CSB328H1 Study Guide - Midterm Guide: Gene Duplication, Syncytium, Morning Sickness
8 Jun 2018
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CSB328 LECTURE NOTES -PART 2 AFTER MIDTERM
LECTURE 13 Muscle Stem Cells
Muscle Regeneration and Repair: Muscle stem cells
Satellite cells = muscle stem cells
Division patterns of satellite cells
A: Asymmetric division of stem cell
daughter cells have different
fates
B:
symmetric division of stem
cell both daughter cells
are stem cells
C: symmetric division of
committed progenitor cell transient amplification
Pax7 markers for stem cells
Myf5 marker for muscle progenitor
Exercising mouse
What causes satellite cells to divide and undergo mitosis
when muscle injured?
- Process triggered by FGF signalling injured
muscle secrete FGF2
- FGF2 bind to FGFR1 signal transduction
- Mitosis eventually allow muscle repair
The FGF signalling pathway is a Receptor Tyrosine
Kinase (RTK) signalling pathway
- ERK = transcription factor
- FGF= ligand
- Molecule lead to transduction
- RAF – cascade of kinase and phosphorylation
Receptors move to lower part of dividing cell
undergoes very active FGF signaling
Cell that didn’t do much replace other cell express
pax7 enter quiescence **
Cell that received the signals express pax7 and Myf5
large production of these committed progenitor cells
**
- Expression of MyoD triggers muscle
differentiation **
Inducible gene expression system
- Want to induce expression of gene in particular
place/time – want to induce so we have control
of when/where expressed
Artificial gene construct that consist of an operator from
a bacterial operon and the coding region of mammalian
histone 2B fused to the coding sequence for jelly fish
GFP
Dox binding enables Tet-on to bind to the tet operator
and activate transcription of H2B::GFP
H2B::GFP is used to package DNA after replication
Dox antibiotic bind to tet-on transcription factor
conformational change bind to tet-operator -
induce transcription
Analysis of the satellite cell division frequency
Have construct in mice feed doxycycline
- As soon as histone 2B made wrap around
DNA
- Dox diluted as cells divide
- After a while GFP labeled histone replaced by
unlabeled histones
Repeated experiment with young and old mice
- Isolate all pax 7 (muscle stem/satellite) cells and
test for level of H2B:: GFP
- Data show that stem cells of old mice retain less
GFP than stem cells of young mice muscle
stem cells divide more of old mice divide more
often? (paradoxical)
Fate of muscle stem cells in young and old mice
- Young have more pax7 than old mice
- Old mice have higher % cell death
- In old mice more cells that express Myogenin
more cells undergoing differentiation
In older mice, the balance between stem cell renewal
and differentiation is disrupted: Stem cells from old
mice are more prone to lose their stem cell character
(they lose Pax7, start to express muscle differentiation
factors, and undergo apoptosis) than stem cells from
young mice. Additional experiments indicated that the
increased loss of muscle stem cells in old mice is linked
to their increased cell division rate.
Quiescence of satellite cells is important for their
maintenance
LECTURE 14 Muscle stem cells & AP Pattern formation
Muscle stem cells (satellite cells) muscle
regeneration and repair
- young mice are better muscle builders than old
mice
- Research by Chakkalakal indicates: satellite cells
divide more often in old mice, and increase loss
of satellite cells in old mice
Why satellite cells divide more often in older mice
FGF signaling when injured muscle fiber signal
cascade promoted division
When not exercising no or little FGF signaling no
inhibition of Sprouty1 Sprouty1 inhibit FGF signaling
pathway stem cell quiescent maintains stem cells
- Outputs of this pathway: triggering mitosis and
inhibiting expression of Sprouty1 gene
- FGF signaling potent inhibitor of Sprouty1
and Sprouty1 potent inhibitor of FGF signaling
To activate pathway:
- If K.O Spouty1 frequently undergo division
- Increase ligand activation of pathway inhib.
Spouty1 even more active
Document Summary
Process triggered by fgf signalling injured muscle secrete fgf2. The fgf signalling pathway is a receptor tyrosine. B: stem cells symmetric division of cell both daughter are stem cells. C: symmetric division of committed progenitor cell transient amplification. Raf cascade of kinase and phosphorylation. As soon as histone 2b made wrap around. Receptors move to lower part of dividing cell undergoes very active fgf signaling. Cell that did(cid:374)(cid:859)t do (cid:373)u(cid:272)h replace other cell express pax7 enter quiescence ** Cell that received the signals express pax7 and myf5. Large production of these committed progenitor cells. Want to induce expression of gene in particular place/time want to induce so we have control of when/where expressed. Artificial gene construct that consist of an operator from a bacterial operon and the coding region of mammalian histone 2b fused to the coding sequence for jelly fish. Dox binding enables tet-on to bind to the tet operator and activate transcription of h2b::gfp.
