lecture 9- regeneration Flashcards
(22 cards)
what is morphallaxis
repatterning of existing tissue
what is epimorphosis
new cells grow by formation of blastema then divide and re differentiate
how has it been show in morphallaxis that growth isnt required
inhibit cell division
cells still regenerate
what are the 2 gradients needed for morphallaxis in hydra
1)gradient in positional value
2) head inhibitor gradient
what does the positional value determine
head inducing ability
resistance to inhibitor
describe the 3 experiments performed to show the presence of the inhibitor
1) when the inhibitor isnt removed, region 1 of hydra cant induce a head in region 2
2) when the head/head inhibitor is removed, region 1 can induce a head at region 1 and at region 2
3) when head is kept on and region 1 is added very far down hydra, it can form head due to low levels of inhibitor
what 2 experiments can be done to show the effect of the positional value
1)remove head
then add region 1 to a host hydra after 6 hrs
2nd head grows in region 2 dues to the positional valuer changing
2) remove top half of hydra
then add to host after 30hrs
same result
which signalling determines top positional value
Wnt/Beta Catenin
describe the process of epimorphosis after limb aputation
1) epidermal cells migrate to cover wound
2) cells below epithelium dedifferentiate and gather to form blastema
3)blastema divides and cells regenerate into dermis/cartilage/muscle
which signals are requires for redifferentiation of cells
thrombin
Msx1
pRB
how has it been shown that limb epimorphosis doesnt produce a carbon copy
cells dont go back to being stem cells
only dermis and epidermis cells can transdifferentiate
what are the rules of regeneration in limbs
always distal to wound
occurs according to positional value at site of cut
doesnt just replace missing parts
how does the wound know which cells should be distal and which should be proximal
different levels of cadherins expressed
more cadherins->stronger adhesion = proximal
less cadherins -> weaker adhesion =distal
what can proximalise a blastema and how
retinoic acid
by upregulating prod 1
what are the 3 experiments showing how innervation is involved in epimorphosis
1) cut arm with nerve in = arm will grow back as nAG can do the nerves job in supporting outgrowth and binding prod 1
2)cut denervated limb= no nAG at all do no regeneration
3) cut arm with no nerve to start off with = has epidermal nAG so this regenerates the limb
what happens to the epidermal nAG when a nerve grows and innervates
it disappears
describe regeneration in cockroaches
sense discontinuities in positional values
only respond locally
describe regeneration in mammals(PNS and CNS)
PNS can regrow axons but not neurons or schwann cells
CNS cant regenerate much as its non permissive
describe what happens in hydra when you remove the head and why this causes a smaller hydra to be formed
no head= no head inhibitor
so increase in positional value
cells with highest PV will start to make the head cells and therefore the head inhibitor
this reestablishes the original shape but as there hasnt been any growth, the hydra is smaller
which type of structure is regenerated at higher levels when there is a high level of retanoic acid
proximal structures
what is the role of neuregulin in heart regeneration
stimulates cardiomyte cell division and proleferation
what is the process of heart regeneration in a zebrafish
endocard will be activated and start expressing Raldh2
In addition the epicardium will become activated, expand rapidly and start to cover the wound.
The epicard will signal to the muscle below causing dedifferentiation.
Newly forming muscle expresses FGF
Epicardial cells respond to this signal by reforming blood vessel
The growing muscle will lead to dissolution of the clot
