1
|
Chekulaeva M. Mechanistic insights into the basis of widespread RNA localization. Nat Cell Biol 2024; 26:1037-1046. [PMID: 38956277 DOI: 10.1038/s41556-024-01444-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Accepted: 05/20/2024] [Indexed: 07/04/2024]
Abstract
The importance of subcellular mRNA localization is well established, but the underlying mechanisms mostly remain an enigma. Early studies suggested that specific mRNA sequences recruit RNA-binding proteins (RBPs) to regulate mRNA localization. However, despite the observation of thousands of localized mRNAs, only a handful of these sequences and RBPs have been identified. This suggests the existence of alternative, and possibly predominant, mechanisms for mRNA localization. Here I re-examine currently described mRNA localization mechanisms and explore alternative models that could account for its widespread occurrence.
Collapse
Affiliation(s)
- Marina Chekulaeva
- Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany.
| |
Collapse
|
2
|
Zhao H, Shi L, Li Z, Kong R, Jia L, Lu S, Wang JH, Dong MQ, Guo X, Li Z. Diamond controls epithelial polarity through the dynactin-dynein complex. Traffic 2023; 24:552-563. [PMID: 37642208 DOI: 10.1111/tra.12917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 07/10/2023] [Accepted: 08/21/2023] [Indexed: 08/31/2023]
Abstract
Epithelial polarity is critical for proper functions of epithelial tissues, tumorigenesis, and metastasis. The evolutionarily conserved transmembrane protein Crumbs (Crb) is a key regulator of epithelial polarity. Both Crb protein and its transcripts are apically localized in epithelial cells. However, it remains not fully understood how they are targeted to the apical domain. Here, using Drosophila ovarian follicular epithelia as a model, we show that epithelial polarity is lost and Crb protein is absent in the apical domain in follicular cells (FCs) in the absence of Diamond (Dind). Interestingly, Dind is found to associate with different components of the dynactin-dynein complex through co-IP-MS analysis. Dind stabilizes dynactin and depletion of dynactin results in almost identical defects as those observed in dind-defective FCs. Finally, both Dind and dynactin are also required for the apical localization of crb transcripts in FCs. Thus our data illustrate that Dind functions through dynactin/dynein-mediated transport of both Crb protein and its transcripts to the apical domain to control epithelial apico-basal (A/B) polarity.
Collapse
Affiliation(s)
- Hang Zhao
- College of Life Sciences, Capital Normal University, Beijing, China
| | - Lin Shi
- College of Life Sciences, Capital Normal University, Beijing, China
| | - Zhengran Li
- College of Life Sciences, Capital Normal University, Beijing, China
| | - Ruiyan Kong
- College of Life Sciences, Capital Normal University, Beijing, China
| | - Lemei Jia
- National Institute of Biological Sciences (NIBS), Beijing, China
| | - Shan Lu
- National Institute of Biological Sciences (NIBS), Beijing, China
| | - Jian-Hua Wang
- National Institute of Biological Sciences (NIBS), Beijing, China
| | - Meng-Qiu Dong
- National Institute of Biological Sciences (NIBS), Beijing, China
| | - Xuan Guo
- Life Science Institute, Jinzhou Medical University, Jinzhou, Liaoning, China
| | - Zhouhua Li
- College of Life Sciences, Capital Normal University, Beijing, China
| |
Collapse
|
3
|
Curnutte HA, Lan X, Sargen M, Ao Ieong SM, Campbell D, Kim H, Liao Y, Lazar SB, Trcek T. Proteins rather than mRNAs regulate nucleation and persistence of Oskar germ granules in Drosophila. Cell Rep 2023; 42:112723. [PMID: 37384531 PMCID: PMC10439980 DOI: 10.1016/j.celrep.2023.112723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 04/24/2023] [Accepted: 06/13/2023] [Indexed: 07/01/2023] Open
Abstract
RNA granules are membraneless condensates that provide functional compartmentalization within cells. The mechanisms by which RNA granules form are under intense investigation. Here, we characterize the role of mRNAs and proteins in the formation of germ granules in Drosophila. Super-resolution microscopy reveals that the number, size, and distribution of germ granules is precisely controlled. Surprisingly, germ granule mRNAs are not required for the nucleation or the persistence of germ granules but instead control their size and composition. Using an RNAi screen, we determine that RNA regulators, helicases, and mitochondrial proteins regulate germ granule number and size, while the proteins of the endoplasmic reticulum, nuclear pore complex, and cytoskeleton control their distribution. Therefore, the protein-driven formation of Drosophila germ granules is mechanistically distinct from the RNA-dependent condensation observed for other RNA granules such as stress granules and P-bodies.
