scholarly journals Rala and the exocyst control Pvr trafficking and signaling to ensure lymph gland homeostasis in Drosophila melanogaster

2020 ◽  
Author(s):  
Helene Knævelsrud ◽  
Caroline Baril ◽  
Gwenaëlle Gavory ◽  
Jorrit M. Enserink ◽  
Marc Therrien
Keyword(s):  
Receptor Tyrosine Kinase ◽  
Membrane Trafficking ◽  
Lymph Gland ◽  
Small Gtpase ◽  
Loss Of Function ◽  
Hematopoietic Progenitors ◽  
Hematopoietic Organ ◽  
Differentiated Cells ◽  
Epistasis Analysis ◽  
Guanine Exchange Factor

AbstractThe balance between hematopoietic progenitors and differentiated hemocytes is finely tuned during development. In the larval hematopoietic organ of Drosophila, called the lymph gland, the receptor tyrosine kinase Pvr signals from differentiated cells to maintain a pool of undifferentiated progenitors. However, little is known about the processes that support Pvr function. The small GTPase Ral is involved in the regulation of several membrane trafficking events. Drosophila has a single Ral protein, Rala, which has been implicated in the development of various tissues. Here, we investigated the involvement of Rala in the larval fly hematopoietic system. We discovered that the loss of Rala activity phenocopies Pvr loss of function by promoting hemocyte progenitor differentiation. Moreover, using epistasis analysis, we found that the guanine exchange factor RalGPS lies upstream of Rala in this event, whereas the exocyst and Rab11 are acting downstream. Strikingly, the loss of Rala activity leads to a considerable accumulation of Pvr at the plasma membrane, hence suggesting a trafficking defect and reduced Pvr function. Consistent with this hypothesis, Rala loss of function phenotype in the lymph gland is fully suppressed by constitutive STAT activity, which normally mediates Pvr function in the lymph gland. Together, our findings unravel a novel RalGPS-Rala-exocyst-Rab11 axis for the maintenance of lymph gland homeostasis through Pvr.

scholarly journals Drosophila as a Model to Study Cellular Communication Between the Hematopoietic Niche and Blood Progenitors Under Homeostatic Conditions and in Response to an Immune Stress

2021 ◽  
Vol 12 ◽  
Author(s):  
Ismaël Morin-Poulard ◽  
Yushun Tian ◽  
Nathalie Vanzo ◽  
Michèle Crozatier
Keyword(s):  
Blood Cell ◽  
Progenitor Cells ◽  
Blood Cells ◽  
Molecular Mechanisms ◽  
Vascular System ◽  
Lymph Gland ◽  
Hematopoietic Progenitors ◽  
Hematopoietic Stem ◽  
Hematopoietic Organ ◽  
Immune Stress

In adult mammals, blood cells are formed from hematopoietic stem progenitor cells, which are controlled by a complex cellular microenvironment called “niche”. Drosophila melanogaster is a powerful model organism to decipher the mechanisms controlling hematopoiesis, due both to its limited number of blood cell lineages and to the conservation of genes and signaling pathways throughout bilaterian evolution. Insect blood cells or hemocytes are similar to the mammalian myeloid lineage that ensures innate immunity functions. Like in vertebrates, two waves of hematopoiesis occur in Drosophila. The first wave takes place during embryogenesis. The second wave occurs at larval stages, where two distinct hematopoietic sites are identified: subcuticular hematopoietic pockets and a specialized hematopoietic organ called the lymph gland. In both sites, hematopoiesis is regulated by distinct niches. In hematopoietic pockets, sensory neurons of the peripheral nervous system provide a microenvironment that promotes embryonic hemocyte expansion and differentiation. In the lymph gland blood cells are produced from hematopoietic progenitors. A small cluster of cells called Posterior Signaling Centre (PSC) and the vascular system, along which the lymph gland develops, act collectively as a niche, under homeostatic conditions, to control the balance between maintenance and differentiation of lymph gland progenitors. In response to an immune stress such as wasp parasitism, lymph gland hematopoiesis is drastically modified and shifts towards emergency hematopoiesis, leading to increased progenitor proliferation and their differentiation into lamellocyte, a specific blood cell type which will neutralize the parasite. The PSC is essential to control this emergency response. In this review, we summarize Drosophila cellular and molecular mechanisms involved in the communication between the niche and hematopoietic progenitors, both under homeostatic and stress conditions. Finally, we discuss similarities between mechanisms by which niches regulate hematopoietic stem/progenitor cells in Drosophila and mammals.

scholarly journals Dual role for Jumu in the control of hematopoietic progenitors in the Drosophila lymph gland

