Lineage Tracing For The Study Of Regeneration In Vivo Flashcards
What was the aim of these studies?
To demonstrate the regeneration in myocardial tissue in vivo subsequent to a lesion
Who performed the experiments?
Hsieh at Harvard
Fully describe the 2 transgenic mous lines used in the experiment and the offspring when the two lines are crossed
The first transgenic mouse line expresses cre recombinase - the promoter in the experiment is cardiomyocte specific
The second mouse line constitutively expresses beta-galactosidase - which is also cardiomyocyte specific. This locus is targeted with cre recombinase substrate sequences.
Therefore when the 2 lines are crossed, this locus (b-gal) is found in the same cell that express CRE under this promoter - the locus is rearranged (recombination occurs). As a result:
- B-galactosidase expression is lost
- Expression of GFP is induced (GFP = green fluorescent protein, a genetic marker)
The result of cre activity is a switch from a b-gal+/GFP- cell to a b-gal-/GFP+ cell
What do we expect to see if we induce an infarction in the F1?
A pool of cells which survive and other cells that repopulate the infarcted area
Remember: GFP+ cells are mature cardiomyoctes
GFP- cells must derive from a different compartment - stem cell compartment
The proportion of GFP+ and GFP- cells present in the heart is observed
After F1 has infarction, the number of GFP+ cells decreases, and GFP- cells increases. This suggests that modest regeneration occurs though the local population of stem cells
It was noted that in the ageing F1, the frequency of GFP- expressing cells did not change. What does this suggest?
This means that there is no turnover, and no new cardiomyocytes are produced later in life
Where may the potential for therapy (to enhance the regenerative process) lie?
In understanding the signals that control these local populations of stem cells
