skeletal muscle regeneration

Question 1

embryological origin of skeletal muscle

Answer 1

paaraxial mesoderm

Question 2

origin of axial and limb skeletal muscles

Answer 2

para-axial mesoderm

Question 3

origin of vertebrae, ribs, tendons

Answer 3

sclerotome

Question 4

origin of bones and connective tissue in limbs

Answer 4

lateral plate mesoderm

Question 5

EMT effectors

Answer 5

growth factors, cytokines and ECM

Question 6

MET effects

Answer 6

adhesion, cortical actin,

Question 7

EMT

Answer 7

cellular interaction with ECM

concentration gradients

Question 8

MET

Answer 8

cell to cell interactions

Question 9

wnt signalling pathway

Answer 9

wnt –> firzzled –> disheveled –I GSK-3 –I beta-catenin –> transcription

Question 10

BMP signalling

Answer 10

need to dimeraise and bind protein - 2 receptors

Question 11

FGF signalling

Answer 11

ligand based- activation of TFs

non-ligand based due to cell adhesion molecules

Question 12

Myogenesis

Answer 12

1. non-committed muscle prescursor cells
   - drop in cell proliferation, drop in FGF and FGFr, drop in Id, rise in Pax7
2. committed myoblasts
   - myogenic TF induce skeletal muscle gene expression
3. immature myotube cell fusion
   - myognenin is expressed
4. myotube
5. developed muscle fibre, nuclei displaced under membrane

Question 13

myogenic TFs and myogenesis

Answer 13

basic Helix-loop-helix TF
Myf-5, MyoD, MRF4, myogenin
repressors = Id (HLH) and ImF

Myogenic TF bind to E proteins; Id socks up E proteins to lower MTFs-E protein complexes
HLH region allows two TF to bind
BAsic region binds to DNA motif
repressors are almost like myogenic TF but have NO basic region
regulators bind to MyoD but because there is no basic region it can’t bind to DNA. therfeore concentration dependent

Question 14

differentation of myoblast

Answer 14

induced by p21, p38 and Rb which prevents reentry into cell cycle

Question 15

mature vs nonmatrue myoblast

Answer 15

immautre = myogenin positive 
mature = desmin positive

Question 16

myoblast fusion to a myotube

Answer 16

myoblast allignment (cell-ECM) 
myoblast fusion (cell-cell adhesion followed by fision)

Question 17

myoblast fusion

Answer 17

1. fusion competent cell extend filopodia to myotube
2. cell-cll recognition
3. adhesion complexes
4. plaue formation
5. cell allignemnt and close apposition of plasma membrane
6. membrane breakdown and fusion pore formation
7. myotube

Question 18

formation of adhesion plaque

Answer 18

expression on the cell surface of cell surface receptors

Question 19

signalling pathway of mysin isotype expression (fast or slow)

Answer 19

tonic acctivity — slow motor neuron with small diamter. low calcium amplitude and long duration —> incrase in calcineurin —> dephosphorylation of NFAT

phasic activity —> fast motor neuron with large diameter
increased amplitude of calcium with short duration
phosphorylation of NFAT

Question 20

motor nerve activity

Answer 20

required for primary myotubule and not secondary

Question 21

satellite shape

Answer 21

round = satellite cell
cigar = myogenic TF

Question 22

myoD;myf5 ratio

Answer 22

myoD> myf5 - differentiation

myoD< Myf5 - proliferation and delyared differentation

Question 23

pax 7 :myoD ratio

Answer 23

Pax7 > MyoD - quiescent
Pax7 = MyoD- proliferation but not differentiation
Pax7 < MyoD- differentiation with activation of myogenein