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Yangguang Hao ◽  
Li Hua Jin
Keyword(s):  
Cell Fate ◽  
Progenitor Cell ◽  
Lymph Gland ◽  
Hematopoietic Progenitor Cell ◽  
Hematopoietic Progenitors ◽  
Hematopoietic Progenitor ◽  
Hematopoietic Organ ◽  
Intrinsic Factors ◽  
Toll Signaling ◽  
Signaling Center

The Drosophila lymph gland is a hematopoietic organ in which the maintenance of hematopoietic progenitor cell fate relies on intrinsic factors and extensive interaction with cells within a microenvironment. The posterior signaling center (PSC) is required for maintaining the balance between progenitors and their differentiation into mature hemocytes. Moreover, some factors from the progenitors cell-autonomously control blood cell differentiation. Here, we show that Jumeau (Jumu), a member of the forkhead (Fkh) transcription factor family, controls hemocyte differentiation of lymph gland through multiple regulatory mechanisms. Jumu maintains the proper differentiation of prohemocytes by cell-autonomously regulating the expression of Col in medullary zone and by non-cell-autonomously preventing the generation of expanded PSC cells. Jumu can also cell-autonomously control the proliferation of PSC cells through positive regulation of dMyc expression. We also show that a deficiency of jumu throughout the lymph gland can induce the differentiation of lamellocytes via activating Toll signaling.

scholarly journals Arf6 regulates RhoB subcellular localization to control cancer cell invasion

2019 ◽  
Vol 218 (11) ◽  
pp. 3812-3826 ◽  
Author(s):  
Kossay Zaoui ◽  
Charles V. Rajadurai ◽  
Stéphanie Duhamel ◽  
Morag Park
Keyword(s):  
Receptor Tyrosine Kinase ◽  
Membrane Trafficking ◽  
Small Gtpase ◽  
Membrane Microdomains ◽  
Subcellular Targeting ◽  
Cytoskeletal Organization ◽  
Endosomal Membranes ◽  
Strict Requirement ◽  
3D Cell Migration ◽  
Adp Ribosylation Factor

The ADP-ribosylation factor 6 (Arf6) is a small GTPase that regulates endocytic recycling processes in concert with various effectors. Arf6 controls cytoskeletal organization and membrane trafficking; however, the detailed mechanisms of regulation remain poorly understood. Here, we report that Arf6 forms a complex with RhoB. The interaction between RhoB and Arf6 is mediated by the GCI (glycine, cysteine, and isoleucine) residues (188–190) of RhoB. Specific targeting of Arf6 to plasma membrane or mitochondrial membranes promotes recruitment and colocalization of RhoB to these membrane microdomains. Arf6 depletion promotes the loss of RhoB from endosomal membranes and leads to RhoB degradation through an endolysosomal pathway. This results in defective actin and focal adhesion dynamics and increased 3D cell migration upon activation of the Met receptor tyrosine kinase. Our findings identify a novel regulatory mechanism for RhoB localization and stability by Arf6 and establish the strict requirement of Arf6 for RhoB-specific subcellular targeting to endosomes and biological functions.

scholarly journals Chk2-p53 and JNK in irradiation-induced cell death of hematopoietic progenitors and differentiated cells in Drosophila larval lymph gland

Biology Open ◽  
2021 ◽  
Author(s):  
Tram Thi Ngoc Nguyen ◽  
Jiwon Shim ◽  
Young-Han Song
Keyword(s):  
Dna Damage ◽  
Cell Death ◽  
Environmental Changes ◽  
Apoptotic Cell ◽  
Lymph Gland ◽  
Apoptotic Cell Death ◽  
Dna Double Strand Breaks ◽  
Hematopoietic Organ ◽  
Cell Death Pathways ◽  
Differentiated Cells

Ionizing radiation (IR) induces DNA double-strand breaks that activate the DNA damage response (DDR), which leads to cell cycle arrest, senescence, or apoptotic cell death. Understanding the DDR of stem cells is critical to tissue homeostasis and the survival of the organism. Drosophila hematopoiesis serves as a model system for sensing stress and environmental changes; however, their response to DNA damage remains largely unexplored. The Drosophila lymph gland is the larval hematopoietic organ, where stem-like progenitors proliferate and differentiate into mature blood cells called hemocytes. We found that apoptotic cell death was induced in progenitors and hemocytes after 40 Gy irradiation, with progenitors showing more resistance to IR-induced cell death compared to hemocytes at a lower dose. Furthermore, we found that Drosophila ATM (tefu), Chk2 (lok), p53, and reaper were necessary for IR-induced cell death in the progenitors. Notably, IR-induced cell death in mature hemocytes required tefu, Drosophila JNK (bsk), and reaper, but not lok or p53. In summary, we found that DNA damage induces apoptotic cell death in the late third instar larval lymph gland and identified lok/p53-dependent and -independent cell death pathways in progenitors and mature hemocytes, respectively.