Collapse
Affiliation(s)
- Harrison A Curnutte
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Xinyue Lan
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Manuel Sargen
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Si Man Ao Ieong
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Dylan Campbell
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Hyosik Kim
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Yijun Liao
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Sarah Bailah Lazar
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Tatjana Trcek
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA.
| |
Collapse
|
4
|
Chiappetta A, Liao J, Tian S, Trcek T. Structural and functional organization of germ plasm condensates. Biochem J 2022; 479:2477-2495. [PMID: 36534469 PMCID: PMC10722471 DOI: 10.1042/bcj20210815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 11/08/2022] [Accepted: 11/11/2022] [Indexed: 12/23/2022]
Abstract
Reproductive success of metazoans relies on germ cells. These cells develop early during embryogenesis, divide and undergo meiosis in the adult to make sperm and oocytes. Unlike somatic cells, germ cells are immortal and transfer their genetic material to new generations. They are also totipotent, as they differentiate into different somatic cell types. The maintenance of immortality and totipotency of germ cells depends on extensive post-transcriptional and post-translational regulation coupled with epigenetic remodeling, processes that begin with the onset of embryogenesis [1, 2]. At the heart of this regulation lie germ granules, membraneless ribonucleoprotein condensates that are specific to the germline cytoplasm called the germ plasm. They are a hallmark of all germ cells and contain several proteins and RNAs that are conserved across species. Interestingly, germ granules are often structured and tend to change through development. In this review, we describe how the structure of germ granules becomes established and discuss possible functional outcomes these structures have during development.
Collapse
|
5
|
Bose M, Lampe M, Mahamid J, Ephrussi A. Liquid-to-solid phase transition of oskar ribonucleoprotein granules is essential for their function in Drosophila embryonic development. Cell 2022; 185:1308-1324.e23. [PMID: 35325593 PMCID: PMC9042795 DOI: 10.1016/j.cell.2022.02.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 11/24/2021] [Accepted: 02/18/2022] [Indexed: 01/05/2023]
Abstract
Asymmetric localization of oskar ribonucleoprotein (RNP) granules to the oocyte posterior is crucial for abdominal patterning and germline formation in the Drosophila embryo. We show that oskar RNP granules in the oocyte are condensates with solid-like physical properties. Using purified oskar RNA and scaffold proteins Bruno and Hrp48, we confirm in vitro that oskar granules undergo a liquid-to-solid phase transition. Whereas the liquid phase allows RNA incorporation, the solid phase precludes incorporation of additional RNA while allowing RNA-dependent partitioning of client proteins. Genetic modification of scaffold granule proteins or tethering the intrinsically disordered region of human fused in sarcoma (FUS) to oskar mRNA allowed modulation of granule material properties in vivo. The resulting liquid-like properties impaired oskar localization and translation with severe consequences on embryonic development. Our study reflects how physiological phase transitions shape RNA-protein condensates to regulate the localization and expression of a maternal RNA that instructs germline formation.
Collapse
Affiliation(s)
- Mainak Bose
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany
| | - Marko Lampe
- Advanced Light Microscopy Facility, European Molecular Biology Laboratory, Heidelberg 69117, Germany
| | - Julia Mahamid
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany.
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany.
| |
Collapse
|
6
|
Blondel L, Besse S, Rivard EL, Ylla G, Extavour CG. Evolution of a cytoplasmic determinant: evidence for the biochemical basis of functional evolution of the novel germ line regulator oskar. Mol Biol Evol 2021; 38:5491-5513. [PMID: 34550378 PMCID: PMC8662646 DOI: 10.1093/molbev/msab284] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Germ line specification is essential in sexually reproducing organisms. Despite their critical role, the evolutionary history of the genes that specify animal germ cells is heterogeneous and dynamic. In many insects, the gene oskar is required for the specification of the germ line. However, the germ line role of oskar is thought to be a derived role resulting from co-option from an ancestral somatic role. To address how evolutionary changes in protein sequence could have led to changes in the function of Oskar protein that enabled it to regulate germ line specification, we searched for oskar orthologs in 1,565 publicly available insect genomic and transcriptomic data sets. The earliest-diverging lineage in which we identified an oskar ortholog was the order Zygentoma (silverfish and firebrats), suggesting that oskar originated before the origin of winged insects. We noted some order-specific trends in oskar sequence evolution, including whole gene duplications, clade-specific losses, and rapid divergence. An alignment of all known 379 Oskar sequences revealed new highly conserved residues as candidates that promote dimerization of the LOTUS domain. Moreover, we identified regions of the OSK domain with conserved predicted RNA binding potential. Furthermore, we show that despite a low overall amino acid conservation, the LOTUS domain shows higher conservation of predicted secondary structure than the OSK domain. Finally, we suggest new key amino acids in the LOTUS domain that may be involved in the previously reported Oskar−Vasa physical interaction that is required for its germ line role.
