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1.
Proc Natl Acad Sci U S A ; 120(18): e2217862120, 2023 05 02.
Article in English | MEDLINE | ID: mdl-37094122

ABSTRACT

Hematopoietic stem and progenitor cells maintain blood cell homeostasis by integrating various cues provided by specialized microenvironments or niches. Biomechanical forces are emerging as key regulators of hematopoiesis. Here, we report that mechanical stimuli provided by blood flow in the vascular niche control Drosophila hematopoiesis. In vascular niche cells, the mechanosensitive channel Piezo transduces mechanical forces through intracellular calcium upregulation, leading to Notch activation and repression of FGF ligand transcription, known to regulate hematopoietic progenitor maintenance. Our results provide insight into how the vascular niche integrates mechanical stimuli to regulate hematopoiesis.


Subject(s)
Drosophila Proteins , Drosophila , Animals , Drosophila/metabolism , Drosophila Proteins/metabolism , Hematopoiesis/physiology , Blood Cells , Stem Cells/metabolism , Stem Cell Niche , Ion Channels
2.
Front Cell Dev Biol ; 10: 834720, 2022.
Article in English | MEDLINE | ID: mdl-35237606

ABSTRACT

The Drosophila lymph gland is the larval hematopoietic organ and is aligned along the anterior part of the cardiovascular system, composed of cardiac cells, that form the cardiac tube and its associated pericardial cells or nephrocytes. By the end of embryogenesis the lymph gland is composed of a single pair of lobes. Two additional pairs of posterior lobes develop during larval development to contribute to the mature lymph gland. In this study we describe the ontogeny of lymph gland posterior lobes during larval development and identify the genetic basis of the process. By lineage tracing we show here that each posterior lobe originates from three embryonic pericardial cells, thus establishing a bivalent blood cell/nephrocyte potential for a subset of embryonic pericardial cells. The posterior lobes of L3 larvae posterior lobes are composed of heterogeneous blood progenitors and their diversity is progressively built during larval development. We further establish that in larvae, homeotic genes and the transcription factor Klf15 regulate the choice between blood cell and nephrocyte fates. Our data underline the sequential production of blood cell progenitors during larval development.

3.
Front Immunol ; 12: 719349, 2021.
Article in English | MEDLINE | ID: mdl-34484226

ABSTRACT

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.


Subject(s)
Cell Communication , Hematopoiesis , Hematopoietic Stem Cells/cytology , Hematopoietic Stem Cells/metabolism , Homeostasis , Stem Cell Niche , Stress, Physiological , Animals , Cellular Microenvironment , Drosophila , Hemocytes/cytology , Hemocytes/metabolism , Larva , Models, Biological , Neurons/cytology , Neurons/metabolism , Stem Cell Niche/immunology , Stress, Physiological/immunology
4.
Elife ; 102021 01 04.
Article in English | MEDLINE | ID: mdl-33395389

ABSTRACT

In adult mammals, hematopoiesis, the production of blood cells from hematopoietic stem and progenitor cells (HSPCs), is tightly regulated by extrinsic signals from the microenvironment called 'niche'. Bone marrow HSPCs are heterogeneous and controlled by both endosteal and vascular niches. The Drosophila hematopoietic lymph gland is located along the cardiac tube which corresponds to the vascular system. In the lymph gland, the niche called Posterior Signaling Center controls only a subset of the heterogeneous hematopoietic progenitor population indicating that additional signals are necessary. Here we report that the vascular system acts as a second niche to control lymph gland homeostasis. The FGF ligand Branchless produced by vascular cells activates the FGF pathway in hematopoietic progenitors. By regulating intracellular calcium levels, FGF signaling maintains progenitor pools and prevents blood cell differentiation. This study reveals that two niches contribute to the control ofDrosophila blood cell homeostasis through their differential regulation of progenitors.


