Diff12 - 33

Question 1

What are the two forms of regeneration possible?

Answer 1

Morphallaxis and epimorphosis

Question 2

What is morphallaxis?

Answer 2

Repatterning without growth

Question 3

What is epimorphosis?

Answer 3

Regeneration by regrowth

Question 4

What can urodele regenerate?

Answer 4

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

Question 5

What is special about urodele lens regeneration?

Answer 5

Occurs from iris - cells need to transdifferntiate

Question 6

What kind of regeneration does urodele exhibit?

Answer 6

Epimorphosis

Question 7

What is essential for urodele regeneration?

Answer 7

Epithelial cells migrate over the wound surface

Question 8

What is important to realise about urodele regeneration?

Answer 8

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

Question 9

What is the name of the regenerating front?

Answer 9

Blastema

Question 10

What does de-differentiation of muscle cells require?

Answer 10

Local activation of thrombin, msx expression, Rb inactivation

Question 11

Are cells truly dedifferentiating in the blastema?

Answer 11

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

Question 12

According to what rules does urodele regeneration occur?

Answer 12

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

Question 13

How does the wound blastema decide what to regenerate?

Answer 13

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

Question 14

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

Answer 14

Cell adhesion

Question 15

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

Answer 15

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

Question 16

What is capable of manipulating positional value in limbs?

Answer 16

Retinoic Acid (RA)

Question 17

Characterise the effects of RA

Answer 17

Dose dependent - more = more proximal generated

Question 18

How might proximilisation by RA occur?

Answer 18

Upregulation meis homeobox genes and/or prod1

Question 19

What is prod1?

Answer 19

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

Question 20

Why can limbs never innervated still regenerate?

Answer 20

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

Question 21

What is interesting about the drosophila heart?

Answer 21

Ventricles can be regenerated

Question 22

What is suggested to facilitate drosophila ventricle regeneration?

Answer 22

FGF

Question 23

How does the drosophila ventricle regenerate?

Answer 23

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

Question 24

What is the alternative method considered in heart regeneration?

Answer 24

Scarring

Question 25

What regeneration occurs in mammals?

Answer 25

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

Question 26

Why is neuronal regeneration so strictly regulated?

Answer 26

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

Question 27

What germ layer are hydra without?

Answer 27

Mesoderm

Question 28

How do hydra maintain body size?

Answer 28

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

Question 29

What is interesting about positional values in hydra?

Answer 29

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

Question 30

Outline the signal gradients in hydra

Answer 30

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

Question 31

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

Answer 31

Wnt/Beta catenin

Question 32

Where is Wnt expressed in hydra?

Answer 32

Head and activated regenerating tip

Question 33

Outline the hydra Wnt pathway

Answer 33

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