Collapse
Affiliation(s)
- Leo Blondel
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
| | - Savandara Besse
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
| | - Emily L Rivard
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
| | - Guillem Ylla
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Cassandra G Extavour
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA.,Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
| |
Collapse
|
7
|
Receptor-mediated yolk uptake is required for oskar mRNA localization and cortical anchorage of germ plasm components in the Drosophila oocyte. PLoS Biol 2021; 19:e3001183. [PMID: 33891588 PMCID: PMC8064586 DOI: 10.1371/journal.pbio.3001183] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 03/11/2021] [Indexed: 11/22/2022] Open
Abstract
The Drosophila germ plasm is responsible for germ cell formation. Its assembly begins with localization of oskar mRNA to the posterior pole of the oocyte. The oskar translation produces 2 isoforms with distinct functions: short Oskar recruits germ plasm components, whereas long Oskar remodels actin to anchor the components to the cortex. The mechanism by which long Oskar anchors them remains elusive. Here, we report that Yolkless, which facilitates uptake of nutrient yolk proteins into the oocyte, is a key cofactor for long Oskar. Loss of Yolkless or depletion of yolk proteins disrupts the microtubule alignment and oskar mRNA localization at the posterior pole of the oocyte, whereas microtubule-dependent localization of bicoid mRNA to the anterior and gurken mRNA to the anterior-dorsal corner remains intact. Furthermore, these mutant oocytes do not properly respond to long Oskar, causing defects in the actin remodeling and germ plasm anchoring. Thus, the yolk uptake is not merely the process for nutrient incorporation, but also crucial for oskar mRNA localization and cortical anchorage of germ plasm components in the oocyte. A study of the fruit fly Drosophila reveals that receptor-mediated yolk uptake is not merely a nutrient storage process for future embryogenesis, but is also required for localization of Oskar mRNA and cortical anchorage of germ plasm components in the oocyte during oogenesis.
Collapse
|
8
|
Kenny A, Morgan MB, Macdonald PM. Different roles for the adjoining and structurally similar A-rich and poly(A) domains of oskar mRNA: Only the A-rich domain is required for oskar noncoding RNA function, which includes MTOC positioning. Dev Biol 2021; 476:117-127. [PMID: 33798537 DOI: 10.1016/j.ydbio.2021.03.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Revised: 03/23/2021] [Accepted: 03/24/2021] [Indexed: 11/17/2022]
Abstract
Drosophila oskar (osk) mRNA has both coding and noncoding functions, with the latter required for progression through oogenesis. Noncoding activity is mediated by the osk 3' UTR. Three types of cis elements act most directly and are clustered within the final ~120 nucleotides of the 3' UTR: multiple binding sites for the Bru1 protein, a short highly conserved region, and A-rich sequences abutting the poly(A) tail. Here we extend the characterization of these elements and their functions, providing new insights into osk noncoding RNA function and the makeup of the cis elements. We show that all three elements are required for correct positioning of the microtubule organizing center (MTOC), a defect not previously reported for any osk mutant. Normally, the MTOC is located at the posterior of the oocyte during previtellogenic stages of oogenesis, and this distribution underlies the strong posterior enrichment of many mRNAs transported into the oocyte from the nurse cells. When osk noncoding function was disrupted the MTOC was dispersed in the oocyte and osk mRNA failed to be enriched at the posterior, although transport to the oocyte was not affected. A previous study did not detect loss of posterior enrichment for certain osk mutants lacking noncoding activity (Kanke et al., 2015). This discrepancy may be due to use of imaging aimed at monitoring transport to the oocyte rather than posterior enrichment. Involvement in MTOC positioning suggests that the osk noncoding function may act in conjunction with genes whose loss has similar effects, and that osk function may extend to other processes requiring those genes. Further characterization of the cis elements required for osk noncoding function included completion of saturation mutagenesis of the most highly conserved region, providing critical information for evaluating the possible contribution of candidate binding factors. The 3'-most cis element is a cluster of A-rich sequences, the ARS. The close juxtaposition and structural similarity of the ARS and poly(A) tail raised the possibility that they comprise an extended A-rich element required for osk noncoding function. We found that absence of the poly(A) tail did not mimic the effects of mutation of the ARS, causing neither arrest of oogenesis nor mispositioning of osk mRNA in previtellogenic stage oocytes. Thus, the ARS and the poly(A) tail are not interchangeable for osk noncoding RNA function, suggesting that the role of the ARS is not in recruitment of Poly(A) binding protein (PABP), the protein that binds the poly(A) tail. Furthermore, although PABP has been implicated in transport of osk mRNA from the nurse cells to the oocyte, mutation of the ARS in combination with loss of the poly(A) tail did not disrupt transport of osk mRNA into the oocyte. We conclude that PABP acts indirectly in osk mRNA transport, or is associated with osk mRNA independent of an A-rich binding site. Although the poly(A) tail was not required for osk mRNA transport into the oocyte, its absence was associated with a novel osk mRNA localization defect later in oogenesis, potentially revealing a previously unrecognized step in the localization process.