Subject(s)
Drosophila/physiology , Fibroblast Growth Factors/metabolism , Hematopoiesis/physiology , Signal Transduction , Animals
5.
Elife ; 62017 11 01.
Article in English | MEDLINE | ID: mdl-29091025

ABSTRACT

Hematopoietic stem/progenitor cells in the adult mammalian bone marrow ensure blood cell renewal. Their cellular microenvironment, called 'niche', regulates hematopoiesis both under homeostatic and immune stress conditions. In the Drosophila hematopoietic organ, the lymph gland, the posterior signaling center (PSC) acts as a niche to regulate the hematopoietic response to immune stress such as wasp parasitism. This response relies on the differentiation of lamellocytes, a cryptic cell type, dedicated to pathogen encapsulation and killing. Here, we establish that Toll/NF-κB pathway activation in the PSC in response to wasp parasitism non-cell autonomously induces the lymph gland immune response. Our data further establish a regulatory network where co-activation of Toll/NF-κB and EGFR signaling by ROS levels in the PSC/niche controls lymph gland hematopoiesis under parasitism. Whether a similar regulatory network operates in mammals to control emergency hematopoiesis is an open question.


Subject(s)
Drosophila Proteins/metabolism , Drosophila/immunology , ErbB Receptors/metabolism , Hematopoiesis , NF-kappa B/metabolism , Reactive Oxygen Species/metabolism , Receptors, Invertebrate Peptide/metabolism , Toll-Like Receptors/metabolism , Wasps/immunology , Animals , Drosophila/parasitology , Host-Parasite Interactions , Immunity, Innate
6.
FEBS Lett ; 590(22): 4034-4051, 2016 Nov.
Article in English | MEDLINE | ID: mdl-27455465

ABSTRACT

The emergence of hematopoietic progenitors and their differentiation into various highly specialized blood cell types constitute a finely tuned process. Unveiling the genetic cascades that control blood cell progenitor fate and understanding how they are modulated in response to environmental changes are two major challenges in the field of hematopoiesis. In the last 20 years, many studies have established important functional analogies between blood cell development in vertebrates and in the fruit fly, Drosophila melanogaster. Thereby, Drosophila has emerged as a powerful genetic model for studying mechanisms that control hematopoiesis during normal development or in pathological situations. Moreover, recent advances in Drosophila have highlighted how intricate cell communication networks and microenvironmental cues regulate blood cell homeostasis. They have also revealed the striking plasticity of Drosophila mature blood cells and the presence of different sites of hematopoiesis in the larva. This review provides an overview of Drosophila hematopoiesis during development and summarizes our current knowledge on the molecular processes controlling larval hematopoiesis, both under normal conditions and in response to an immune challenge, such as wasp parasitism.


Subject(s)
Blood Cells/cytology , Drosophila melanogaster/genetics , Hematopoiesis/genetics , Hematopoietic Stem Cells , Animals , Cell Communication , Cell Differentiation/genetics , Cellular Microenvironment/genetics , Drosophila melanogaster/growth & development , Humans , Larva/genetics , Larva/growth & development
7.
Nat Commun ; 7: 11634, 2016 05 19.
Article in English | MEDLINE | ID: mdl-27193394

ABSTRACT

Self-renewal and differentiation of mammalian haematopoietic stem cells (HSCs) are controlled by a specialized microenvironment called 'the niche'. In the bone marrow, HSCs receive signals from both the endosteal and vascular niches. The posterior signalling centre (PSC) of the larval Drosophila haematopoietic organ, the lymph gland, regulates blood cell differentiation under normal conditions and also plays a key role in controlling haematopoiesis under immune challenge. Here we report that the Drosophila vascular system also contributes to the lymph gland homoeostasis. Vascular cells produce Slit that activates Robo receptors in the PSC. Robo activation controls proliferation and clustering of PSC cells by regulating Myc, and small GTPase and DE-cadherin activity, respectively. These findings reveal that signals from the vascular system contribute to regulating the rate of blood cell differentiation via the regulation of PSC morphology.


