboly

A

Sheet of cells which streches by thinning

64
Q

Describe intercalation

A

Row of cells which moves between one another creating an array of cells that is longer and thinner

65
Q

Describe convergent extension

A

When rows of cells intercalate but this intercalation is highly directional

66
Q

What is the anterior endoderm and prechordal mesoderm in close contact with

A

The pahrynx and ventral forebrain

67
Q

Describe the process of the Organiser Graft expt

Who performed it and when

A

Speeman and Mangold - 1920

Organiser grafted from newt into a second newt - found that a twinned secondary axis was formed

68
Q

What are the conclusions from the Organiser Graft expt

A

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
Q

How were BMP antagonists discovered?

A

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
Q

What occurs at the Speeman organiser

A

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
Q

What are features of neural inducers in the organiser

A

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
Q

Describe how the neural tube is formed

A

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
Q

Describe the role of follate receptors in spinofiida

A

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

BMS249 Dev Neurobiology (16 decks)

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