Lecture 9 - Regeneration Flashcards
What are the 2 types of regeneration?
Morphalaxis and Epimorphasis
What is Morphalaxis ?
Cells rearrange themselves, no growth of cells, no cell proliferation. Repatterning
What is Epimorphasis ?
Cells are respecified, go through dediffrentiation
Limited transdifferentiation
What model organism we used to study regeneration?
Hydra - freshwater organism
What do Hydras have that allows them to regrow their head?
They have 2 gradients that allow them to regrow their head back
When head is removed it is formed again by respecifying cells.
- Head-inducing ability
- Head-inhibiting ability
What is a head-inducing abilty ?
Dependent on the positional value of the cells
If cell is closer to head. Higher head-inducing capability
Concentration increases as you go up
What is a head-inhibiting ability?
An inhibitor highly concentrated in the head region but low conc further down the hydra.
Conc decreases as you do down the body.
What are the 3 rules of regeneration?
- Always distal to the cut, regeneration goes forwards away from body
- Always according to the positional value of the cut - location of the cells within the body plan.
- Not just replacing the missing parts - not extrinsic mechanism, regenerating what meant to be after the cut
What is limb regeneration about?
Limb regeneration is all about cell dedifferentiation.
What is a Blastema ?
A group of cells that have dedifferentiated at a wound site
Dervided from dermis, cartilage and muscle (multi nuclear)
THROMBIN
Provides differentiation enviroment
Difference between distal and proximal Blastemas?
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.
Where is NAG present ?
Present in nerves (nerve sheath) and epidermis
What is the point of NAG ?
Allows regeneration of limbs
Can you still regenerate without NAG ?
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
What proteins are expressed in the heart?
Endocardium - protein expressed called Raldh1
Epicardium - protein expressed called Neureglin - needed for myocyte proliferation
