Asymmetric Division in Muscle Stem Cells

1
Asymmetric Division in Muscle Stem Cells

• Christian Elabd, Ph.D.
• Joey Pham, B.A.

2
Muscle System

• - The muscle system is a model for quiescence
  (resting) and activity
• - Satellite cells, or muscle stem cells, can
  regenerate repeatedly
• - Satellite cells give rise to myoblasts
  (mostly), and fibroblasts, adipocytes,
  chondrocytes.

injured muscle
intact muscle
regenerated muscle
myonuclei
intact muscle
satellite cells
myofiber
Histology 2 weeks after injury Hematoxylin and
eosin cross section
Pictures from MJ Conboy, UC Berkeley
3
Muscle Regeneration
Quiescent Muscle Stem Cell
Myotrauma
Resting muscle Fiber
1) Activation
Multi-nucleation
Self Renewal
Return to resting state
Fusion to repair damaged muscle fibers
2) Proliferation
Fusion to produce new muscle fibers
3) Regeneration
4
Symmetric versus Asymmetric Division
Symmetry Asymmetry
Stem
Stem
Stem
Diff
Stem
self renewal
differentiation
Asymmetric Division Segregation of DNA, RNA or
Proteins in one daughter cell
5
Symmetric versus Asymmetric Division in the
Context of Muscle


Satellite
Satellite
Option 1


Option 2
Myoblast
Myoblast
Satellite
Dividing Satellite


Option 3
Satellite
Myoblast
6
Asymmetric Division in the Context of Muscle
Hoechst
Sca-1
Desmin
Merge
Differentiated cells are Desmin positive.
Non-differentiated cells are Sca-1 positive.
Conboy MJ et al. PLoS Biol. 2007 Jul5(7)e182
7
Summary of Asymmetric Division
Hoechst
While most cells in the body divide strictly
symmetrically, stem cells have the ability to
divide asymmetrically as well. In the context of
muscle regeneration, asymmetric division may
allow for muscle regeneration without exhausting
the pool of satellite cells (or muscle stem
cells). Understanding the mechanism of
asymmetric division is essential to advancing the
control of stem cell self-renewal versus
differentiation. Such control is necessary for
the use of stem cells in regenerative medicine.

Desmin
Sca-1
Merge