Subject(s)
Drosophila Proteins/metabolism , Drosophila/physiology , Hematopoiesis , Nerve Tissue Proteins/metabolism , Receptors, Immunologic/metabolism , Animals , Cadherins/metabolism , Cardiovascular System/metabolism , Drosophila/cytology , Larva/cytology , Larva/physiology , Nerve Tissue Proteins/genetics , Proteoglycans/metabolism , Receptors, Immunologic/genetics , cdc42 GTP-Binding Protein/metabolism , Roundabout Proteins
8.
PLoS One ; 11(2): e0148978, 2016.
Article in English | MEDLINE | ID: mdl-26866694

ABSTRACT

Blood cell production in the Drosophila hematopoietic organ, the lymph gland, is controlled by intrinsic factors and extrinsic signals. Initial analysis of Collier/Early B Cell Factor function in the lymph gland revealed the role of the Posterior Signaling Center (PSC) in mounting a dedicated cellular immune response to wasp parasitism. Further, premature blood cell differentiation when PSC specification or signaling was impaired, led to assigning the PSC a role equivalent to the vertebrate hematopoietic niche. We report here that Collier is expressed in a core population of lymph gland progenitors and cell autonomously maintains this population. The PSC contributes to lymph gland homeostasis by regulating blood cell differentiation, rather than by maintaining core progenitors. In addition to PSC signaling, switching off Collier expression in progenitors is required for efficient immune response to parasitism. Our data show that two independent sites of Collier/Early B Cell Factor expression, hematopoietic progenitors and the PSC, achieve control of hematopoiesis.


Subject(s)
Drosophila Proteins/metabolism , Drosophila melanogaster/physiology , Hemocytes/cytology , Lymph/physiology , Transcription Factors/metabolism , Animals , Cell Differentiation , Gene Expression Regulation, Developmental , Green Fluorescent Proteins/metabolism , Hematopoiesis , Homeostasis , Host-Parasite Interactions , Immune System , In Situ Hybridization , Mitosis , RNA Interference , Signal Transduction , Stem Cell Niche , Stem Cells , Wasps
9.
Med Sci (Paris) ; 30(1): 76-81, 2014 Jan.
Article in French | MEDLINE | ID: mdl-24472463

ABSTRACT

Stem cells are required for both tissue renewal and repair in response to injury. The maintenance and function of stem cells is controlled by their specific cellular microenvironment called "niche". Hematopoietic stem cells (HSC) that give rise to all blood cell types have been extensively studied in mammals. Genetic and molecular analyses performed in mice identified several signaling pathways involved in the cellular communications between HSC and their niche. However, hematopoietic niche plasticity remains poorly understood. The discovery of a Drosophila hematopoietic niche, called PSC, established a new model to decipher the niche function in vivo. Size control of the PSC is essential to maintain hematopoietic tissue homeostasis and a molecular cascade controlling the PSC cell number has been characterized. Novel parallels between Drosophila and mammalian hematopoietic niches open new perspectives for studies of HSC biology in human.


Subject(s)
Drosophila , Hematopoietic Stem Cells/cytology , Hematopoietic Stem Cells/physiology , Stem Cell Niche/physiology , Animals , Drosophila/cytology , Drosophila/physiology , Hematopoiesis/physiology , Humans , Mammals , Mice , Models, Biological
10.
Mol Biol Cell ; 22(6): 726-35, 2011 Mar 15.
Article in English | MEDLINE | ID: mdl-21233286

ABSTRACT

In mammalian cells, nontranslating messenger RNAs (mRNAs) are concentrated in different cytoplasmic foci, such as processing bodies (PBs) and stress granules (SGs), where they are either degraded or stored. In the present study, we have thoroughly characterized cytoplasmic foci, hereafter called AGs for ALK granules that form in transformed cells expressing the constitutively active anaplastic lymphoma kinase (ALK). AGs contain polyadenylated mRNAs and a unique combination of several RNA binding proteins that so far has not been described in mammalian foci, including AUF1, HuR, and the poly (A(+)) binding protein PABP. AGs shelter neither components of the mRNA degradation machinery present in PBs nor known markers of SGs, such as translation initiation factors or TIA/TIAR, showing that they are distinct from PBs or SGs. AGs and PBs, however, both move on microtubules with similar dynamics and frequently establish close contacts. In addition, in conditions in which mRNA metabolism is perturbed, AGs concentrate PB components with the noticeable exception of the 5' to 3' exonuclease XRN1. Altogether, we show that AGs constitute novel mRNA-containing cytoplasmic foci and we propose that they could protect translatable mRNAs from degradation, contributing thus to ALK-mediated oncogenicity.


