Facilitator Questions

1. What is the neurotrophic hypothesis, and how could the mechanism proposed serve to regulate nerve cell numbers in the nervous system.

 

2. How does oligodendrocyte death during optic nerve development help match the number of oligodendrocytes to the number of axons in the nerve?

 

3. What is the evidence that oligodendrocyte death during optic nerve development helps adjust oligodendrocyte numbers to the number of axons in the nerve?

 

4. What is the evidence that the neuregulin GGF is one of the axon-derived survival signals for oligodendrocytes in the developing rodent optic nerve?

 

5. What is the evidence that OPCs have a cell-intrinsic mechanism that helps determine when they stop dividing and differentiate?

What is the reason for calling the mechanism that helps determine when OPCs stop dividing and differentiate a cell-intrinsic timer rather than a counter?

 

6. What is the evidence that the cell-intrinsic timer in OPCs is regulated by extracellular signals from other cells?

 

7. What is the role of thyroid hormone in oligodendrocyte development?

 

8. What might be the advantage of having a hormone regulate a cell-intrinsic timer like the one that operates in OPCs?



9. Both p27 and Id4 seem to be part of the intrinsic timer in OPCs. What happens to their levels as OPCs proliferate? How are these levels controlled, and how do we know?

 

10. We are about 3000 times larger than a mouse. What cell mechanisms might explain this difference in size?