L13 Regeneration

Question 1

how long does it take for xenopus tail to regenerate

Answer 1

7 days

Question 2

what tissues present in teh regenerating tail at different time points

Answer 2

axons always present

muscles/vasculature appear later (48-72 hrs)

Question 3

what biological activities define the different time points of of the regeneration of xenopus tail

Answer 3

early - wound healing / inflamm response
mid - production of blastema like tissue /localised cell prolif
late - vascular/neuronal/muscle regen

Question 4

what do microarray show

Answer 4

label cDNA diff colours
chip is the antisense with known genes
allow estimation of the gene up reg / down reg dependent on the colour expr

Question 5

what did microarray experiments show

Answer 5

that genes invovled in metabolism are upreg v quickly after amputation
also emzyme involved in ros incr in reg tail

Question 6

what did live imagin of xenopus tail show

Answer 6

that ROS levels are inc in regen tail

Question 7

what is nox

Answer 7

enzyme complex main source of cellular ros

Question 8

what occurs to tail regen if inh ros

Answer 8

no tail regen

Question 9

what happen to ros levels in embryogenesis

Answer 9

are high

Question 10

what occurs whne a reducing egen is applied during embroyogenesis

Answer 10

defect in gastrulation

AP axis/muscle/brain effected

Question 11

what model org used to test if regen is a return to embryogen state

Answer 11

limb regen in xenopus

Question 12

what are some of the differences between limb regeneration and limb devleopment

Answer 12

size bigger in regen
more cell types in regen
immune reponse in regen
regen relies on nerves

Question 13

what are the two strucutres required for regeneration and their roels

Answer 13

AEC - apical ectodermal cap, requires blastema formation
blastem , mesenchymal orgin v prolif , simple growth zone which appears from milieu of cells is able to read pos of pd axis

Question 14

what are the development strucutres equivalent of AEC and blastema

Answer 14

AER

progress zone

Question 15

what is th eoutcome of the experiment in which P or D cells graft onto proximal stump

Answer 15

d stays stell on d
p cells go to both sides of limbs
= blastem cells know pos

Question 16

what is th eoutcome of the experiment in which hand amputated then reinserted with the proximal-distal axis inverted

Answer 16

both cases regow a hand
the blastema only regenrate distal structures
eg - cannont regen shoulder from a elbow

Question 17

what is prod1

Answer 17

a glycoprotein expressed in a graded fashion in the limv

Question 18

describe experiment manipulating a distal transformation

Answer 18

overexpr prod1 and graft blastema cells
=d cells go along pd axis
incr retinoic acid treatment can transform elbow to shoulder = cells respond in a dose dependent manner

Question 19

what signalling pathways involved in regen

Answer 19

hedgehog
fgf8
sonic hedehog
wnt 
fgf20

Question 20

what is the role of shh and fgf8 in regenerating limb

Answer 20

shh at posterior in blastema
fgf8 at anterior in blastema
interaction needed for limb regen

Question 21

what is the role of wnt in the regeneratign limb

Answer 21

decr after amputation
then incr after 24hrs
as decr nxn at amputation a pr which modulate wnt

Question 22

what is the role of fgf20 in limb regen

Answer 22

a target of wnt 
is upreg at regen 
decr in tadpole with ros inh
morphlino of it wound heals but no full regen 
- req for axial tissue not epidermal

Question 23

has science been able to regen limb

Answer 23

use factors to decr the immune response
bead with correct signals
results in partial regrowth not perfect regen