Subject(s)
Cell Transformation, Neoplastic , Cytoplasmic Granules/genetics , Cytoplasmic Granules/metabolism , RNA, Messenger/metabolism , Receptor Protein-Tyrosine Kinases/metabolism , Anaplastic Lymphoma Kinase , Animals , Cycloheximide/pharmacology , Cytoplasmic Granules/chemistry , Humans , Mice , NIH 3T3 Cells/drug effects , Protein Synthesis Inhibitors/pharmacology , RNA, Messenger/genetics , Receptor Protein-Tyrosine Kinases/genetics , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism
11.
J Bioinform Comput Biol ; 8(1): 1-17, 2010 Feb.
Article in English | MEDLINE | ID: mdl-20183871

ABSTRACT

The structures attained by RNA molecules depend not only on their sequence but also on environmental parameters such as their temperature. So far, this effect has been largely neglected in bioinformatics studies. Here, we show that structural comparisons can be facilitated and more coherent structural models can be obtained when differences in environmental parameters are taken into account. We re-evaluate the secondary structures of the spliced leader (SL) RNAs from the seven eukaryotic phyla in which SL RNA trans-splicing has been described. Adjusting structure prediction to the natural growth temperatures and considering energetically similar secondary structures, we observe striking similarities among Euglenida, Kinetoplastida, Dinophyceae, Cnidaria, Rotifera, Nematoda, Platyhelminthes, and Tunicata that cannot be explained easily by the independent innovation of SL RNAs in each of these phyla. Supplementary Table is available at http://www.worldscinet.com/jbcb/.


Subject(s)
RNA, Spliced Leader/chemistry , RNA, Spliced Leader/genetics , Algorithms , Animals , Base Sequence , Computational Biology , Eukaryota , Evolution, Molecular , Humans , Models, Biological , Nucleic Acid Conformation , Phylogeny , RNA Splicing , Sequence Homology, Nucleic Acid , Temperature , Thermodynamics
12.
PLoS One ; 4(3): e4900, 2009.
Article in English | MEDLINE | ID: mdl-19333380

ABSTRACT

BACKGROUND: In mammals, a temporal disconnection between mRNA transcription and protein synthesis occurs during late steps of germ cell differentiation, in contrast to most somatic tissues where transcription and translation are closely linked. Indeed, during late stages of spermatogenesis, protein synthesis relies on the appropriate storage of translationally inactive mRNAs in transcriptionally silent spermatids. The factors and cellular compartments regulating mRNA storage and the timing of their translation are still poorly understood. The chromatoid body (CB), that shares components with the P. bodies found in somatic cells, has recently been proposed to be a site of mRNA processing. Here, we describe a new component of the CB, the RNA binding protein HuR, known in somatic cells to control the stability/translation of AU-rich containing mRNAs (ARE-mRNAs). METHODOLOGY/PRINCIPAL FINDINGS: Using a combination of cell imagery and sucrose gradient fractionation, we show that HuR localization is highly dynamic during spermatid differentiation. First, in early round spermatids, HuR colocalizes with the Mouse Vasa Homolog, MVH, a marker of the CB. As spermatids differentiate, HuR exits the CB and concomitantly associates with polysomes. Using computational analyses, we identified two testis ARE-containing mRNAs, Brd2 and GCNF that are bound by HuR and MVH. We show that these target ARE-mRNAs follow HuR trafficking, accumulating successively in the CB, where they are translationally silent, and in polysomes during spermatid differentiation. CONCLUSIONS/SIGNIFICANCE: Our results reveal a temporal regulation of HuR trafficking together with its target mRNAs from the CB to polysomes as spermatids differentiate. They strongly suggest that through the transport of ARE-mRNAs from the CB to polysomes, HuR controls the appropriate timing of ARE-mRNA translation. HuR might represent a major post-transcriptional regulator, by promoting mRNA storage and then translation, during male germ cell differentiation.


