Regeneration Flashcards
What is regeneration?
Is the ability of adult organisms to replace missing tissues or organs through growth and repatterning of somatic tissues - distinct from homeostatic maintenance of tissues/organs
What are the two types of regeneration?
Morphallaxis and epimorphosis
What is morphallaxis
Morphallaxis- not much growth, new positional values are first established. What is left knows what is missing and re patterns itself creating a smaller strucuture
What is epimorphosis?
gorwth of a new patterned strucutre. What is left knows what is missing and regrows and patterns itself creating a creating the original structure
What is hydras way of regeneration?
Remodelling
What is the way planarians regenerate?
Remodelling and the proliferation of stem cells
What is the regeneration of vertebrates?
Stem cell proliferation and de and transdifferentiation
What is a Blastema?
Blastema: a mass of undifferentiated (de-differentiated) cells under the wound epidermis gives rise to the structures distal to the cut
What induces a secondary axis in hydra?
A hypostome - head - acts as an organiser
THE Head of hydra produces a signal that does what?
Inhibits secondary axis induction
What can Blastema cells give rise to?
Cartilage, skin, connective tissue and muscle
What happens to adult skeletal muscle in regeneration. What is the process
Undergoes dedifferentiation, multinucleate post mitotic> mononuclear proliferative cells
• This process involves phosphorylation of the cell-cell control protein Rb (retinoblastoma) which inactivates the protein
• Re-entry into cell cycle also involves thrombin
• Thrombin is a proteolitic enzyme first described as part of the blood clotting cascade
• Dedifferentiaiton also involves activation of Msx1, a homeobox TF which prevents muscle differentiation
Macrophages are required for limb regeneration. What happens if they are depleted in axolotl?
Blocks regeneration
Stumps can regernerate upon re-amputation, if macrophages are reintroduced
What essential growth factor do nerves induce?
Anterior gradient growth factor- Produced by wound epidermis
What can alter proximal-distal identity of the Blastema? How?
Retinoic acid - As increases expression of pod1, providing a potential mechanical of proximilasation at least in part
How does proximilisation of regenerating limb by retinoic acid occur.
Proximilisation of regenerating limb by retinoic acid
* retinoic acid acts through retinoic acid receptors, nuclear transcription factors
* Distal Blastema cells expressing a thyroxine- inaudible version of retinoic acid receptor (RAR) move to more proximal positions in response to thyroxine
* RAR is sufficient to mediate proximalisaiton
What are planarian stem cells called?
Neoblasts
What are the properties of neoblasts?
Highly proliferative, high nuclear cytoplasmic ratio, a single endoblatst can rescue a lethally irradiated work- pluripotent, clonogenic, endoblast
They are numerous and wide spread
How do neoblasts respond to injury?
Increase proliferation- first peak is 6 hours post injury’s- not specific for small incision vs large amputations
Second peak 48 hours post nature
Injury induces rapid increase in cell earths - 4 hour post injury- second 48 hours atre
How many wnt/b-catenin is need for head specification?
Low levels needed
How much wnt/b-catenin is needed for tail specification
High
What happens if an inhibitor APC is removed>
A tail grows after anterior amputation instead of head
What happens if b-catenin removed
Head grows after posterior amputation instead of tail
What happens if remove b-catenin without amputation?
Ectopic head form A-P constantly maintained
What does treatment of MEK inhibitor do?
Blocks regeneration. - Removal of this inhibitor does not end to regeneration unless new injuries and inflicted
