Investigating the molecular mechanisms of Tis11 in neural stem cell quiescence and reactivation

About This Grant

Quiescence is an actively maintained state, characterized by a reversible, cell-cycle arrest. Quiescent neural stem cells are found during development and in the adult mammalian brain, reactivating in response to certain cures such as injury or exercise. The regulation of neural stem cell (NSC) quiescence maintains stem cell populations and provides opportunity for brain repair. On the other hand, quiescence can also be pathological, theorized to contribute to tumor therapy resistance and recurrence. Understanding the regulation of quiescence in stem cells is therefore crucial to understanding development, disease and can serve as a starting point for new regenerative therapies. In Drosophila, quiescent neural stem cells (qNSCs) enter quiescence and reactivate in response to the secretion of insulin-like peptides. The transcription factor Worniu (wor) is translated early during NSC reactivation, even though the transcript is detectable during quiescence, indicating post-transcriptional regulation. Using single cell transcriptomics, we have identified differentially expressed genes during quiescence and reactivation of NSCs. Tis11, an RNA-binding protein was found to involved in regulating NSC reactivation and mediated both the transcript and protein levels of wor. Knockdown of Tis11 causes precocious reactivation, while misexpression delays reactivation, indicating a role in quiescence regulation. However, the precise molecular mechanisms by which Tis11 regulates quiescence and reactivation in NSCs is not known. The main aims of this project are to elucidate the precise molecular mechanisms of Tis11 in the regulation of quiescence. As Tis11 protein is shuttled between the nucleus and cytoplasm, this project will investigate its post-transcriptional and transcriptional roles. Using RNA immunoprecipitation-sequencing and Targeted DamID, the mRNA and genome-wide targeting targets of Tis11 will be profiled. The binding of Tis11 to wor will also be tested via luciferase reporter assay. Finally, the interaction between Tis11 and insulin signaling in qNSC reactivation will be examined via epistasis experiments. Interestingly, Tis11 also has a role in the maintenance of quiescence in intestinal stem cells. This project will therefore identify a potentially conserved molecular mechanism of quiescence regulation for stem cells in different tissues. Furthermore, Tis11 may be a potential therapeutic target, enabling the regulation of reactivation of stem cells for rejuvenation therapy. On the other hand, Tis11 may also be a target of interest, whereby inhibiting its activity may prevent therapy-resistant quiescent cancer cells from persisting in tumors. This training project will be performed at the vibrant Regenerative Medicine Institute at the NYU Grossman School of Medicine. The candidate will be working in a collaborative, interdisciplinary environment. The candidate’s work will pre presented at both local and international conferences, to increase exposure and opportunities to network. Career development training will take the form of workshops and personalized mentoring, preparing the candidate for a career as an independent investigator.