Subject(s)
Antigens, Surface/metabolism , Polyribosomes/metabolism , RNA, Messenger/metabolism , RNA-Binding Proteins/metabolism , Spermatogenesis , Animals , Antigens, Surface/genetics , Antigens, Surface/physiology , Cell Differentiation , ELAV Proteins , ELAV-Like Protein 1 , Male , Mice , Protein Transport , RNA Stability , RNA-Binding Proteins/genetics , RNA-Binding Proteins/physiology , Spermatids/cytology , Testis , Time Factors
13.
Mol Cell Biol ; 29(10): 2636-43, 2009 May.
Article in English | MEDLINE | ID: mdl-19273595

ABSTRACT

In mammals, AU-rich elements (AREs) are critical regulators of mRNA turnover. They recruit ARE-binding proteins that inhibit or stimulate rapid mRNA degradation in response to stress or developmental cues. Using a bioinformatics approach, we have identified AREs in Drosophila melanogaster 3' untranslated regions and validated their cross-species conservation in distant Drosophila genomes. We have generated a Drosophila ARE database (D-ARED) and established that about 16% of D. melanogaster genes contain the mammalian ARE signature, an AUUUA pentamer in an A/U-rich context. Using candidate ARE genes, we show that Drosophila AREs stimulate reporter mRNA decay in cultured cells and in the physiological context of the immune response in D. melanogaster. In addition, we found that the conserved ARE-binding protein Tis11 regulates temporal gene expression through ARE-mediated decay (AMD) in D. melanogaster. Our work reveals that AREs are conserved and functional cis regulators of mRNA decay in Drosophila and highlights this organism as a novel model system to unravel in vivo the contribution of AMD to various processes.


Subject(s)
Base Sequence , Drosophila/genetics , Gene Expression Regulation , Gene Expression , RNA, Messenger/metabolism , Sequence Analysis, DNA , Animals , Antimicrobial Cationic Peptides/genetics , Antimicrobial Cationic Peptides/metabolism , Databases, Genetic , Drosophila/metabolism , Genes, Reporter , Molecular Sequence Data , RNA Stability , RNA, Messenger/genetics , Sequence Alignment , Tristetraprolin/genetics , Tristetraprolin/metabolism
14.
Dev Cell ; 12(4): 543-55, 2007 Apr.
Article in English | MEDLINE | ID: mdl-17419993

ABSTRACT

In Drosophila, localized activity of oskar at the posterior pole of the oocyte induces germline and abdomen formation in the embryo. Oskar has two isoforms, a short isoform encoding the patterning determinant and a long isoform of unknown function. Here, we show by immuno-electron microscopy that the two Oskar isoforms have different subcellular localizations in the oocyte: Short Oskar mainly localizes to polar granules, and Long Oskar is specifically associated with endocytic membranes along the posterior cortex. Our cell biological and genetic analyses reveal that Oskar stimulates endocytosis, and that its two isoforms are required to regulate this process. Furthermore, we describe long F-actin projections at the oocyte posterior pole that are induced by and intermingled with Oskar protein. We propose that Oskar maintains its localization at the posterior pole through dual functions in regulating endocytosis and F-actin dynamics.


Subject(s)
Actins/metabolism , Cell Polarity , Drosophila Proteins/metabolism , Drosophila melanogaster/metabolism , Endocytosis , Oocytes/metabolism , Animals , Animals, Genetically Modified , Cell Membrane/metabolism , Clathrin/metabolism , Clathrin/physiology , Drosophila Proteins/genetics , Drosophila melanogaster/physiology , Female , In Vitro Techniques , Microscopy, Immunoelectron , Models, Biological , Oocytes/physiology , Oocytes/ultrastructure , Protein Isoforms , Up-Regulation
15.
J Mol Biol ; 367(1): 113-32, 2007 Mar 16.
Article in English | MEDLINE | ID: mdl-17234211

ABSTRACT

The Escherichia coli protein RhlB is an ATP-dependent motor that unfolds structured RNA for destruction by partner ribonucleases. In E. coli, and probably many other related gamma-proteobacteria, RhlB associates with the essential endoribonuclease RNase E as part of the multi-enzyme RNA degradosome assembly. The interaction with RNase E boosts RhlB's ATPase activity by an order of magnitude. Here, we examine the origins and implications of this effect. The location of the interaction sites on both RNase E and RhlB are refined and analysed using limited protease digestion, domain cross-linking and homology modelling. These data indicate that RhlB's carboxy-terminal RecA-like domain engages a segment of RNase E that is no greater than 64 residues. The interaction between RhlB and RNase E has two important consequences: first, the interaction itself stimulates the unwinding and ATPase activities of RhlB; second, RhlB gains proximity to two RNA-binding sites on RNase E, with which it cooperates to unwind RNA. Our homology model identifies a pattern of residues in RhlB that may be key for recognition of RNase E and which may communicate the activating effects. Our data also suggest that the association with RNase E may partially repress the RNA-binding activity of RhlB. This repression may in fact permit the interplay of the helicase and adjacent RNA binding segments as part of a process that steers substrates to either processing or destruction, depending on context, within the RNA degradosome assembly.


