Biology subjects

Ewen-Campen, B.

Publications and source records attributed to Ewen-Campen, B..

12 recordsLinked to original sources

bioRxiv2026

FlyAnatoView: Visualization of Drosophila Single-cell RNA-seq Datasets on Anatomographs

Single-cell RNA sequencing (scRNA-seq) is a powerful approach for measuring the transcriptomic landscape at single-cell resolution. However, while scRNA-seq data reveals what genes each cell expresses, they do not indicate where that cell was located within the tissue or organ, anatomically. We developed FlyAnatoView (https://www.flyrnai.org/tools/rna_seq_base/web/svg_files/), a resource that projects scRNA-seq data onto anatomical diagrams, restoring this missing spatial context.

bioinformatics↗

bioRxiv2025

The Drosophila proventriculus lacks stem cells but compensates for age-related cell loss via endoreplication-mediated cell growth

The Drosophila proventriculus is a bulb-shaped structure at the juncture of the foregut and the midgut, which plays important roles in ingestion, peritrophic membrane synthesis, and the immune response to oral pathogens. A previous study identified a population of cells in the proventriculus which incorporate bromodeoxyuridine (BrdU), a marker of DNA synthesis, and proposed that these cycling cells are multipotent stem cells that replace dying cells elsewhere in the tissue. Here, we re-investigate these cycling cells and find that they do not undergo mitosis, do not generate clonal lineages, and do not proliferate in response to tissue damage, and are therefore not stem cells. Instead, we find that these cells continually endocycle throughout the flys life, increasing their ploidy and size, while at the same time cells in this tissue are lost into the gut lumen as the fly ages. Functionally, these cells play a critical role in the synthesis of peritrophic membrane components, and we show that when endocycling in these cells is experimentally increased or decreased, there is a concomitant change in ploidy, tissue size, and peritrophic membrane synthesis. Further, we show that inhibition of endocycling makes flies more susceptible to orally infectious bacteria. Altogether, we show that continual endocycling of these cells is critical for maintaining tissue size and function in the face of cell loss due to aging or tissue damage.

genetics↗

bioRxiv2025

Divergence of germ cell-less roles in germ line development across insect species

During development, sexually reproducing animals must specify and maintain the germ line, the lineage of cells that gives rise to the next generation of animals. In the fruit fly Drosophila melanogaster, germ cell-less (gcl) is required for the formation of primordial germ cells in the form of cells that cellularize at the posterior pole of the embryo, called pole cells. Forming pole cells is a mechanism of germ cell formation unique to a subset of insects. Even though most animals do not form pole cells as primordial germ cells, gcl is conserved across Metazoa, raising the question of how this conserved gene acquired its central role in the evolutionarily derived process of pole cell formation. Here, we examine the functions of gcl in two other insects with different modes of germ cell specification: the milkweed bug Oncopeltus fasciatus and the cricket Gryllus bimaculatus. We found that gcl is involved in germ cell development, but not strictly required for germ cell specification, in O. fasciatus, although it appears to function through a mechanism different from that in D. melanogaster. In contrast, we could not detect any impact on the embryonic germ line upon gcl knockdown in G. bimaculatus. This work serves as a case study into how the roles of genes in the process of germ line development can change over evolutionary time across animals. HighlightsO_LIgerm cell-less knockout reduces germ cell number in Oncopeltus fasciatus. C_LIO_LIgerm cell-less knockdown does not affect germ cell number in Gryllus bimaculatus. C_LIO_LIThe genetic mechanisms through which gcl affects germ cell number have diverged among insects. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=75 SRC="FIGDIR/small/645619v2_ufig1.gif" ALT="Figure 1"> View larger version (11K): org.highwire.dtl.DTLVardef@16ce97aorg.highwire.dtl.DTLVardef@1544b5eorg.highwire.dtl.DTLVardef@120219forg.highwire.dtl.DTLVardef@7f588e_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2024

A collection of split-Gal4 drivers targeting conserved signaling ligands in Drosophila

