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y2s2 - differentiation > Diff5 - 36 > Flashcards

Diff5 - 36 Flashcards

1
Q

What causes different cytoplasmic determinants to sink in the egg?

A

Gravity in xenopus, placenta interaction in mammals

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2
Q

What does cytoplasmic determinants sinking cause?

A

Cells in this region to be different - they then have specific transcription factors localised and activated

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3
Q

What specific transcription factors are localised and activated in the Xenopus egg?

A

Vegetal portion - the heavy yolk - has VgT activated

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4
Q

What is VgT?

A

T box transcription factor

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5
Q

What does the vegetal section induce?

A

Dorsal and ventral mesoderm

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6
Q

Example of dorsal mesoderm derivative

A

Notochord

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7
Q

Example of ventral mesoderm derivative

A

Blood

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8
Q

Why are two forms of mesoderm induced by vegetal section?

A

Differential gene expression

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9
Q

What causes differential gene expression in the vegetal section?

A

Sperm induced cortical rotation

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10
Q

What does sperm induced cortical rotation cause the expression of?

A

Wnt signalling from the dorsal side

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11
Q

What does activation of Wnt signalling lead to?

A

The stabilisation of a factor called beta-catenin, which enters the nucleus and changes the transcriptional profile

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12
Q

What does Wnt bind to?

A

Frizzled

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13
Q

What does frizzled signal to?

A

Dishevelled

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14
Q

What does dishevelled interact with?

A

Axin - to prevent GSK3 from degrading free beta-catenin

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15
Q

How does Wnt induce a difference in vegetal cells?

A

Wnt on the dorsal side, VgT on vegetal = 3 dimensional gradient

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16
Q

What is the region of Nodal and Wnt expression overlap called?

A

Nieuwkoop centre

17
Q

What is the name for Nieuwkoop progeny?

A

Organiser/Dorsal mesoderm

18
Q

Summarise early morphogenetic gradients in the Xenopus embryo

A
19
Q

Outline the properties of the organiser

A

Ability to self-differentiate into axial mesoderm, ability to dorsalise adjacent mesoderm, ability to induce adjacent extoderm to a neural fate

20
Q

What controls the properties of the organiser?

A

Siamois, then goosecoid later

21
Q

What is the axial mesoderm?

A

Rod of cells around which the future body’s axis forms

22
Q

How is the axial mesoderm created?

A

Convergent extension - cells in a circle or sheet, then all desperately want to be in the centre

23
Q

What three cell types form axial mesoderm?

A

Prechordal mesendoderm, prechordal mesoderm, notochord

24
Q

What form dorsal aspects of the axial mesoderm?

A

Prechordal mesendoderm, prechordal mesoderm

25
Q

What is important to note about Nodal expression in the Xenopus?

A

Doesn’t differentiate all the way to the top of the animal hemisphere, only changes the fate of a band of animal hemisphere cells that areimmediately adjacent to the vegetal hemisphere.

26
Q

What does convergent extension cause in the developing embryo?

A

Complete change in shape - from sphere to larva-like shape

27
Q

Why does convergent extension cause a change in embryo shape?

A

The yolk from the yolky vegetal cells is being used, so they all but disappear; top animal cap cells now have the induced mesoderm cells arranged in rod-like sturcutres inside of them, running down the AP extent of the body

28
Q

What do the three main precursors form of the organiser region form?

A

Pharyngeal endoderm, prechordal mesoderm and notochord

29
Q

What does the rod follow during convergent extension?

A

Fibronectin rich pathways

30
Q

When does gastrulation occur in vertebrates?

A

Shortly after blastocyst stage, when the trophextoderm and inner cell masses have formed, and it has implanted into the uterine wall

31
Q

What causes gastrulation in vertebrates?

A

Signals coming from the developing placenta, forcing the ICM to start differentiating into hypoblast or epiblast

32
Q

What does epiblast go on to be?

A

Embryo proper - equivalent to Xenopus animal hemisphere

33
Q

What can the hypoblast be considered equivalent to?

A

Xenopus vegetal hemisphere

34
Q

Where does the vertebrate version of the Nieuwkoop centre form?

A

The hypoblast

35
Q

What does the organising part of the hypoblast induce?

A

Some epiblast cells to become mesoderm and definitive endoderm

36
Q

What occurs to the vertebrate organiser, and what does this form?

A

Moves from propective posterior to anterior, creating the primitive streak

y2s2 - differentiation (15 decks)

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