Subject(s)
Adenosine Triphosphate/metabolism , DEAD-box RNA Helicases/metabolism , Endoribonucleases/metabolism , Escherichia coli Proteins/metabolism , Escherichia coli/enzymology , Adenosine Triphosphatases/metabolism , Escherichia coli/metabolism , Multienzyme Complexes/metabolism , Nucleic Acid Denaturation , Polyribonucleotide Nucleotidyltransferase/metabolism , RNA/metabolism , RNA Helicases/metabolism
16.
Mol Microbiol ; 54(5): 1422-30, 2004 Dec.
Article in English | MEDLINE | ID: mdl-15554979

ABSTRACT

The non-catalytic region of Escherichia coli RNase E contains a protein scaffold that binds to the other components of the RNA degradosome. Alanine scanning yielded a mutation, R730A, that disrupts the interaction between RNase E and the DEAD-box RNA helicase, RhlB. We show that three other DEAD-box helicases, SrmB, RhlE and CsdA also bind to RNase E in vitro. Their binding differs from that of RhlB because it is not affected by the R730A mutation. Furthermore, the deletion of residues 791-843, which does not affect RhlB binding, disrupts the binding of SrmB, RhlE and CsdA. Therefore, RNase E has at least two RNA helicase binding sites. Reconstitution of a complex containing the protein scaffold of RNase E, PNPase and RhlE shows that RhlE can furnish an ATP-dependent activity that facilitates the degradation of structured RNA by PNPase. Thus, RhlE can replace the function of RhlB in vitro. The results in the accompanying article show that CsdA can also replace RhlB in vitro. Thus, RhlB, RhlE and CsdA are interchangeable in in vitro RNA degradation assays.


Subject(s)
Endoribonucleases/genetics , Endoribonucleases/metabolism , Escherichia coli/enzymology , RNA Helicases/metabolism , Adenosine Triphosphatases/metabolism , Amino Acid Substitution , Binding Sites , Escherichia coli Proteins/genetics , Escherichia coli Proteins/metabolism , Genes, Bacterial , Multienzyme Complexes/genetics , Multienzyme Complexes/metabolism , Mutation , Polyribonucleotide Nucleotidyltransferase/genetics , Polyribonucleotide Nucleotidyltransferase/metabolism , Protein Binding , RNA Helicases/genetics , Sequence Deletion
17.
Mech Dev ; 120(9): 1071-81, 2003 Sep.
Article in English | MEDLINE | ID: mdl-14550535

ABSTRACT

Many cells store neutral lipids, as triacylglycerol and sterol esters, in droplets. PAT-domain proteins form a conserved family of proteins that are localized at the surface of neutral lipid droplets. Two mammalian members of this family, Perilipin and adipose differentiation-related protein, are involved in lipid storage and regulate lipolysis. Here, we describe the Drosophila PAT-family member Lsd2. We showed that Lsd2 is predominantly expressed in tissues engaged in high levels of lipid metabolism, the fat body and the germ line of females. Ultrastructural analysis in the germ line showed that Lsd2 localizes to the surface of lipid droplets. We have generated an Lsd2 mutant and described its phenotype. Mutant adults have a reduced level of neutral lipid content compared to wild type, showing that Lsd2 is required for normal lipid storage. In addition, ovaries from Lsd2 mutant females exhibit an abnormal pattern of accumulation of neutral lipids from mid-oogenesis, which results in reduced deposition of lipids in the egg. Consistent with its expression in the female germ line, we showed that Lsd2 is a maternal effect gene that is required for normal embryogenesis. This work demonstrates that Lsd2 has an evolutionarily conserved function in lipid metabolism and establishes Drosophila melanogaster as a new in vivo model for studies on the PAT-family of proteins.