Communication between cells in metazoan organisms is mediated by a remarkably small number of highly conserved signaling pathways. Given the relatively small number of signaling pathways, the existence of multiple related ligands for many of these pathways is thought to represent a key evolutionary innovation for encoding complexity into cell-cell signaling. Relatedly, crosstalk and other interactions between pathways is another critical feature which allows a modest number pathways to ultimately generate an enormously diverse range of outcomes. It would thus be useful to have genetic tools to identify and manipulate not only those cells which express a given signaling ligand, but also those cells that specifically co-express pairs of signaling ligands. Here, we present a collection of split-Gal4 knock-in lines targeting many of the ligands for highly conserved signaling pathways in Drosophila (Notch, Hedgehog, FGF, EGF, TGF{beta}, JAK/STAT, JNK, and PVR). We demonstrate that these lines faithfully recapitulate the endogenous expression pattern of their targets, and that they can be used to specifically identify the cells and tissues that co-express pairs of signaling ligands. As a proof of principle, we demonstrate that the 4th chromosome TGF{beta} ligands myoglianin and maverick are broadly co-expressed in muscles and other tissues of both larva and adults, and that the JAK/STAT ligands upd2 and upd3 are partially co-expressed from cells of the midgut following gut damage. Together with our previously collection of split-Gal4 lines targeting the seven Wnt ligands, this resource allows Drosophila researchers to identify and genetically manipulate cells that specifically express pairs of conserved ligands from nearly all the major intercellular signaling pathways.

genetics↗

bioRxiv2024

Wnt signaling modulates the response to DNA damage in the Drosophila wing imaginal disc by regulating the EGFR pathway

Despite the deep conservation of the DNA damage response pathway (DDR), cells in different contexts vary widely in their susceptibility to DNA damage and their propensity to undergo apoptosis as a result of genomic lesions. One of the cell signaling pathways implicated in modulating the DDR is the highly conserved Wnt pathway, which is known to promote resistance to DNA damage caused by ionizing radiation in a variety of human cancers. However, the mechanisms linking Wnt signal transduction to the DDR remain unclear. Here, we use a genetically encoded system in Drosophila to reliably induce consistent levels of DNA damage in vivo, and demonstrate that canonical Wnt signaling in the wing imaginal disc buffers cells against apoptosis in the face of DNA double-strand breaks. We show that Wg, the primary Wnt ligand in Drosophila, activates Epidermal Growth Factor Receptor (EGFR) signaling via the ligand-processing protease Rhomboid, which in turn modulates the DDR in a Chk2, p53, and E2F1-dependent manner. These studies provide mechanistic insight into the modulation of the DDR by the Wnt and EGFR pathways in vivo in a highly proliferative tissue. Furthermore, they reveal how the growth and patterning functions of Wnt signaling are coupled with pro-survival, anti-apoptotic activities, thereby facilitating developmental robustness in the face of genomic damage. Author SummaryEctopic activation of the highly conserved Wnt signaling pathway has been previously demonstrated to promote resistance to radiation and chemoradiation therapy in a variety of human cancers, yet the mechanisms by which Wnt modulates the DDR pathway are not clearly established. Furthermore, putative interactions between Wnt signaling and the DDR outside the context of pathological Wnt over-expressing tumors have not been clearly elucidated. Here, we show that, in Drosophila, loss of canonical Wnt signaling during development of the highly proliferative wing imaginal disc sensitizes cells to DNA damage, biasing them towards apoptosis and ultimately disrupting normal wing development. In contrast, ectopic Wnt signaling reduces the level of apoptosis for a given level of DNA damage. Mechanistically, we demonstrate that Wnt signaling acts via Epidermal Growth Factor Receptor (EGFR) signaling, a well characterized pro-survival pathway, by activating the ligand-processing protease Rhomboid, and that this effect requires core DDR components Chk2, p53, and E2F1. Altogether, we show that Wnt signaling can promote developmental robustness by opposing apoptosis in the face of DNA damage, and reveal a mechanism by which Wnt signaling modulates the DDR via EGFR signaling.

