Vertebrate development > Gastrulation > Flashcards

Gastrulation Flashcards

(44 cards)

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1
Q

Gastrulation

- purpose

A

> generate basic body plan

> specify anterior and posterior of embryo

> generate 3 germ layers

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2
Q

Gastrulation

- involves 2 processes

A

Cell migration + movement

Changes in cell-cell interactions
- cell adhesion

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3
Q

5 basic movements associated with gastrulation

A 
>Epiboly 
>Intercalation 
>Convergent extension 
>Delamination + ingression 
>Involution
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4
Q

Epiboly

A

Cell flatter along apiece-basal axis

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5
Q

Intercalation

A

Double cell layer becomes a single layer

as cells make new contacts with each other

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6
Q

Convergent extension

A

Multilayered sheets of cells become narrower

as cells make new contacts

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7
Q

Delamination and ingression

A

Individual cells change shape + lose contact with their neighbours
- cells become bottle shaped

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8
Q

Involution

A

Epithelium turns around on itself and spreads in direction opposite to basal margin

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9
Q

Amphibian gastrulation

A

Initiated along future dorsal side of embryo (just below equator)
- in the marginal zone

Cells invaginate to form blastopore

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10
Q

Stabilisation of Beta-catenin by Dsh

A

Initially b-catenin present throughout egg

Later degraded by GSK3 mediated phosphorylation
- only in ventral cells

This is prevented in dorsal region by inactivation of GSK3 by Dsh

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11
Q

Dsh

  • name
  • role
A

Dishevelled

Transported to dorsal region from vegetal region by cortical rotation
Protects b-catenin from degradation

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12
Q

Events leading to induction of the organiser

A

Stabilisation of b-catenin on dorsal site

b-catenin translocates to nucleus + associates with Tcf3

-> activation of transcription of Siamois

Siamois + Xlmi1 activated by Vg1 + Nodal
- critical for expression of organiser specific genes
= e.g. goosecoid

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13
Q

Nieuwkoop Centre and the organiser

  • induced by…
  • then specifies…
A

Dorsal most vegetal cell of blastula
- capable of inducing the organiser

The Nieuwkoop Centre specifies the organiser

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14
Q

Candidate molecule responsible for formation of Nieuwkoop Centre

A

B-catenin
= multifunctional protein

Behaves as an anchor for cell-membrane catherine
Can behave as a TF

Component of the Wnt/wingless signalling pathway

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15
Q

Gastrulation in mouse + chick

A

> Origin of PS marks posterior of embryo
Opposite end marks anterior
Dorsal side is where cells migrate inwards
Groove marks left + right

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16
Q

Types of tissue in blastocyst + early post-implantation embryo

A

EPI = Epiblast

PE = parietal endoderm
- primitive endoderm-derived cell population

emVE = Embryonic visceral endoderm
- subset of visceral endoderm cells

DVE = Distal visceral endoderm

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17
Q

Apposition of tissues in blastocyst + early post-implantation embryo

A

EPI - 1 of 3 cell lineages of late blastocyst

PE - forms by EMT, migrates + finally lies next to mural trophectoderm

emVE - overly the epiblast
- contribute to endoderm layer of visceral yolk sac + embryonic gut

DVE - located at distal tip of embryos
- containing the precursors of some of the AVE

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18
Q

Cavitation of epiblast at early post-implantation

- interplay of which 2 signals?

Study These Flashcards
A

promoting cell death vs promoting cell survival

19
Q

Cavitation of epiblast at early post-implantation

- 1st signal

Study These Flashcards
A

= death signal
Produced by adjacent layer of visceral endoderm cells

Acts over short distances to create cavity
- by inducing apoptosis of internal epiblast cells

20
Q

Cavitation of epiblast at early post-implantation

- 2nd signal

Study These Flashcards
A

= survival signal
Mediated through contact with basement membrane positioned at epiblast/visceral endoderm interface