Collapse
Affiliation(s)
- Andrew Kenny
- Department of Molecular Biosciences, The University of Texas at Austin, United States
| | - Miles B Morgan
- Department of Molecular Biosciences, The University of Texas at Austin, United States
| | - Paul M Macdonald
- Department of Molecular Biosciences, The University of Texas at Austin, United States.
| |
Collapse
|
9
|
Aoki ST, Lynch TR, Crittenden SL, Bingman CA, Wickens M, Kimble J. C. elegans germ granules require both assembly and localized regulators for mRNA repression. Nat Commun 2021; 12:996. [PMID: 33579952 PMCID: PMC7881195 DOI: 10.1038/s41467-021-21278-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 01/14/2021] [Indexed: 02/07/2023] Open
Abstract
Cytoplasmic RNA-protein (RNP) granules have diverse biophysical properties, from liquid to solid, and play enigmatic roles in RNA metabolism. Nematode P granules are paradigmatic liquid droplet granules and central to germ cell development. Here we analyze a key P granule scaffolding protein, PGL-1, to investigate the functional relationship between P granule assembly and function. Using a protein-RNA tethering assay, we find that reporter mRNA expression is repressed when recruited to PGL-1. We determine the crystal structure of the PGL-1 N-terminal region to 1.5 Å, discover its dimerization, and identify key residues at the dimer interface. Mutations of those interface residues prevent P granule assembly in vivo, de-repress PGL-1 tethered mRNA, and reduce fertility. Therefore, PGL-1 dimerization lies at the heart of both P granule assembly and function. Finally, we identify the P granule-associated Argonaute WAGO-1 as crucial for repression of PGL-1 tethered mRNA. We conclude that P granule function requires both assembly and localized regulators.
Collapse
Affiliation(s)
- Scott Takeo Aoki
- grid.257413.60000 0001 2287 3919Department of Biochemistry and Molecular Biology, School of Medicine, Indiana University, Indianapolis, IN USA ,grid.14003.360000 0001 2167 3675Department of Biochemistry, University of Wisconsin-Madison, Madison, WI USA
| | - Tina R. Lynch
- grid.14003.360000 0001 2167 3675Department of Biochemistry, University of Wisconsin-Madison, Madison, WI USA
| | - Sarah L. Crittenden
- grid.14003.360000 0001 2167 3675Department of Biochemistry, University of Wisconsin-Madison, Madison, WI USA ,grid.14003.360000 0001 2167 3675Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, WI USA
| | - Craig A. Bingman
- grid.14003.360000 0001 2167 3675Department of Biochemistry, University of Wisconsin-Madison, Madison, WI USA
| | - Marvin Wickens
- grid.14003.360000 0001 2167 3675Department of Biochemistry, University of Wisconsin-Madison, Madison, WI USA
| | - Judith Kimble
- grid.14003.360000 0001 2167 3675Department of Biochemistry, University of Wisconsin-Madison, Madison, WI USA ,grid.14003.360000 0001 2167 3675Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, WI USA
| |
Collapse
|
10
|
Mukherjee N, Mukherjee C. Germ cell ribonucleoprotein granules in different clades of life: From insects to mammals. WILEY INTERDISCIPLINARY REVIEWS-RNA 2021; 12:e1642. [PMID: 33555143 DOI: 10.1002/wrna.1642] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 01/04/2021] [Accepted: 01/05/2021] [Indexed: 12/12/2022]
Abstract
Ribonucleoprotein (RNP) granules are no newcomers in biology. Found in all life forms, ranging across taxa, these membrane-less "organelles" have been classified into different categories based on their composition, structure, behavior, function, and localization. Broadly, they can be listed as stress granules (SGs), processing bodies (PBs), neuronal granules (NGs), and germ cell granules (GCGs). Keeping in line with the topic of this review, RNP granules present in the germ cells have been implicated in a wide range of cellular functions including cellular specification, differentiation, proliferation, and so forth. The mechanisms used by them can be diverse and many of them remain partly obscure and active areas of research. GCGs can be of different types in different organisms and at different stages of development, with multiple types coexisting in the same cell. In this review, the different known subcategories of GCGs have been studied with respect to five distinct model organisms, namely, Drosophila, Caenorhabditis elegans, Xenopus, Zebrafish, and mammals. Of them, the cytoplasmic polar granules in Drosophila, P granules in C. elegans, balbiani body in Xenopus and Zebrafish, and chromatoid bodies in mammals have been specifically emphasized upon. A descriptive account of the same has been provided along with insights into our current understanding of their functional significance with respect to cellular events relating to different developmental and reproductive processes. This article is categorized under: RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes RNA Export and Localization > RNA Localization RNA in Disease and Development > RNA in Disease.
