Poly-A RNA profiling of Drosophila neural stem cells and tumor cells reveals genes involved in brain tumorigenesis.
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ABSTRACT:
ORGANISM(S): Drosophila melanogaster
PROVIDER: GSE87085 | GEO | 2018/03/04
REPOSITORIES: GEO
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Project description:The TRIM-NHL protein Brain tumor (Brat) acts as a tumor suppressor in the Drosophila brain, but how it suppresses tumor formation is not completely understood. Here, we combine temperature controlled brat RNAi with transcriptome analysis to identify the immediate brat targets in Drosophila neuroblasts. Besides the known target Deadpan (Dpn), our experiments identify the transcription factor Zelda (Zld) as a critical target of brat. Our data show that Zld is expressed in neuroblasts and required to allow re-expression of Dpn in transit amplifying intermediate neural progenitors. Upon neuroblast division, Brat is enriched in one daughter cell where its NHL domain directly binds to specific motifs in the 3’UTR of dpn and zld mRNA to mediate their degradation. In brat mutants, both Dpn and Zld continue to be expressed, but inhibition of either transcription factor prevents tumorigenesis. Our genetic and biochemical data indicate that Dpn inhibition requires higher Brat levels than Zld inhibition and suggest a model where stepwise post-transcriptional inhibition of distinct factors ensures sequential generation of fates in a stem cell lineage.
2017-11-28 | GSE104592 | GEO
Project description:Drosophila melanogaster neural stem cells (neuroblasts [NBs]) divide asymmetrically by differentially segregating protein determinants into their daughter cells. Although the machinery for asymmetric protein segregation is well understood, the events that reprogram one of the two daughter cells toward terminal differentiation are less clear. In this study, we use time-resolved transcriptional profiling to identify the earliest transcriptional differences between the daughter cells on their way toward distinct fates. By screening for coregulated protein complexes, we identify vacuolar-type H+–ATPase (v-ATPase) among the first and most significantly down-regulated complexes in differentiating daughter cells. We show that v-ATPase is essential for NB growth and persistent activity of the Notch signaling pathway. Our data suggest that v-ATPase and Notch form a regulatory loop that acts in multiple stem cell lineages both during nervous system development and in the adult gut. We provide a unique resource for investigating neural stem cell biology and demonstrate that cell fate changes can be induced by transcriptional regulation of basic, cell-essential pathways.
2018-06-27 | GSE104049 | GEO
Project description:The Drosophila TRIM-NHL protein Brain tumor (Brat) plays important roles during early embryogenesis, in cell fate decisions, during neurogenesis and in mature neurons. Brat is an RNA-binding protein and functions as translational repressor. However, which RNAs Brat regulates and how RNA-binding specificity is achieved, is unknown. Using RNA-Immunoprecipitation we identify Brat-bound mRNAs in Drosophila embryos and define a consensus binding motif. Microarrays were used to profile Brat-associated RNAs from fly embryos.
2015-11-13 | GSE71663 | GEO
Project description:Paper abstract: Stem cells have the remarkable ability to give rise to both self-renewing and differentiating daughter cells. Drosophila neural stem cells segregate cell-fate determinants from the self-renewing cell to the differentiating daughter at each division. Here, we show that one such determinant, the homeodomain transcription factor Prospero, regulates the choice between stem cell self-renewal and differentiation. We have identified the in vivo targets of Prospero throughout the entire genome. We show that Prospero represses genes required for self-renewal, such as stem cell fate genes and cell-cycle genes. Surprisingly, Prospero is also required to activate genes for terminal differentiation. We further show that in the absence of Prospero, differentiating daughters revert to a stem cell-like fate: they express markers of self-renewal, exhibit increased proliferation, and fail to differentiate. These results define a blueprint for the transition from stem cell self-renewal to terminal differentiation. 6 wildtype samples and 6 prospero mutant samples were hybridised to arrays against a commom reference sample (generated from whole embryo cDNA). The prospero samples were indirectly compared to the wildtype samples via the common reference. Half the wildtype and half of the prospero arrays were dye-swapped.
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Project description:Generating diverse neurons involves spatially distinct neural stem cells that show age dependent developmental fates. Drosophila neuroblasts produce long, diverse yet stereotyped series of distinct neurons, called lineages. We searched for novel temporal factors that could pattern such extended lineages by RNA-sequencing of specific neuroblasts at various developmental times. We found that two RNA-binding proteins, Imp and Syp, display opposing high-to-low and low-to-high temporal gradients with distinct dynamics in specific lineages. Manipulating Imp/Syp levels in mushroom body neuroblasts revealed opposing roles in the specification of early and late temporal fates, primarily via regulation of Chinmo translation. This study implicates the opposing Imp/Syp gradients as temporal morphogens that encode stem cell age and govern birth time-dependent offspring cell fate through post-transcriptional regulation of temporal dentity genes.
