Discussion paper 10 Flashcards
What are the 2 zones of adult neurogenesis?
SGZ / dentate gyrus
SVZ
Neural stem cells of the SGZ become…
Granule cells
Neural stem cells of the SVZ become…
Olfactory interneurons (granule and periglomerular)
Why is it a challenge to study adult neurogenesis?
Because it is difficult to specifically target neuronal stem cells
What are the key features of the nestin:creERT2 that make it important for this paper?
Nestin is specific to proliferating neural stem cells
It is not expressed in post-mitotic, mature neurons
CreERT2 is the inducible version of cre!
What is used to induce the activity of creERT2?
Tamoxifen
Normal Cre (NOT CREERT2) Is localized…
In the nucleus (has NLS)
Describe how the inducible creERT2 works
Estrogen receptor cre: when it is inactive cre will be in the cytoplasm, then will bind to estrogen receptor t2 and localize to the nucleus to excise loxP
What are the key features of the ROSA:CFP line used in this paper?
ROSA is expressed in every cell in the body, and when not targeted by cre, will have a stop codon (no cfp expression)
However, when stop codon excised by cre, cfp will be permanently turned on so that these cells can be identified
What does crossing the nestin X rosa transgenes do?
Allows the authors to visualize cells that are nestin + in an UNBIASED way
Allows to authors to examine what these cells become
What percentage of nestin+ cells undergo tamoxifen-induced recombination? Why is this important?
67%, important because in later ablation experiments there are still 1/3 of the cells not being ablated
What are the main takeaways of this figure?
Labelling of the SGZ (dentate gyrus – gran cell) noticing the generation of new granule cells
Noticing the generation of new neurons even after 3 months (when the mice become mature)
What conclusions from this figure can be made wrt the time course of adult neurogenesis?
No increase in neurogenesis after 6 months of age
Because there is no increase in neurogenesis after 6mos, what does this imply?
Neurogenesis is either stopping and neurons are maintained, or cells are dying and being replaced to maintain the pool
What is the objective of this figure?
Want to examine how ablation of adult neurogenesis affects the dentate gyrus
What are the key features of NSE:DTA that make it important for this paper?
NSA is only expressed in differentiated, post-mitotic neurons
CONDITIONAL CELL DEATH
NSA will have the stop codon cut out before it gets turned on, but will sit around waiting to activate DTA
At which point will this cell die
When NSE gets turned on in the last panel on the upper right
What is the purpose of BrdU?
Will track the number of new neurons generated after tamoxifen injection
Why is it important that the authors are only ablating neurons here and not the stem cells?
Because stem cells have the potential to become glial cells – this would introduce a confounding variable
What is happening in this image?
After DTA activation, there is decreased DTX (which marks newly-born, immature neurons) – indication that there are fewer new cells being born
What do these results show?
There is no gradual increase in mature (NeuN+) neurons as seen in the control
What do the results of this figure demonstrate?
The control mice “increase” (according to authors… sceptical)
no increase in neurogenesis in tamo mice
What issue could be confounding these results?
Might be some remaining stem cells that were not ablated (remember – nestin recombinase only affects 2/3 of cells) – these remaining cells might be working overtime to compensate for phyiological loss
The barnes maze test examines…
Spatial learning and memory
What conclusions can be made based on these barnes maze test results
Memory deficits were not observed 24h after the test, but there seems to be a deficit in long term memory
What did the authors observe happened to olfaction when these same experiments were performed on the SVZ?
Able to block new granule/periglom cells
No defect in olf discrimination tho!!!
Role of adult neurogenesis in olf bulb unclear