genetics↗

bioRxiv2023

Expanding the Drosophila toolkit for dual control of gene expression

The ability to independently control gene expression in two different tissues in the same animal is emerging as a major need, especially in the context of inter-organ communication studies. This type of study is made possible by technologies combining the GAL4/UAS and a second binary expression system such as the LexA-system or QF-system. Here, we describe a resource of reagents that facilitate combined use of the GAL4/UAS and a second binary system in various Drosophila tissues. Focusing on genes with well-characterizsed GAL4 expression patterns, we generated a set of more than 40 LexA-GAD and QF2 insertions by CRISPR knock-in and verified their tissue-specificity in larvae. We also built constructs that encode QF2 and LexA-GAD transcription factors in a single vector. Following successful integration of this construct into the fly genome, FLP/FRT recombination is used to isolate fly lines that express only QF2 or LexA-GAD. Finally, using new compatible shRNA vectors, we evaluated both LexA and QF systems for in vivo gene knockdown and are generating a library of such RNAi fly lines as a community resource. Together, these LexA and QF system vectors and fly lines will provide a new set of tools for researchers who need to activate or repress two different genes in an orthogonal manner in the same animal.

genetics↗

bioRxiv2023

Split-intein Gal4 provides intersectional genetic labeling that is fully repressible by Gal80

The split-Gal4 system allows for intersectional genetic labeling of highly specific cell-types and tissues in Drosophila. However, the existing split-Gal4 system, unlike the standard Gal4 system, cannot be repressed by Gal80, and therefore cannot be controlled temporally. This lack of temporal control precludes split-Gal4 experiments in which a genetic manipulation must be restricted to specific timepoints. Here, we describe a new split-Gal4 system based on a self-excising split-intein, which drives transgene expression as strongly as the current split-Gal4 system and Gal4 reagents, yet which is fully repressible by Gal80. We demonstrate the potent inducibility of "split-intein Gal4" in vivo using both fluorescent reporters and via reversible tumor induction in the gut. Further, we show that our split-intein Gal4 can be extended to the drug-inducible GeneSwitch system, providing an independent method for intersectional labeling with inducible control. We also show that the split-intein Gal4 system can be used to generate highly cell-type specific genetic drivers based on in silico predictions generated by single cell RNAseq (scRNAseq) datasets, and we describe a new algorithm ("Two Against Background" or TAB) to predict cluster-specific gene pairs across multiple tissue-specific scRNA datasets. We provide a plasmid toolkit to efficiently create split-intein Gal4 drivers based on either CRISPR knock-ins to target genes or using enhancer fragments. Altogether, the split-intein Gal4 system allows for the creation of highly specific intersectional genetic drivers that are inducible/repressible. Significance statementThe split-Gal4 system allows Drosophila researchers to drive transgene expression with extraordinary cell type specificity. However, the existing split-Gal4 system cannot be controlled temporally, and therefore cannot be applied to many important areas of research. Here, we present a new split-Gal4 system based on a self-excising split-intein, which is fully controllable by Gal80, as well as a related drug-inducible split GeneSwitch system. This approach can both leverage and inform single-cell RNAseq datasets, and we introduce an algorithm to identify pairs of genes that precisely and narrowly mark a desired cell cluster. Our split-intein Gal4 system will be of value to the Drosophila research community, and allow for the creation of highly specific genetic drivers that are also inducible/repressible.

genetics↗

bioRxiv2022

Paralog Explorer: a resource for mining information about paralogs in common research organisms

Paralogs are genes which arose via gene duplication, and when such paralogs retain overlapping or redundant function, this poses a challenge to functional genetics research. Recent technological advancements have made it possible to systematically probe gene function for redundant genes using dual or multiplex gene perturbation, and there is a need for a simple bioinformatic tool to identify putative paralogs of a gene(s) of interest. We have developed Paralog Explorer (https://www.flyrnai.org/tools/paralogs/), an online resource that allows researchers to quickly and accurately identify candidate paralogous genes in the genomes of the model organisms D. melanogaster, C. elegans, D. rerio, M. musculus, and H. sapiens. Paralog Explorer deploys an effective between-species ortholog prediction software, DIOPT, to analyze within-species paralogs. Paralog Explorer allows users to identify candidate paralogs, and to navigate relevant databases regarding gene co-expression, protein-protein and genetic interaction, as well as gene ontology and phenotype annotations. Altogether, this tool extends the value of current ortholog prediction resources by providing sophisticated features useful for identification and study of paralogous genes.

bioinformatics↗

bioRxiv2020

Wnt ligands are not required for planar cell polarity in the Drosophila wing or notum

