Within the adult mammalian brain, Neural Stem Cell (NSC)s are maintained in
distinct neurogenic niches in a mostly quiescent state. Activation of quiescent
NSCs first requires re-entry into the cell cycle in order for the pool to proliferate
and eventually commit to a neural fate, giving rise to newborn neurons. The
canonical Retinoblastoma (Rb)-E2 Promoter Binding Factor (E2f) pathway is
not only key in overcoming the Gap 1 Phase (G1)/S-phase restriction, but novelly
appears to be involved in adult neurogenesis and NSC activation. I
hypothesized that activator transcription factors E2 Promoter Binding Factor 1
(E2f1) and E2 Promoter Binding Factor 3 (E2f3) are crucial for exit from a
quiescent state in adult NSCs. The contribution of the activator E2fs in this
transition was studied using a Nestin-driven Cre Recombinase-Estrogen
Receptor Tamoxifen-2 Ligand Binding Domain (Cre-ERT2) system to induce
targeted deletion of E2f1/3 within NSCs in adult mice. We show that loss of
E2f1/3 causes significant neurogenic defects, including pro-neural activation
and decreased pools of adult NSCs, that preferentially adopt a quiescent profile
in the subventricular zone. We employed this model to further isolate
subventricular zone-derived NSCs using a Rosa26:Yellow Fluorescent Protein
(YFP) reporter and subsequently analysed transcriptional profiles by RNA
sequencing. Loss of E2f1/3 shifts NSC transcriptomes towards one overlapping
with quiescent neural stem cell signatures (Codega et al., 2014; Basak et al.,
2018), further highlighting the requirement of these E2fs for initial activation.
A significant portion of these differentially expressed genes are putative E2f targets. Transcriptionally, major pathways involving cell metabolism, cellular
signaling, and neural development are perturbed without activator E2f
expression.
In effect, this combined approach based on in vivo data and bioinformatics
analyses offers a method of prospective identification of novel regulators of
adult neurogenesis that require the activator E2fs. Preliminary data suggests
that AT-Hook Transcription Factor (Akna) is one such target worth pursuing.
Cumulatively, this project describes a unique role for E2f1 and E2f3 during NSC
exit from quiescence and subsequent activation towards differentiation. As
ongoing maintenance of quiescent NSCs is a necessary prerequisite for lifelong
neurogenesis, conclusions from this study could determine the therapeutic
potential of targeting activator E2fs to combat the niche exhaustion associated
with aging, injury, and neurodegenerative diseases.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/44144 |
| Date | 11 October 2022 |
| Creators | O'Neil, Daniel |
| Contributors | Slack, Ruth |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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