Lecture 9 - Regeneration Flashcards

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1
Q

What are the 2 types of regeneration?

A

Morphalaxis and Epimorphasis

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2
Q

What is Morphalaxis ?

A

Cells rearrange themselves, no growth of cells, no cell proliferation. Repatterning

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3
Q

What is Epimorphasis ?

A

Cells are respecified, go through dediffrentiation
Limited transdifferentiation

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4
Q

What model organism we used to study regeneration?

A

Hydra - freshwater organism

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5
Q

What do Hydras have that allows them to regrow their head?

A

They have 2 gradients that allow them to regrow their head back
When head is removed it is formed again by respecifying cells.

  1. Head-inducing ability
  2. Head-inhibiting ability
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6
Q

What is a head-inducing abilty ?

A

Dependent on the positional value of the cells
If cell is closer to head. Higher head-inducing capability
Concentration increases as you go up

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7
Q

What is a head-inhibiting ability?

A

An inhibitor highly concentrated in the head region but low conc further down the hydra.
Conc decreases as you do down the body.

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8
Q

What are the 3 rules of regeneration?

A
  1. Always distal to the cut, regeneration goes forwards away from body
  2. Always according to the positional value of the cut - location of the cells within the body plan.
  3. Not just replacing the missing parts - not extrinsic mechanism, regenerating what meant to be after the cut
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9
Q

What is limb regeneration about?

A

Limb regeneration is all about cell dedifferentiation.

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10
Q

What is a Blastema ?

A

A group of cells that have dedifferentiated at a wound site

Dervided from dermis, cartilage and muscle (multi nuclear)
THROMBIN

Provides differentiation enviroment

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11
Q

Difference between distal and proximal Blastemas?

A

distal - More adhesive - cells stay together

proximal - less adhesive - tend to engulf distal blastemas - They have a molecule called PROD1 activated by retinoic acid. The higher the acid conc the more proximal the cells will be, their positional value is more proximal. Retinoic acid activates RARdelat2 which then activates PROD1

Tissues will remain separate

Anti-prod 1 can prevent engulfment.

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12
Q

Where is NAG present ?

A

Present in nerves (nerve sheath) and epidermis

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13
Q

What is the point of NAG ?

A

Allows regeneration of limbs

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14
Q

Can you still regenerate without NAG ?

A

When NAG is expressed in nerves, the NAG in the epidermis is downregulated. So if you have no nerves theoretically, NAG will be upregulated in the epidermis.

Innervation leads to downregulation of NAG

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15
Q

What proteins are expressed in the heart?

A

Endocardium - protein expressed called Raldh1
Epicardium - protein expressed called Neureglin - needed for myocyte proliferation

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16
Q

What happens when the heart is damaged ?

A

Endocardium is activated
Causes epicardium activation
Cells will expand over the endocardium to repair
To do that muscle dediffrentes and expresses FGF
And new blood vessels form

17
Q

Why can embryonic mice can regenerate their heart but adult ones cannot?

A

Embryonic mice can regenerate their heart, adult ones cannot.
Becuase in embryonic mass molecule ERBB2, a protein needed in neuregulin signal transduction. It is down-regulated after birth

18
Q
A

Positional value and head inhibitor decrease as you go down the body.

19
Q

Where is WNT and BEta-catenin activated ?

A

WNT and Beta-catenin are activated in the regeneration tip

20
Q
A

WNT ius involved in head formation and is activated in a regenerating tip.

Inhibition of GSK3beta activates Beta catenin and WNT