Promotes survival of epiblast cells located adjacent to visceral endoderm

21
Q

Pre-gastrulation cell movement in VE

- general

Study These Flashcards
A

Mesoderm that’s 1st formed migrates posteriorly + will for extra-embryonic mesoderm

  • also moves around laterally + contributes to embryonic mesoderm
22
Q

Pattern of cell movement during embryogenesis

  • Pre-Gastrulation
  • step 1
Study These Flashcards
A

DVE cells move to prospective anterior side of embryo

-> forms AVE

23
Q

Pattern of cell movement during embryogenesis

  • Pre-Gastrulation
  • step 2
Study These Flashcards
A

Lateral movement of AVE after leading population reaches border of epiblast + the extra embryonic ectoderm

24
Q

Pattern of cell movement during embryogenesis

  • Pre-Gastrulation
  • step 3
Study These Flashcards
A

Distribution of VE cell clones that’re derived from ICM of blastocyst

25
Remodelling of the conceptus simultaneous with the onset of gastrulation
Thickening of the epiblast - marks posterior of embryo Cells from epiblast delaminate + ingress through the streak forming the mesoderm Anterior most part of primitive streak forms different things in different species
26
What does the anterior most part of the primitive streak form in mice, chicks and amphibians?
Mice = Node Chick = Hensen's node Amphibians = Spemann organiser
27
Early gastrulation cell movement | - general
Mesoderm in extra embryonic region develop intercellular lacunae - which then rise to form exocoelom Formation of amniotic folds
28
Early gastrulation cell movement | - step 1
Movement of endoderm accomplished by coordination of movement of AVE to extra embryonic yolk sac
29
Early gastrulation cell movement | - step 2
Anterior-proximal movement of more distally located VE
30
Early gastrulation cell movement | - step 3
Anterior displacement of definitive endoderm
31
Early gastrulation cell movement | - step 4
Movement of mesoderm commences with ingression of progenitor cells through the primitive streak
32
Early gastrulation cell movement | - step 5
Anterior spreading of the tissue sheet
33
Morphogenesis of mesoderm and endoderm
At the primitive streak - cells under EMT, ingress + migrate away to form mesoderm Cells fated to form the definitive endoderm undergo MET + egress into epithelium of emVE
34
Node | - what is it?
Group of (~200) specialised cells located at most anterior aspect of PS Equivalent of the organiser
35
Node | - what does it do?
Can induce additional anterior structures when transplanted into ventral side of Xenopus embryo Causes duplication of digits in developing avian embryo
36
Node | - heterotopic grafting
To a posterolateral position of the node | -> leads to induction of a 2nd neural axis
37
Network of signalling activity leading to patterning of the VE - step 1
In ExE - nodal precursor protein (produced by epiblast) acts by active receptors 1B + 2A to activate transcription of Furin + Pcsk6
38
Network of signalling activity leading to patterning of the VE - step 2
ExE secretes convertase enzymes encoded by Fruin + Pcsk6
39
Network of signalling activity leading to patterning of the VE - step 3
Convertase enzymes cleave the nodal precursor to processed Nodal
40
Network of signalling activity leading to patterning of the VE - step 4
Nodal signals from epiblast repress genes e.g. Hnf4, Gata4, Ttr + Furin - which are normally expressed in the ExVE after the DVE stage
41
Network of signalling activity leading to patterning of the VE - step 5
Simultaneously | nodal signals maintain expression of EmVE genes e.g. Lhx1, Fgf5...
42
Network of signalling activity leading to patterning of the VE - step 6
Nodal + GDF3 working with cripto (a co-receptor) - generate a proximal-distal gradient of signalling activity in the embryo = crucial for specification of DVE
43
2 signalling centres in mammals
Node - responsible for creation of body axis AVE - Node with signalling from AVE responsible for creation of anterior structures
44
Patterning of the anterior-posterior axis | - FGFs + RA
Expression of Nodal + gradients of Wnts, BMP + FGFs in the posterior part of the primitive streak FGF8 necessary for ingression of mesodermal cells through primitive streak RA gradient + FGF8 regulates AP patterning regulating the Hox through the Cdx genes

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