Collapse
|
11
|
Lasko P. Patterning the Drosophila embryo: A paradigm for RNA-based developmental genetic regulation. WILEY INTERDISCIPLINARY REVIEWS-RNA 2020; 11:e1610. [PMID: 32543002 PMCID: PMC7583483 DOI: 10.1002/wrna.1610] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 05/13/2020] [Accepted: 05/17/2020] [Indexed: 12/16/2022]
Abstract
Embryonic anterior–posterior patterning is established in Drosophila melanogaster by maternally expressed genes. The mRNAs of several of these genes accumulate at either the anterior or posterior pole of the oocyte via a number of mechanisms. Many of these mRNAs are also under elaborate translational regulation. Asymmetric RNA localization coupled with spatially restricted translation ensures that their proteins are restricted to the position necessary for the developmental process that they drive. Bicoid (Bcd), the anterior determinant, and Oskar (Osk), the determinant for primordial germ cells and posterior patterning, have been studied particularly closely. In early embryos an anterior–posterior gradient of Bcd is established, activating transcription of different sets of zygotic genes depending on local Bcd concentration. At the posterior pole, Osk seeds formation of polar granules, ribonucleoprotein complexes that accumulate further mRNAs and proteins involved in posterior patterning and germ cell specification. After fertilization, polar granules associate with posterior nuclei and mature into nuclear germ granules. Osk accumulates in these granules, and either by itself or as part of the granules, stimulates germ cell division. This article is categorized under:RNA Export and Localization > RNA Localization Translation > Translation Regulation RNA in Disease and Development > RNA in Development
Collapse
Affiliation(s)
- Paul Lasko
- Department of Biology, McGill University, Montréal, Québec, Canada.,Department of Human Genetics, Radboudumc, Nijmegen, Netherlands
| |
Collapse
|
12
|
Lee YM, Chiang PH, Cheng JH, Shen WH, Chen CH, Wu ML, Tian YL, Ni CH, Wang TF, Lin MD, Chou TB. Drosophila decapping protein 2 modulates the formation of cortical F-actin for germ plasm assembly. Dev Biol 2020; 461:96-106. [PMID: 32007453 DOI: 10.1016/j.ydbio.2020.01.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2019] [Revised: 01/20/2020] [Accepted: 01/28/2020] [Indexed: 10/25/2022]
Abstract
In Drosophila, the deposition of the germ plasm at the posterior pole of the oocyte is essential for the abdomen and germ cell formation during embryogenesis. To assemble the germ plasm, oskar (osk) mRNA, produced by nurse cells, should be localized and anchored on the posterior cortex of the oocyte. Processing bodies (P-bodies) are cytoplasmic RNA granules responsible for the 5'-3' mRNA degradation. Evidence suggests that the components of P-bodies, such as Drosophila decapping protein 1 and Ge-1, are involved in the posterior localization of osk. However, whether the decapping core enzyme, Drosophila decapping protein 2 (dDcp2), is also involved remains unclear. Herein, we generated a dDcp2 null allele and showed that dDcp2 was required for the posterior localization of germ plasm components including osk. dDcp2 was distributed on the oocyte cortex and was localized posterior to the osk. In the posterior pole of dDcp2 mutant oocytes, osk was mislocalized and colocalized with F-actin detached from the cortex; moreover, considerably fewer F-actin projections were observed. Using the F-actin cosedimentation assay, we proved that dDcp2 interacted with F-actin through its middle region. In conclusion, our findings explored a novel function of dDcp2 in assisting osk localization by modulating the formation of F-actin projections on the posterior cortex.
Collapse
Affiliation(s)
- Yi-Mei Lee
- Institute of Molecular and Cellular Biology, College of Life Sciences, National Taiwan University, No.1, Sec.4, Roosevelt Rd, Taipei, 10617, Taiwan
| | - Po-Hsun Chiang
- Institute of Molecular and Cellular Biology, College of Life Sciences, National Taiwan University, No.1, Sec.4, Roosevelt Rd, Taipei, 10617, Taiwan
| | - Jen-Ho Cheng
- Institute of Molecular and Cellular Biology, College of Life Sciences, National Taiwan University, No.1, Sec.4, Roosevelt Rd, Taipei, 10617, Taiwan
| | - Wei-Hong Shen
- Institute of Molecular and Cellular Biology, College of Life Sciences, National Taiwan University, No.1, Sec.4, Roosevelt Rd, Taipei, 10617, Taiwan
| | - Chao-Han Chen
- Institute of Molecular and Cellular Biology, College of Life Sciences, National Taiwan University, No.1, Sec.4, Roosevelt Rd, Taipei, 10617, Taiwan
| | - Mei-Ling Wu
- Institute of Molecular and Cellular Biology, College of Life Sciences, National Taiwan University, No.1, Sec.4, Roosevelt Rd, Taipei, 10617, Taiwan
| | - Yi-Lu Tian
- Institute of Molecular and Cellular Biology, College of Life Sciences, National Taiwan University, No.1, Sec.4, Roosevelt Rd, Taipei, 10617, Taiwan
| | - Chao-Heng Ni
- Department of Life Sciences, College of Medicine, Tzu Chi University, 701 Zhongyang Rd, Sec. 3, Hualien, 97004, Taiwan
| | - Ting-Fang Wang
- Department of Life Sciences, College of Medicine, Tzu Chi University, 701 Zhongyang Rd, Sec. 3, Hualien, 97004, Taiwan
| | - Ming-Der Lin
- Department of Life Sciences, College of Medicine, Tzu Chi University, 701 Zhongyang Rd, Sec. 3, Hualien, 97004, Taiwan; Department of Molecular Biology and Human Genetics, College of Medicine, Tzu Chi University, 701 Zhongyang Rd, Sec. 3, Hualien, 97004, Taiwan; Department of Medical Research, Hualien Tzu Chi Hospital, 707 Zhongyang Rd, Sec. 3, Hualien, 97004, Taiwan.