The frizzled (fz) and disheveled (dsh) genes are highly conserved members of the core planar cell polarity (PCP) pathway and of the Wnt signaling pathway. Given these dual functions, a number of studies have examined whether Wnt ligands may provide a global, tissue-scale orientation cue for PCP establishment during development, and these studies have reached differing conclusions. In this study, we re-examine this issue in the Drosophila melanogaster wing and notum using split-Gal4 co-expression analysis, systematic pairwise and triple somatic CRISPR-based knock-outs and double RNAi experiments. Pairwise loss-of-function experiments targeting wg together with other Wnt genes does not produce PCP defects, neither via somatic CRISPR nor RNAi. In addition, somatic knock-out of evi (aka wntless), which is required for the secretion of all Wnt ligands expressed in these tissues, did not produce detectable PCP phenotypes. Altogether, we were unable to find support for the hypothesis that Wnt ligands contribute to PCP signaling in the Drosophila wing or notum.

genetics↗

bioRxiv2019

Large-scale transgenic Drosophila resource collections for loss- and gain-of-function studies

The Transgenic RNAi Project (TRiP), a Drosophila functional genomics platform at Harvard Medical School, was initiated in 2008 to generate and distribute a genome-scale collection of RNAi fly stocks. To date, the TRiP has generated >15,000 RNAi fly stocks. As this covers most Drosophila genes, we have largely transitioned to development of new resources based on CRISPR technology. Here, we present an update on our libraries of publicly available RNAi and CRISPR fly stocks, and focus on the TRiP-CRISPR overexpression (TRiP-OE) and TRiP-CRISPR knockout (TRiP-KO) collections. TRiP-OE stocks express sgRNAs targeting upstream of a gene transcription start site. Gene activation is triggered by co-expression of catalytically dead Cas9 (dCas9) fused to an activator domain, either VP64-p65-Rta (VPR) or Synergistic Activation Mediator (SAM). TRiP-KO stocks express one or two sgRNAs targeting the coding sequence of a gene or genes, allowing for generation of indels in both germline and somatic tissue. To date, we have generated more than 5,000 CRISPR-OE or -KO stocks for the community. These resources provide versatile, transformative tools for gene activation, gene repression, and genome engineering.

genetics↗

bioRxiv2018

ovoD co-selection: a method for enriching CRISPR/Cas9-edited alleles in Drosophila

Screening for successful CRISPR/Cas9 editing events remains a time consuming technical bottleneck in the field of Drosophila genome editing. This step can be particularly laborious for events that do not cause a visible phenotype, or those which occur at relatively low frequency. A promising strategy to enrich for desired CRISPR events is to co-select for an independent CRISPR event that produces an easily detectable phenotype. Here, we describe a simple negative co-selection strategy involving CRISPR-editing of a dominant female sterile allele, ovoD1. In this system (\"ovoD co-selection\"), the only functional germ cells in injected females are those that have been edited at the ovoD1 locus, and thus 100% of the offspring of these flies have undergone editing of at least one locus. We demonstrate that ovoD co-selection can be used to enrich for knock-out mutagenesis via nonhomologous end-joining (NHEJ), and for knock-in alleles via homology-directed repair (HDR). Altogether, our results demonstrate that ovoD co-selection reduces the amount of screening necessary to isolate desired CRISPR events in Drosophila.

genetics↗

bioRxiv2018

Next generation CRISPR/Cas9 transcriptional activation in Drosophila using flySAM

CRISPR/Cas9-based transcriptional activation (CRISPRa) has recently emerged as a powerful and scalable technique for systematic over-expression genetic analysis in Drosophila melanogaster. We present flySAM, a potent new tool for in vivo CRISPRa, which offers a major improvement over existing strategies in terms of effectiveness, scalability, and ease-of-use. flySAM outperforms existing in vivo CRISPRa strategies, and approximates phenotypes obtained using traditional Gal4-UAS over-expression. Further, because flySAM typically only requires a single sgRNA, it dramatically improves scalability. We use flySAM to demonstrate multiplexed CRISPRa, which has not been previously shown in vivo. In addition, we have simplified the experimental usage of flySAM by creating a single vector encoding both the UAS:Cas9-activator and the sgRNA, allowing for inducible CRISPRa in a single genetic cross. flySAM will thus replace previous CRISPRa strategies as the basis of our growing genome-wide transgenic over-expression resource, TRiP-OE.

genetics↗