scholarly journals Novel and Converging Ways of NOX2 and SOD3 in Trafficking and Redox Signaling in Macrophages

Antioxidants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 172
Author(s):  
Steen Vang Petersen ◽  
Nanna Bach Poulsen ◽  
Cecilie Linneberg Matthiesen ◽  
Frederik Vilhardt
Keyword(s):  
Hydrogen Peroxide ◽  
Membrane Trafficking ◽  
Spatial Organization ◽  
Redox Signaling ◽  
Small Gtpase ◽  
Paracrine Signaling ◽  
Tissue Macrophage ◽  
Storage Vesicles ◽  
Superoxide Dismutase 3 ◽  
Macrophage Populations

Macrophages and related tissue macrophage populations use the classical NADPH oxidase (NOX2) for the regulated production of superoxide and derived oxidants for pathogen combat and redox signaling. With an emphasis on macrophages, we discuss how sorting into secretory storage vesicles, agonist-responsive membrane trafficking, and segregation into sphingolipid and cholesterol-enriched microdomains (lipid rafts) determine the subcellular distribution and spatial organization of NOX2 and superoxide dismutase-3 (SOD3). We discuss how inflammatory activation of macrophages, in part through small GTPase Rab27A/B regulation of the secretory compartments, mediates the coalescence of these two proteins on the cell surface to deliver a focalized hydrogen peroxide output. In interplay with membrane-embedded oxidant transporters and redox sensitive target proteins, this arrangement allows for the autocrine and paracrine signaling, which govern macrophage activation states and transcriptional programs. By discussing examples of autocrine and paracrine redox signaling, we highlight why formation of spatiotemporal microenvironments where produced superoxide is rapidly converted to hydrogen peroxide and conveyed immediately to reach redox targets in proximal vicinity is required for efficient redox signaling. Finally, we discuss the recent discovery of macrophage-derived exosomes as vehicles of NOX2 holoenzyme export to other cells.

scholarly journals miR-16-5p Promotes Erythroid Maturation of Erythroleukemia Cells by Regulating Ribosome Biogenesis

2021 ◽  
Vol 14 (2) ◽  
pp. 137
Author(s):  
Christos I. Papagiannopoulos ◽  
Nikoleta F. Theodoroula ◽  
Ioannis S. Vizirianakis
Keyword(s):  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Cultured Cells ◽  
Erythroid Differentiation ◽  
Underlying Mechanism ◽  
Loss Of Function ◽  
Functional Studies ◽  
Differentiated Cells ◽  
Erythroleukemia Cells ◽  
Murine Erythroleukemia

miRNAs constitute a class of non-coding RNA that act as powerful epigenetic regulators in animal and plant cells. In order to identify putative tumor-suppressor miRNAs we profiled the expression of various miRNAs during differentiation of erythroleukemia cells. RNA was purified before and after differentiation induction and subjected to quantitative RT-PCR. The majority of the miRNAs tested were found upregulated in differentiated cells with miR-16-5p showing the most significant increase. Functional studies using gain- and loss-of-function constructs proposed that miR-16-5p has a role in promoting the erythroid differentiation program of murine erythroleukemia (MEL) cells. In order to identify the underlying mechanism of action, we utilized bioinformatic in-silico platforms that incorporate predictions for the genes targeted by miR-16-5p. Interestingly, ribosome constituents, as well as ribosome biogenesis factors, were overrepresented among the miR-16-5p predicted gene targets. Accordingly, biochemical experiments showed that, indeed, miR-16-5p could modulate the levels of independent ribosomal proteins, and the overall ribosomal levels in cultured cells. In conclusion, miR-16-5p is identified as a differentiation-promoting agent in erythroleukemia cells, demonstrating antiproliferative activity, likely as a result of its ability to target the ribosomal machinery and restore any imbalanced activity imposed by the malignancy and the blockade of differentiation.