| | - Tze-Bin Chou
- Institute of Molecular and Cellular Biology, College of Life Sciences, National Taiwan University, No.1, Sec.4, Roosevelt Rd, Taipei, 10617, Taiwan.
| |
Collapse
|
13
|
Peglion F, Goehring NW. Switching states: dynamic remodelling of polarity complexes as a toolkit for cell polarization. Curr Opin Cell Biol 2019; 60:121-130. [PMID: 31295650 PMCID: PMC6906085 DOI: 10.1016/j.ceb.2019.05.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 05/07/2019] [Accepted: 05/11/2019] [Indexed: 02/04/2023]
Abstract
Polarity is defined by the segregation of cellular components along a defined axis. To polarize robustly, cells must be able to break symmetry and subsequently amplify these nascent asymmetries. Finally, asymmetric localization of signaling molecules must be translated into functional regulation of downstream effector pathways. Central to these behaviors are a diverse set of cell polarity networks. Within these networks, molecules exhibit varied behaviors, dynamically switching among different complexes and states, active versus inactive, bound versus unbound, immobile versus diffusive. This ability to switch dynamically between states is intimately connected to the ability of molecules to generate asymmetric patterns within cells. Focusing primarily on polarity pathways governed by the conserved PAR proteins, we discuss strategies enabled by these dynamic behaviors that are used by cells to polarize. We highlight not only how switching between states is linked to the ability of polarity proteins to localize asymmetrically, but also how cells take advantage of 'state switching' to regulate polarity in time and space.
Collapse
Affiliation(s)
- Florent Peglion
- Cell Polarity, Migration and Cancer Unit, Institut Pasteur, UMR3691 CNRS, Equipe Labellisée Ligue Contre le Cancer, F-75015, Paris, France
| | - Nathan W Goehring
- The Francis Crick Institute, London, UK; MRC Laboratory for Molecular Cell Biology, UCL, London, UK.
| |
Collapse
|
14
|
Trcek T, Lehmann R. Germ granules in Drosophila. Traffic 2019; 20:650-660. [PMID: 31218815 PMCID: PMC6771631 DOI: 10.1111/tra.12674] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 05/26/2019] [Accepted: 06/14/2019] [Indexed: 12/22/2022]
Abstract
Germ granules are hallmarks of all germ cells. Early ultrastructural studies in Drosophila first described these membraneless granules in the oocyte and early embryo as filled with amorphous to fibrillar material mixed with RNA. Genetic studies identified key protein components and specific mRNAs that regulate germ cell‐specific functions. More recently these ultrastructural studies have been complemented by biophysical analysis describing germ granules as phase‐transitioned condensates. In this review, we provide an overview that connects the composition of germ granules with their function in controlling germ cell specification, formation and migration, and illuminate these mysterious condensates as the gatekeepers of the next generation.
Collapse
Affiliation(s)
- Tatjana Trcek
- HHMI, Skirball Institute of Biomolecular Medicine, Department of Cell Biology, NYU School of Medicine, New York, New York
| | - Ruth Lehmann
- HHMI, Skirball Institute of Biomolecular Medicine, Department of Cell Biology, NYU School of Medicine, New York, New York
| |
Collapse
|
15
|
Jouette J, Guichet A, Claret SB. Dynein-mediated transport and membrane trafficking control PAR3 polarised distribution. eLife 2019; 8:40212. [PMID: 30672465 PMCID: PMC6358217 DOI: 10.7554/elife.40212] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 01/03/2019] [Indexed: 12/14/2022] Open
Abstract
The scaffold protein PAR3 and the kinase PAR1 are essential proteins that control cell polarity. Their precise opposite localisations define plasma membrane domains with specific functions. PAR3 and PAR1 are mutually inhibited by direct or indirect phosphorylations, but their fates once phosphorylated are poorly known. Through precise spatiotemporal quantification of PAR3 localisation in the Drosophila oocyte, we identify several mechanisms responsible for its anterior cortex accumulation and its posterior exclusion. We show that PAR3 posterior plasma membrane exclusion depends on PAR1 and an endocytic mechanism relying on RAB5 and PI(4,5)P2. In a second phase, microtubules and the dynein motor, in connection with vesicular trafficking involving RAB11 and IKK-related kinase, IKKε, are required for PAR3 transport towards the anterior cortex. Altogether, our results point to a connection between membrane trafficking and dynein-mediated transport to sustain PAR3 asymmetry.
