Cell cycle heterogeneity directs the timing of neural stem cell activation from quiescence

Otsuki, Leo; Brand, Andrea H.

doi:10.1126/science.aan8795

Cited by 143 publications

(162 citation statements)

References 42 publications

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“…However, quantification of cell cycle phases using a FUCCI-based reporter showed that NSCs depleted for NSC-TAFs or TRF2 were in fact primarily in G2 and exhibited hypersensitivity to manipulation of both the G1/S and G2/M transitions. This is intriguing because a recent study showed that quiescent NSCs, which are known to exhibit a primary process, arrest primarily in G2 and are labeled by tribbles (trbl), which encodes a conserved pseudokinase (50,51). These phenotypes are remarkably similar to those observed upon depletion of NSC-TAFs or TRF2 and we note that the trbl locus is occupied by TBP, TRF2S and TAF5.…”

Section: Cells (Escs) As Inducible Depletion Of Taf8 Resulted In Esc supporting

confidence: 67%

Distinct gene-selective roles for a network of core promoter factors inDrosophilaneural stem cell identity

Neves

Eisenman

2018

Preprint

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Running title: Role of core promoter factors in Drosophila neural stem cell identity. AbstractThe transcriptional mechanisms that allow neural stem cells (NSC) to balance selfrenewal with differentiation are not well understood. Employing an in vivo RNAi screen we identify here NSC-TAFs, a subset of nine TATA-binding protein associated factors (TAFs), as NSC identity genes in Drosophila. We found that depletion of NSC-TAFs results in decreased NSC clone size, reduced proliferation, defective cell polarity and increased hypersensitivity to cell cycle perturbation, without affecting NSC survival.Integrated gene expression and genomic binding analyses revealed that NSC-TAFs function with both TBP and TRF2, and that NSC-TAF-TBP and NSC-TAF-TRF2 shared target genes encode different subsets of transcription factors and RNA-binding proteins with established or emerging roles in NSC identity and brain development. Taken together, our results demonstrate that core promoter factors are selectively required for NSC identity in vivo by promoting cell cycle progression and NSC cell polarity as well as by restraining premature differentiation. Because pathogenic variants in a subset of TAFs have all been linked to human neurological disorders, this work may stimulate and inform future animal models of TAF-linked neurological disorders. Author summaryThe brains of many animal species are built with brain stem cells. Having too many brain stem cells can lead to brain tumors whereas too few can lead to birth defects such as microcephaly. A number of next generation sequencing studies have implicated proteins referred to as TATA-box-binding protein associated factors (TAFs) in human neurological disorders including microcephaly, but prior to this study, their function in brain development was unknown. Here we use brain stem cells, known as neural stem cells (NSCs), from the fruit fly Drosophila melanogaster as a model system to decipher how TAFs control brain stem cell identity. By combining genetics and low-input genomics, we show that TAFs directly control NSC cell division and cell polarity but do not appear to be required for NSC survival. We further show that TAFs accomplish these functions by associating either with their canonical partner TBP (TATA-binding protein) or the related protein TRF2. In summary, our study reveals unexpected and gene-selective functions of a unique subset of TAFs and their binding partners, which could inform future studies that seek to model human neurological disorders associated with TAFs. 0

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Section: Cells (Escs) As Inducible Depletion Of Taf8 Resulted In Esc supporting

confidence: 67%

Distinct gene-selective roles for a network of core promoter factors inDrosophilaneural stem cell identity

Neves

Eisenman

2018

Preprint

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“…Active stem cells such as intestinal stem cells and germline stem cells have been extensively studied in Drosophila. However, studies on Drosophila quiescent stem cells are just emerging (Boukhatmi and Bray, 2018;Chaturvedi et al, 2017;Otsuki and Brand, 2018).…”

Section: G0 and G2 Arrest Of Adult Drosophila Renal Stem Cellsmentioning

confidence: 99%

“…For instance, the majority of Drosophila neural stem cells become quiescent and are arrested in G2 phase for 24 h after embryogenesis (Otsuki and Brand, 2018). G2 arrest is essential to maintain postnatal muscle stem cells in zebrafish (Nguyen et al, 2017).…”

Section: G0 and G2 Arrest Of Adult Drosophila Renal Stem Cellsmentioning

confidence: 99%

An abundant quiescent stem cell population inDrosophilaMalpighian tubules protects principal cells from kidney stones

Wang

Spradling

2019

Preprint

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Adult Drosophila Malpighian tubules have low rates of cell turnover but are vulnerable to damage caused by stones, like their mammalian counterparts, kidneys. We show that Drosophila renal stem cells (RSCs) comprise a unique, unipotent regenerative compartment. RSCs respond only to loss of nearby principal cells (PCs), cells critical for maintaining ionic balance. Perhaps due to the large size of PCs they are outnumbered by RSCs, which replace each lost cell with multiple PCs of lower ploidy. RSCs share a developmental origin with highly active intestinal stem cells (ISCs), and like ISCs generate daughters by asymmetric Notch signaling, yet RSCs remain quiescent in the absence of damage. Nevertheless, the capacity for RSC-mediated repair extends the lifespan of flies carrying kidney stones. We propose that abundant, RSC-like stem cells exist in other tissues with low rates of turnover where they may have been mistaken for differentiated tissue cells.

