Project description:A brain consists of numerous distinct neurons arising from a limited number of progenitors, called neuroblasts in Drosophila. Each neuroblast makes a specific neuronal lineage. To unravel the transcriptional networks that underlie the development of distinct neuroblast lineages, we marked and isolated lineage-specific neuroblasts for RNA sequencing. We labeled particular neuroblasts throughout neurogenesis by activating a conditional neuroblast driver in specific lineages using various intersection strategies. The targeted neuroblasts were efficiently recovered using a custom-built device for robotic single cell picking. Transcriptome analysis on the mushroom body, antennal lobe, and type II neuroblasts besides non-selective neuroblasts, neurons, and glia revealed a rich repertoire of transcription factors expressed among neuroblasts in diverse patterns. In addition to those likely pan-neuroblast transcription factors, there exist many transcription factors selectively enriched or repressed in certain neuroblasts. The unique combinations of transcription factors present in different neuroblasts may govern the diverse lineage-specific neuron fates
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)
Project description:We profiled the transcriptome of Drosophila melanogaster embryos in ttk2D50 embryos or after over-expression using btl-GAL4; UAS-ttk, respectively. We further isolated cells that express btl-enh-RFPmoe (Cabernard and Affolter 2005) and FACS sorting, and profiled their transcriptomes in the same genetic backgrounds.
Project description:Members of the SWI/SNF chromatin-remodeling complex are among the most frequently mutated genes in human cancer. SWI/SNF complex controls self-renewal and differentiation in stem cell lineages but how this function relates to tumorigenesis is currently unclear. Here, we use Drosophila neuroblasts to demonstrate that the SWI/SNF component Osa (ARID1) prevents tumorigenesis in stem cell lineages by ensuring correct unidirectional lineage progression. Our transcriptome anaysis identifies Ham as a key Osa target gene. comparison of transcriptomes of wild type Drosophila melanogaster larval type II NB lineages (excluding neurons) and osa RNAi type II lineages containing mainly NB-like cells and INPs
Project description:To identify downstream genes which was regulated by maternal Ovo-B in PGCs, we compared the transcriptomes between OvoA-expressing PGCs and control PGCs by microarry analysis in Drosophila melanogaster. We used fluorescence-activated cell sorting (FACS) to isolate PGCs from the stage 16 embryos carrying the transgene, EGFP-vasa, which expresses GFP specifically and continuously in the germline throughout the life cycle.
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.
Project description:Cell-type specific transcriptional profiling is key to understanding cell fate specification and function. In order to achieve this it has been necessary, to date, to isolate specific cell types from complex tissues. We have developed 'TaDa', a technique that enables cell-specific profiling without cell isolation. TaDa permits genome-wide profiling of DNA- or chromatin-binding proteins without cell sorting, fixation or affinity purification. The method is simple, sensitive, highly reproducible and is in principle transferable to any model system. Here we show that TaDa can be used to identify transcribed genes in a cell-type specific manner. We profile the genome-wide binding of RNA polymerase II (Pol II) in adjacent, clonally related neural stem cells in intact Drosophila brains. Our data reveal the activity of non-canonical metabolic pathways in proliferating neuroepithelial cells, and highlight a possible role for the retinal determination gene regulatory network in patterning neural stem cell fates. We also identify temporal differences in the activity of signalling pathways that control neuroepithelial cell fate by profiling Pol II occupancy at two different stages of brain development. Using RNA Pol II TaDa to profile, in a cell-type specific manner, the transcriptional state of neuroepithelial cells at two stages of larval brain development. Closely related asymmetrically dividing neural stem cells (neuroblasts) were also profiled, in order to compare the transcriptomes of two different types of neural stem cells. 3 biological relicates were performed for 3rd instar neuroepithelial cells (with one dye-swap). 2 biological relicates were performed for 3rd instar neuroblasts (with dye-swap). 2 biological relicates were performed for 1st instar neuroepithelial cells (with dye-swap). As additional supporting evidence for the Pol II TaDa technique, 2 biological relicates were performed for 3rd instar salivary glands (with dye-swap) in order to compare with previous Pol II-ChIP data for this tissue [PMID 22821985].
Project description:Embryonic development results in the production of distinct tissue types, and different cell types within each tissue. A major goal of developmental biology is to uncover the “parts list” of cell types that comprise each organ. Here we perform single cell RNA sequencing (scRNA-seq) of the Drosophila embryo to identify the genes that characterize different cell and tissue types during development. We assay three different timepoints, revealing a coordinated change in gene expression within each tissue. Interestingly, we find that the elav and mhc genes, whose protein products are widely used as markers for neurons and muscles, respectively, show broad pan-embryonic expression, indicating the importance of post-transcriptional regulation. We next focus on the central nervous system (CNS), where we identify genes characterizing each stage of neuronal differentiation: from neural progenitors, called neuroblasts, to their immediate progeny ganglion mother cells (GMCs), followed by new-born neurons, young neurons, and the most mature neurons. Finally, we ask whether the clonal progeny of a single neuroblast (NB7-1) share a similar transcriptional identity. Surprisingly, we find that clonal identity does not lead to transcriptional clustering, showing that neurons within a lineage are diverse, and that neurons with a similar transcriptional profile (e.g. motor neurons, glia) are distributed among multiple neuroblast lineages. Although each lineage consists of diverse progeny, we were able to identify a previously uncharacterized gene, Fer3, as an excellent marker for the NB7-1 lineage. Within the NB7-1 lineage, transcriptional clusters are identifiable in neuroblasts and neurons, and each cluster is composed of current temporal transcription factor (e.g. Hunchback, Kruppel, Pdm, and Castor), novel temporal factors, and/or targets of the temporal transcription factors. In conclusion, we have characterized the embryonic transcriptome for all major tissue types and for three stages of development, as well as the first transcriptomic analysis of a single, identified neuroblast lineage, finding a lineage-enriched transcription factor.
Project description:We profiled the transcriptome of Drosophila melanogaster embryos in ttk2D50 embryos or after over-expression using btl-GAL4; UAS-ttk, respectively. We further isolated cells that express btl-enh-RFPmoe (Cabernard and Affolter 2005) and FACS sorting, and profiled their transcriptomes in the same genetic backgrounds. A total of 19 samples were analysed with 2-3 replicates each. For each embryos and sorted cells, the genotypes were: ttk2D50 btl-enh-RFPmoe (mutant; embryos: 2, cells: 2), btl-enh-RFPmoe (mutant control; embryos: 2, cells: 3), btl-GAL4; UAS-ttk, btl-enh-RFPmoe (over-expression; embryos: 3, cells: 2), btl-GAL4; btl-enh-RFPmoe (over-expression control; embryos: 3, cells: 2).