Subject(s)
Drosophila Proteins/metabolism , Lipid Metabolism , Membrane Proteins/metabolism , Phosphoproteins/metabolism , Animals , Animals, Genetically Modified , Carrier Proteins , Drosophila Proteins/genetics , Drosophila melanogaster/genetics , Drosophila melanogaster/growth & development , Drosophila melanogaster/metabolism , Evolution, Molecular , Fat Body/embryology , Fat Body/growth & development , Fat Body/metabolism , Female , Gene Expression Regulation, Developmental , Genes, Insect , Male , Membrane Proteins/genetics , Mutation , Oogenesis , Perilipin-1 , Phosphoproteins/genetics
18.
Mol Microbiol ; 45(5): 1231-43, 2002 Sep.
Article in English | MEDLINE | ID: mdl-12207692

ABSTRACT

RNase E contains a large non-catalytic region that binds RNA and the protein components of the Escherichia coli RNA degradosome. The rne gene was replaced with alleles encoding deletions in the non-catalytic part of RNase E. All the proteins are stable in vivo. RNase E activity was tested using a P(T7)-lacZ reporter gene, the message of which is particularly sensitive to degradation because translation is uncoupled from transcription. The non-catalytic region has positive and negative effectors of mRNA degradation. Disrupting RhlB and enolase binding resulted in hypoactivity, whereas disrupting PNPase binding resulted in hyperactivity. Expression of the mutant proteins in vivo anticorrelates with activity showing that autoregulation compensates for defective function. There is no simple correlation between RNA binding and activity in vivo. An allele (rne131), expressing the catalytic domain alone, was put under P(lac) control. In contrast to rne+,low expression of rne131 severely affects growth. Even with autoregulation, all the mutants are less fit when grown in competition with wild type. Although the catalytic domain of RNase E is sufficient for viability, our work demonstrates that elements in the non-catalytic part are necessary for normal activity in vivo.


Subject(s)
Endoribonucleases/chemistry , Endoribonucleases/metabolism , Escherichia coli/metabolism , RNA, Bacterial/metabolism , RNA, Messenger/metabolism , Endoribonucleases/genetics , Escherichia coli/enzymology , Escherichia coli/genetics , Escherichia coli/growth & development , Gene Expression Regulation, Bacterial , Gene Expression Regulation, Enzymologic , Genes, Bacterial , Genes, Reporter , Lac Operon , RNA Stability , Sequence Deletion
19.
Development ; 129(15): 3705-14, 2002 Aug.
Article in English | MEDLINE | ID: mdl-12117819

ABSTRACT

Localization of the maternal determinant Oskar at the posterior pole of Drosophila melanogaster oocyte provides the positional information for pole plasm formation. Spatial control of Oskar expression is achieved through the tight coupling of mRNA localization to translational control, such that only posterior-localized oskar mRNA is translated, producing the two Oskar isoforms Long Osk and Short Osk. We present evidence that this coupling is not sufficient to restrict Oskar to the posterior pole of the oocyte. We show that Long Osk anchors both oskar mRNA and Short Osk, the isoform active in pole plasm assembly, at the posterior pole. In the absence of anchoring by Long Osk, Short Osk disperses into the bulk cytoplasm during late oogenesis, impairing pole cell formation in the embryo. In addition, the pool of untethered Short Osk causes anteroposterior patterning defects, owing to the dispersion of pole plasm and its abdomen-inducing activity throughout the oocyte. We show that the N-terminal extension of Long Osk is necessary but not sufficient for posterior anchoring, arguing for multiple docking elements in Oskar. This study reveals cortical anchoring of the posterior determinant Oskar as a crucial step in pole plasm assembly and restriction, required for proper development of Drosophila melanogaster.


Subject(s)
Cell Polarity/physiology , Cytoplasm/metabolism , Drosophila Proteins/metabolism , Drosophila melanogaster/embryology , Oocytes/physiology , Animals , Body Patterning/physiology , Drosophila Proteins/genetics , Drosophila melanogaster/genetics , Female , In Situ Hybridization , Male , Oocytes/cytology , Oogenesis/physiology , Protein Isoforms , Protein Structure, Tertiary , RNA, Messenger/metabolism , Recombinant Fusion Proteins , Transgenes
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