Pax-2 is required for mesenchyme-to-epithelium conversion during kidney development

Development ◽  
1993 ◽  
Vol 119 (3) ◽  
pp. 711-720 ◽  
Author(s):  
U. W. Rothenpieler ◽  
G. R. Dressler
Keyword(s):  
Kidney Development ◽  
Morphological Changes ◽  
Cell Formation ◽  
Protein Accumulation ◽  
Metanephric Mesenchyme ◽  
Loss Of Function ◽  
Organ Cultures ◽  
Protein Levels ◽  
Differentiated Cells ◽  
Mesenchyme Cells

The conversion of mesenchyme to epithelium during the embryonic development of the mammalian kidney requires reciprocal inductive interactions between the ureter and the responding metanephric mesenchyme. The Pax-2 gene is activated in the mesenchyme in response to induction and is subsequently down-regulated in more differentiated cells derived from the mesenchyme. Pax-2 belongs to a family of genes, at least three of which encode morphogenetic regulatory transcription factors. In order to determine the role of Pax-2 during kidney development, we have generated a loss- of-function phenotype using antisense oligonucleotides in mouse kidney organ cultures. These oligonucleotides can specifically inhibit Pax-2 protein accumulation in kidney mesenchyme cells, where the intracellular concentrations are maximal. The kidney organ cultures were stained with uvomurulin and laminin antibodies as markers for epithelium formation. With significantly reduced Pax-2 protein levels, kidney mesenchyme cells fail to aggregate and do not undergo the sequential morphological changes characteristic of epithelial cell formation. The data demonstrate that Pax-2 function is required for the earliest phase of mesenchyme-to-epithelium conversion.

scholarly journals SOX2 is required independently in both stem and differentiated cells for pituitary tumorigenesis in p27 null mice

2020 ◽  
Author(s):  
Veronica Moncho-Amor ◽  
Probir Chakravarty ◽  
Christophe Galichet ◽  
Ander Matheu ◽  
Robin Lovell-Badge ◽  
...  
Keyword(s):  
Mapk Pathway ◽  
Regulatory Region ◽  
Lineage Tracing ◽  
Intermediate Lobe ◽  
Loss Of Function ◽  
Cellular Origin ◽  
Differentiated Cells ◽  
Pituitary Tumorigenesis ◽  
Cellular Context ◽  
Pituitary Intermediate Lobe

AbstractLoss of P27 predominantly results in development of murine pituitary intermediate lobe (IL) tumours. We previously showed that the pleiotropic protein P27 can drive repression of the transcription factor Sox2. This interaction plays an important role during development of p27-/- IL tumours because loss of one copy of Sox2 diminishes tumorigenesis. Here, we have explored the cellular origin and mechanisms underlying melanotroph tumorigenesis in p27-/- IL. We show that IL hyperplasia is associated with reduced cellular differentiation, while levels of SOX2 increase in both stem cells (SC) and melanotrophs. Using loss-of-function and lineage tracing approaches, we demonstrate that SOX2 is required cell-autonomously in p27-/- melanotrophs and SCs for tumorigenesis. This is supported by studies deleting the Sox2 regulatory region 2 (Srr2), which is the target of P27 repressive action. Single cell transcriptomic analysis reveals that activation of a SOX2-dependent MAPK pathway in SCs is important for p27-/- tumorigenesis. Our data highlight different roles of SOX2 following loss of p27, according to the cellular context. Furthermore, we uncover a tumor-promoting function for SCs, which is SOX2-dependant. In conclusion, our results imply that targeting SCs, in addition to tumour cells themselves, may represent an efficient anti-tumoral strategy in certain contexts.

scholarly journals A parasitoid wasp of Drosophila employs preemptive and reactive strategies to deplete its host’s blood cells

2021 ◽  
Author(s):  
Johnny R. Ramroop ◽  
Mary Ellen Heavner ◽  
Zubaidul H. Razzak ◽  
Shubha Govind
Keyword(s):  
Extracellular Vesicles ◽  
Cellular Immunity ◽  
Blood Cells ◽  
Insect Pests ◽  
Lymph Gland ◽  
Parasite Development ◽  
Parasitoid Wasps ◽  
Parasitic Wasps ◽  
Hematopoietic Organ ◽  
Leptopilina Heterotoma

