zhu lecture Flashcards
how are the number of cells, produced by neural stem cells, controlled in developing brains
1) length of cell cycle of neural stem cells
2) number of neural stem cells
3) proliferation period of neural stem cells
4) proliferation of daughter cells from neural stem cells
5) programmed cell death
interkinetic nuclear migration
apical progenitors. the nucleus migrates from the pial surface to the ventricular surface during s phase. it undergoes G2 phase and M phase at the V surface and then the nucleus migrates back to the pial surface
how do we know this?
vizualize it with radioactive thymidine labeling
positive regulators of the cell cycle.
growth factors, morphogens, upregulation of cyclins
negative regulators
TGF, P27kip
which phase in the cycle gets longer, allowing cells to eventually exit into Q
the G1 phase
how do we expand the progenitor pool
symmetric
symmetric divisions
two daughter cells receive the same progenitor identity. this occurs in early preneurogenesis.
what cleavage plane for symmetric
vertical, relative to the ventricular surface
neurogenesis
radial glial cells self-renew through asymmetrical divisions. cleavage plane is vertical, oblique or horizontal. asymmetric division produces new radial glia, and one differentiated cell, such as a postmitotic neuron.
which divisions cause asymmetric
horizontal or oblique
how do oblique/horizontal divisions cause asymmetric
this is through notch and numb localization. they are sequestered differently when there is an oblique division. this causes less inhibition of notch signaling and thus a progenitor state. whereas the cell that inherited more numb from the division has an inhibition of notch and thus a more neural phenotype.
what does notch signaling do?
it suppresses proneural genes, thus maintains progenitors.
what are apical progenitors
they are the radial glial cells that produce all the neural cells, through the production of intermediate progenitor cells
what are basal progenitors
they are the intermediate neural progenitors, found in the subventricular zone. they have multipolar processes without connections to the ventricular or pial surface. they DO NOT have interkinetic nuclear movement. they divide symmetrically with limited potential.
what explains the increased size in the mammalian brain
the large subventricular zone populated with basal progenitors and the expanded outer subventricular zone with oRGs.