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Project description:After demyelinating insult, the neuronal progenitors of the adult mouse sub-ventricular zone (SVZ) called neuroblasts convert into oligodendrocytes that participate to the remyelination process. We use this rare example of spontaneous fate conversion to identify the molecular mechanisms governing these processes. Using single cell RNA-sequencing, we show that SVZ neuroblasts fate conversion proceeds directly, through formation of a non-proliferating transient cellular state co-expressing markers of both neuronal and oligodendrocyte identities. Transition between the two identities starts immediately after demyelination and occurs gradually, by a stepwise upregulation/downregulation of key TFs and chromatin modifiers. Each step of this fate conversion involves fine adjustments of the transcription and translation machineries as well as tight regulation of metabolism and migratory behaviors. Together, these data constitute the first in-depth analysis of a spontaneous direct cell fate conversion in the adult mammalian CNS.
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Project description:Paper abstract: Stem cells have the remarkable ability to give rise to both self-renewing and differentiating daughter cells. Drosophila neural stem cells segregate cell-fate determinants from the self-renewing cell to the differentiating daughter at each division. Here, we show that one such determinant, the homeodomain transcription factor Prospero, regulates the choice between stem cell self-renewal and differentiation. We have identified the in vivo targets of Prospero throughout the entire genome. We show that Prospero represses genes required for self-renewal, such as stem cell fate genes and cell-cycle genes. Surprisingly, Prospero is also required to activate genes for terminal differentiation. We further show that in the absence of Prospero, differentiating daughters revert to a stem cell-like fate: they express markers of self-renewal, exhibit increased proliferation, and fail to differentiate. These results define a blueprint for the transition from stem cell self-renewal to terminal differentiation.
2009-10-01 | GSE18213 | GEO
Project description:Drosophila neuroblasts have emerged as a model for stem cell biology that is ideal for genetic analysis but is limited by the lack of cell-type specific gene expression data. Here, we describe a methodology to isolate large numbers of pure neuroblasts and differentiating neurons that retain both cell cycle and lineage characteristics. We determine transcriptional profiles by mRNA sequencing and identify 28 predicted neuroblast specific transcription factors, which can be arranged in a network containing hubs for Notch signaling, growth control and chromatin regulation. Overexpression and RNAi for these factors identify Klumpfuss as a regulator of self-renewal. We show that loss of Klu function causes premature differentiation while overexpression results in the formation of transplantable brain tumors. Our data represent a valuable resource for Drosophila developmental neurobiology and we describes methodology that can be applied to other invertebrate stem cell lineages as well. comparison of transcriptomes of Drosophila melanogaster larval neuroblasts and their differentiated daughter cells (neurons)
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Project description:During development, neural stem cells are temporally patterned to sequentially generate a variety of neural types before exiting the cell cycle. Temporal patterning is well-studied in Drosophila, where neural stem cells called neuroblasts sequentially express cascades of Temporal Transcription Factors (TTFs) to control the birth-order dependent neural specification. However, currently known TTFs were mostly identified through candidate antibody screening and may not be complete. In addition, many fundamental questions remain concerning the TTF cascade initiation, progression, and termination. It is also not known why temporal progression only happens in neuroblasts but not in their differentiated progeny. In this work, we performed single-cell RNA sequencing of Drosophila medulla neuroblasts of all ages to study the temporal patterning process with single-cell resolution. Our scRNA-seq data revealed that sets of genes involved in different biological processes show high to low or low to high gradients as neuroblasts age. We also identified a list of novel TTFs, and experimentally characterized their roles in the temporal progression and neural fate specification. Our study revealed a comprehensive temporal gene network that patterns medulla neuroblasts from start to end. Furthermore, we found that the progression and termination of this temporal cascade also require transcription factors differentially expressed along the differentiation axis (neuroblasts -> -> neurons). Lola proteins function as a speed modulator of temporal progression in neuroblasts; while Nerfin-1, a factor required to suppress de-differentiation in post-mitotic neurons, acts at the final temporal stage together with the last TTF of the cascade, to promote the switch to gliogenesis and the cell cycle exit. Our comprehensive study of the medulla neuroblast temporal cascade illustrated mechanisms that might be conserved in the temporal patterning of neural stem cells.
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Project description:One neural stem cell can produce multiple transiently amplifying, intermediate neural progenitors (INP), which collectively yield diverse neuronal types. It is unclear if and how serially derived INPs contribute to neuron fate diversification. Drosophila type II neuroblasts, like mammalian neural stem cells, deposit neurons and also glia through INPs. The consecutively born INPs in a given lineage produce morphologically distinct progeny, presumably due to their inheritance of different temporal factors from the INP-producing progenitor. To uncover the underlying temporal fating mechanisms, we profiled type II neuroblasts' transcriptome across time. Our results reveal opposing temporal gradients of Imp and Syp RNA-binding proteins (descending and ascending, respectively). Maintaining high Imp throughout serial INP production expands the number of neurons/glia with early temporal fate at the expense of cells with late fate. Conversely, precocious upregulation of Syp reduces the number of cells with early fate. Further, we reveal that the transcription factor, Seven-up initiates progression of the Imp/Syp gradients. Interestingly, neuroblasts apparently locked in their beginning Imp/Syp levels can still yield progeny with a small range of early fates. We propose that the Seven-up-initiated Imp/Syp gradients create coarse temporal windows within type II neuroblasts to pattern INPs, which subsequently undergo fine-tuned subtemporal patterning.
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