Collapse
Affiliation(s)
- Julie Jouette
- Institut Jacques Monod, CNRS, UMR 7592, Paris Diderot University, Sorbonne Paris Cité, Paris, France
| | - Antoine Guichet
- Institut Jacques Monod, CNRS, UMR 7592, Paris Diderot University, Sorbonne Paris Cité, Paris, France
| | - Sandra B Claret
- Institut Jacques Monod, CNRS, UMR 7592, Paris Diderot University, Sorbonne Paris Cité, Paris, France
| |
Collapse
|
16
|
Ciocanel MV, Sandstede B, Jeschonek SP, Mowry KL. Modeling microtubule-based transport and anchoring of mRNA. SIAM JOURNAL ON APPLIED DYNAMICAL SYSTEMS 2018; 17:2855-2881. [PMID: 34135697 PMCID: PMC8205424 DOI: 10.1137/18m1186083] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Localization of messenger RNA (mRNA) at the vegetal cortex plays an important role in the early development of Xenopus laevis oocytes. While it is known that molecular motors are responsible for the transport of mRNA cargo along microtubules to the cortex, the mechanisms of localization remain unclear. We model cargo transport along microtubules using partial differential equations with spatially-dependent rates. A theoretical analysis of reduced versions of our model predicts effective velocity and diffusion rates for the cargo and shows that randomness of microtubule networks enhances effective transport. A more complex model using parameters estimated from fluorescence microscopy data reproduces the spatial and timescales of mRNA localization observed in Xenopus oocytes, corroborates experimental hypotheses that anchoring may be necessary to achieve complete localization, and shows that anchoring of mRNA complexes actively transported to the cortex is most effective in achieving robust accumulation at the cortex.
Collapse
Affiliation(s)
| | - Björn Sandstede
- Division of Applied Mathematics, Brown University, Providence, RI
| | - Samantha P Jeschonek
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI
| | - Kimberly L Mowry
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI
| |
Collapse
|
17
|
Subcellular Specialization and Organelle Behavior in Germ Cells. Genetics 2018; 208:19-51. [PMID: 29301947 DOI: 10.1534/genetics.117.300184] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2016] [Accepted: 08/17/2017] [Indexed: 11/18/2022] Open
Abstract
Gametes, eggs and sperm, are the highly specialized cell types on which the development of new life solely depends. Although all cells share essential organelles, such as the ER (endoplasmic reticulum), Golgi, mitochondria, and centrosomes, germ cells display unique regulation and behavior of organelles during gametogenesis. These germ cell-specific functions of organelles serve critical roles in successful gamete production. In this chapter, I will review the behaviors and roles of organelles during germ cell differentiation.
Collapse
|
18
|
Lu W, Lakonishok M, Serpinskaya AS, Kirchenbüechler D, Ling SC, Gelfand VI. Ooplasmic flow cooperates with transport and anchorage in Drosophila oocyte posterior determination. J Cell Biol 2018; 217:3497-3511. [PMID: 30037924 PMCID: PMC6168253 DOI: 10.1083/jcb.201709174] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 03/27/2018] [Accepted: 07/03/2018] [Indexed: 12/21/2022] Open
Abstract
The posterior determination of the Drosophila melanogaster embryo is defined by the posterior localization of oskar (osk) mRNA in the oocyte. Defects of its localization result in a lack of germ cells and failure of abdomen specification. A microtubule motor kinesin-1 is essential for osk mRNA posterior localization. Because kinesin-1 is required for two essential functions in the oocyte-transport along microtubules and cytoplasmic streaming-it is unclear how individual kinesin-1 activities contribute to the posterior determination. We examined Staufen, an RNA-binding protein that is colocalized with osk mRNA, as a proxy of posterior determination, and we used mutants that either inhibit kinesin-driven transport along microtubules or cytoplasmic streaming. We demonstrated that late-stage streaming is partially redundant with early-stage transport along microtubules for Staufen posterior localization. Additionally, an actin motor, myosin V, is required for the Staufen anchoring to the actin cortex. We propose a model whereby initial kinesin-driven transport, subsequent kinesin-driven streaming, and myosin V-based cortical retention cooperate in posterior determination.
