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Y2S2 - Differentiation > Diff12 - 33 > Flashcards

Diff12 - 33 Flashcards

1
Q

What are the two forms of regeneration possible?

A

Morphallaxis and epimorphosis

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2
Q

What is morphallaxis?

A

Repatterning without growth

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3
Q

What is epimorphosis?

A

Regeneration by regrowth

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4
Q

What can urodele regenerate?

A

Dorsal crest, limbs, retina, lens, jaw, tail

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5
Q

What is special about urodele lens regeneration?

A

Occurs from iris - cells need to transdifferntiate

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6
Q

What kind of regeneration does urodele exhibit?

A

Epimorphosis

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7
Q

What is essential for urodele regeneration?

A

Epithelial cells migrate over the wound surface

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8
Q

What is important to realise about urodele regeneration?

A

System for regeneration MUST be different to generation in ebryogenesis - otherwise the morphogens would have to magically act over a 10x larger distance!

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9
Q

What is the name of the regenerating front?

A

Blastema

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10
Q

What does de-differentiation of muscle cells require?

A

Local activation of thrombin, msx expression, Rb inactivation

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11
Q

Are cells truly dedifferentiating in the blastema?

A

No - muscle cells only become muscle, Schwann only Schwann; Sort of - dermis can become dermis OR cartilage

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12
Q

According to what rules does urodele regeneration occur?

A

All regeneration always distal to wound, according to positional value at the site of the wound; regeneration is dependent on innervation unless the limb never had a nerve

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13
Q

How does the wound blastema decide what to regenerate?

A

Reads loacl positional value and generates more distal positional values - it does not determine what is missing

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14
Q

What is thought to be important in positional value in limbs?

A

Cell adhesion

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15
Q

Why is cell adhesion thought to be important in positional value in limbs?

A

If distal is combined with proximal blastema, proximal engulfs distal, inferring distal self-stick and proximal stick more to distal than self

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16
Q

What is capable of manipulating positional value in limbs?

A

Retinoic Acid (RA)

17
Q

Characterise the effects of RA

A

Dose dependent - more = more proximal generated

18
Q

How might proximilisation by RA occur?

A

Upregulation meis homeobox genes and/or prod1

19
Q

What is prod1?

A

Protein expresed at the highest level in the proximal regenerating blastema - induced by RA treatment

20
Q

Why can limbs never innervated still regenerate?

A

It was shown that a molecule called newt anterior gradient (nAG) can rescue regeneration of denervated limb

21
Q

What is interesting about the drosophila heart?

A

Ventricles can be regenerated

22
Q

What is suggested to facilitate drosophila ventricle regeneration?

A

FGF

23
Q

How does the drosophila ventricle regenerate?

A

Bleeding > blood clot > cardiomyocytic dedifferentiation and proliferation > epicardium covering of wound > new muscle express FGF > induces epicardial creation of new blood vessels to support new ventricle

24
Q

What is the alternative method considered in heart regeneration?

A

Scarring

25
Q

What regeneration occurs in mammals?

A

Tips of fingers, axons (if neuron survives), liver, ribs (if periosteum intact)

26
Q

Why is neuronal regeneration so strictly regulated?

A

CNS is very delicate and elaborate - disrupted easily if regeneration was so easy

27
Q

What germ layer are hydra without?

A

Mesoderm

28
Q

How do hydra maintain body size?

A

Loss of cells through basal disc (end of tentacle) and asexual budding

29
Q

What is interesting about positional values in hydra?

A

They must continually change, as cells constantly move up the hydra

30
Q

Outline the signal gradients in hydra

A

Positional value - 1 high, 5 low ability to induce head; head inhibitor - produced in head

31
Q

What molecular mechanics are thought to be involved in hydra head patterning?

A

Wnt/Beta catenin

32
Q

Where is Wnt expressed in hydra?

A

Head and activated regenerating tip

33
Q

Outline the hydra Wnt pathway

A

Decreased GSK3-b > increased nuclear beta catenin > activation of Wnt

Y2S2 - Differentiation (15 decks)

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