AbstractThe wasps Leptopilina heterotoma parasitize and ingest their Drosophila hosts. They produce extracellular vesicles (EVs) in the venom that are packed with proteins, some of which perform immune suppressive functions. EV interactions with blood cells of host larvae are linked to hematopoietic depletion, immune suppression, and parasite success. But how EVs disperse within the host, enter and kill hematopoietic cells are not well understood. Using an antibody marker for L. heterotoma EVs, we show that these parasite-derived structures are readily distributed within the hosts’ hemolymphatic system. EVs converge around the tightly clustered cells of the posterior signaling center (PSC) of the larval lymph gland, a small hematopoietic organ in Drosophila. The PSC serves as a source of developmental signals in naïve animals. In wasp-infected animals, the PSC directs the differentiation of lymph gland progenitors into lamellocytes. These lamellocytes are needed to encapsulate the wasp egg and block parasite development. We found that L. heterotoma infection disassembles the PSC and PSC cells disperse into the disintegrating lymph gland lobes. Genetically manipulated PSC-less lymph glands remain non-responsive and largely intact in the face of L. heterotoma infection. We also show that the larval lymph gland progenitors use the endocytic machinery to internalize EVs. Once inside, L. heterotoma EVs damage the Rab7- and LAMP1-positive late endocytic and phagolysosomal compartments. Rab5 maintains hematopoietic and immune quiescence as Rab5 knockdown results in hematopoietic over-proliferation and ectopic lamellocyte differentiation. Thus, both aspects of anti-parasite immunity, i.e., (a) phagocytosis of the wasp’s immune-suppressive EVs, and (b) progenitor differentiation for wasp egg encapsulation reside in the lymph gland. These results help explain why the lymph gland is specifically and precisely targeted for destruction. The parasite’s simultaneous and multipronged approach to block cellular immunity not only eliminates blood cells, but also tactically blocks the genetic programming needed for supplementary hematopoietic differentiation necessary for host success. In addition to its known functions in hematopoiesis, our results highlight a previously unrecognized phagocytic role of the lymph gland in cellular immunity. EV-mediated virulence strategies described for L. heterotoma are likely to be shared by other parasitoid wasps; their understanding can improve the design and development of novel therapeutics and biopesticides as well as help protect biodiversity.Author summaryParasitoid wasps serve as biological control agents of agricultural insect pests and are worthy of study. Many parasitic wasps develop inside their hosts to emerge as free-living adults. To overcome the resistance of their hosts, parasitic wasps use varied and ingenious strategies such as mimicry, evasion, bioactive venom, virus-like particles, viruses, and extracellular vesicles (EVs). We describe the effects of a unique class of EVs containing virulence proteins and produced in the venom of wasps that parasitize fruit flies of Drosophila species. EVs from Leptopilina heterotoma are widely distributed throughout the Drosophila hosts’ circulatory system after infection. They enter and kill macrophages by destroying the very same subcellular machinery that facilitates their uptake. An important protein in this process, Rab5, is needed to maintain the identity of the macrophage; when Rab5 function is reduced, macrophages turn into a different cell type called lamellocytes. Activities in the EVs can eliminate lamellocytes as well. EVs also interfere with the hosts’ genetic program that promotes lamellocyte differentiation needed to block parasite development. Thus, wasps combine specific preemptive and reactive strategies to deplete their hosts of the very cells that would otherwise sequester and kill them. These findings have applied value in agricultural pest control and medical therapeutics.

scholarly journals The pluripotent stem cell-specific transcript ESRG is dispensable for human pluripotency

2020 ◽  
Author(s):  
Kazutoshi Takahashi ◽  
Michiko Nakamura ◽  
Megumi Narita ◽  
Akira Watanabe ◽  
Mai Ueda ◽  
...  
Keyword(s):  
Global Gene Expression ◽  
Endogenous Retrovirus ◽  
Human Endogenous Retrovirus ◽  
Loss Of Function ◽  
Complete Excision ◽  
Differentiation Potential ◽  
Quantitative Expression ◽  
Differentiated Cells ◽  
Chimeric Transcripts ◽  
Non Coding Rnas

AbstractHuman pluripotent stem cells (PSCs) express human endogenous retrovirus type-H (HERV-H), which exists as more than a thousand copies on the human genome and frequently produces chimeric transcripts as long-non-coding RNAs (lncRNAs) fused with downstream neighbor genes. Previous studies showed that HERV-H expression is required for the maintenance of PSC identity, and aberrant HERV-H expression attenuates neural differentiation potentials, however, little is known about the actual of function of HERV-H. In this study, we focused on ESRG, which is known as a PSC-related HERV-H-driven lncRNA. The global transcriptome data of various tissues and cell lines and quantitative expression analysis of PSCs showed that ESRG expression is much higher than other HERV-Hs and tightly silenced after differentiation. However, the loss of function by the complete excision of the entire ESRG gene body using a CRISPR/Cas9 platform revealed that ESRG is dispensable for the maintenance of the primed and naïve pluripotent states. The loss of ESRG hardly affected the global gene expression of PSCs or the differentiation potential toward trilineage. Differentiated cells derived from ESRG-deficient PSCs retained the potential to be reprogrammed into induced PSCs (iPSCs) by the forced expression of OCT3/4, SOX2, and KLF4. In conclusion, ESRG is dispensable for the maintenance and recapturing of human pluripotency.

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