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“…The three human Tribbles (TRIB) pseudokinases are homologues of the Drosophila melanogaster pseudokinase termed Tribbles, which controls ovarian border cell and neuronal stem cell physiology [12,13]. Tribbles, the human TRIB1, 2 and 3 orthologues, and the related pseudokinase STK40, all contain a catalytically-impaired pseudokinase domain.…”

Section: Introductionmentioning

confidence: 99%

Repurposing covalent EGFR/HER2 inhibitors for on-target degradation of human Tribbles 2 (TRIB2) pseudokinase

Foulkes

Byrne

Bailey

et al. 2018

Preprint

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ONE SENTENCE SUMMARY:A Tribbles 2 pseudokinase small molecule screen led to the identification of known EGFR/HER2 inhibitors that alter the stability of TRIB2 in vitro and lead to rapid on-target degradation of TRIB2 in human cancer cells. SHORT ABSTRACT: (150 words)Tribbles 2 (TRIB2) is a cancer-associated pseudokinase with a diverse interactome, including the AKT signaling module. Substantial evidence demonstrates that TRIB2 dysregulation is important in multiple human tumors. The non-canonical TRIB2 pseudokinase domain contains a unique cysteine rich region and interacts with a peptide motif in its own C-terminal tail. We demonstrate that TRIB2 is a target for previously described small molecule protein kinase 'inhibitors', which were originally designed to inhibit the catalytic domain of EGFR/HER2 tyrosine kinases. Using thermal-shift assays and drug repurposing, we classify ligands that stabilize or destabilize the TRIB2 pseudokinase domain. TRIB2 destabilizing agents, including the clinical inhibitor afatinib, lead to rapid and ontarget TRIB2 protein degradation in tumor cells, eliciting tractable effects on cell signaling and survival. Our data identifies leads for further development of TRIB2-degrading drugs and highlights 2 compound-induced TRIB2 downregulation, which might be mechanistically relevant for other catalytically-deficient (pseudo)kinases targeted by small molecules. FULL ABSTRACT: (232 words)A major challenge associated with biochemical and cellular analysis of pseudokinases is the lack of target-validated small molecule ligands with which to probe molecular function. Human Tribbles 2 (TRIB2) is a cancer-associated pseudokinase with a diverse interactome, which includes the canonical AKT signaling module. There is substantial evidence that human TRIB2 is a therapeutic target in both solid tumors and blood cancers. The non-canonical TRIB2 pseudokinase domain contains a unique cysteine-rich region and interacts with a peptide motif in its own C-terminal tail, which was previously shown to drive interaction with cellular E3 ubiquitin ligases. In this study we demonstrate that TRIB2 is a target for previously described small molecule protein kinase inhibitors, which were originally designed to inhibit the canonical catalytic domain of the tyrosine kinases EGFR/HER2.Using a thermal-shift assay, we discovered TRIB2 ligands within the Published Kinase Inhibitor Set (PKIS), and employed a drug repurposing approach to classify compounds that either stabilize or destabilize TRIB2 in vitro. Remarkably, TRIB2 destabilizing agents, including the clinical covalent drug afatinib, lead to rapid and on-target TRIB2 degradation in human cells, eliciting tractable effects on signaling and survival. Our data reveal the first drug-leads for development of TRIB2-degrading ligands, which will also be invaluable for unravelling the cellular mechanisms of TRIB2-based signaling. Our study highlights that small molecule-induced protein downregulation through drug 'off-targets' might be relevant for other inhibitors th...

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Cell cycle heterogeneity directs the timing of neural stem cell activation from quiescence

Cited by 143 publications

References 42 publications

Distinct gene-selective roles for a network of core promoter factors inDrosophilaneural stem cell identity

Distinct gene-selective roles for a network of core promoter factors inDrosophilaneural stem cell identity

An abundant quiescent stem cell population inDrosophilaMalpighian tubules protects principal cells from kidney stones

Repurposing covalent EGFR/HER2 inhibitors for on-target degradation of human Tribbles 2 (TRIB2) pseudokinase

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