Collapse
Affiliation(s)
- Wen Lu
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL
| | - Margot Lakonishok
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL
| | - Anna S Serpinskaya
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL
| | - David Kirchenbüechler
- Center for Advanced Microscopy and the Nikon Imaging Center, Feinberg School of Medicine, Northwestern University, Chicago, IL
| | - Shuo-Chien Ling
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Program in Neuroscience and Behavior Disorders, Duke-National University of Singapore Medical School, Singapore
| | - Vladimir I Gelfand
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL
| |
Collapse
|
19
|
Kistler KE, Trcek T, Hurd TR, Chen R, Liang FX, Sall J, Kato M, Lehmann R. Phase transitioned nuclear Oskar promotes cell division of Drosophila primordial germ cells. eLife 2018; 7:37949. [PMID: 30260314 PMCID: PMC6191285 DOI: 10.7554/elife.37949] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Accepted: 09/09/2018] [Indexed: 12/25/2022] Open
Abstract
Germ granules are non-membranous ribonucleoprotein granules deemed the hubs for post-transcriptional gene regulation and functionally linked to germ cell fate across species. Little is known about the physical properties of germ granules and how these relate to germ cell function. Here we study two types of germ granules in the Drosophila embryo: cytoplasmic germ granules that instruct primordial germ cells (PGCs) formation and nuclear germ granules within early PGCs with unknown function. We show that cytoplasmic and nuclear germ granules are phase transitioned condensates nucleated by Oskar protein that display liquid as well as hydrogel-like properties. Focusing on nuclear granules, we find that Oskar drives their formation in heterologous cell systems. Multiple, independent Oskar protein domains synergize to promote granule phase separation. Deletion of Oskar’s nuclear localization sequence specifically ablates nuclear granules in cell systems. In the embryo, nuclear germ granules promote germ cell divisions thereby increasing PGC number for the next generation.
Collapse
Affiliation(s)
- Kathryn E Kistler
- Skirball Institute of Biomolecular Medicine, Howard Hughes Medical Institute, NYU School of Medicine, New York, United States.,Department of Molecular and Cellular Biology, University of Washington, Washington, United States
| | - Tatjana Trcek
- Skirball Institute of Biomolecular Medicine, Howard Hughes Medical Institute, NYU School of Medicine, New York, United States
| | - Thomas R Hurd
- Skirball Institute of Biomolecular Medicine, Howard Hughes Medical Institute, NYU School of Medicine, New York, United States.,Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Ruoyu Chen
- Skirball Institute of Biomolecular Medicine, Howard Hughes Medical Institute, NYU School of Medicine, New York, United States
| | - Feng-Xia Liang
- Department of Cell Biology, NYU School of Medicine, New York, United States.,DART Microscopy Laboratory, NYU Langone Health, New York, United States
| | - Joseph Sall
- DART Microscopy Laboratory, NYU Langone Health, New York, United States
| | - Masato Kato
- Department of Biochemistry, University of Texas Southwestern Medical Center, Texas, United States
| | - Ruth Lehmann
- Skirball Institute of Biomolecular Medicine, Howard Hughes Medical Institute, NYU School of Medicine, New York, United States.,Department of Cell Biology, NYU School of Medicine, New York, United States
| |
Collapse
|
20
|
Stochastic Seeding Coupled with mRNA Self-Recruitment Generates Heterogeneous Drosophila Germ Granules. Curr Biol 2018; 28:1872-1881.e3. [PMID: 29861136 DOI: 10.1016/j.cub.2018.04.037] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 03/27/2018] [Accepted: 04/12/2018] [Indexed: 11/22/2022]
Abstract
The formation of ribonucleoprotein assemblies called germ granules is a conserved feature of germline development. In Drosophila, germ granules form at the posterior of the oocyte in a specialized cytoplasm called the germ plasm, which specifies germline fate during embryogenesis. mRNAs, including nanos (nos) and polar granule component (pgc), that function in germline development are localized to the germ plasm through their incorporation into germ granules, which deliver them to the primordial germ cells. Germ granules are nucleated by Oskar (Osk) protein and contain varying combinations and quantities of their constituent mRNAs, which are organized as spatially distinct, multi-copy homotypic clusters. The process that gives rise to such heterogeneous yet organized granules remains unknown. Here, we show that individual nos and pgc transcripts can populate the same nascent granule, and these first transcripts then act as seeds, recruiting additional like transcripts to form homotypic clusters. Within a granule, homotypic clusters grow independently of each other but depend on the simultaneous acquisition of additional Osk. Although granules can contain multiple clusters of a particular mRNA, granule mRNA content is dominated by cluster size. These results suggest that the accumulation of mRNAs in the germ plasm is controlled by the mRNAs themselves through their ability to form homotypic clusters; thus, RNA self-association drives germ granule mRNA localization. We propose that a stochastic seeding and self-recruitment mechanism enables granules to simultaneously incorporate many different mRNAs while ensuring that each becomes enriched to a functional threshold.
Collapse
|
21
|
Jankovics F, Bence M, Sinka R, Faragó A, Bodai L, Pettkó-Szandtner A, Ibrahim K, Takács Z, Szarka-Kovács AB, Erdélyi M. Drosophila small ovary gene is required for transposon silencing and heterochromatin organisation and ensures germline stem cell maintenance and differentiation. Development 2018; 145:dev.170639. [DOI: 10.1242/dev.170639] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 10/29/2018] [Indexed: 12/17/2022]
Abstract
Self-renewal and differentiation of stem cells is one of the fundamental biological phenomena relying on proper chromatin organisation. In our study, we describe a novel chromatin regulator encoded by the Drosophila small ovary (sov) gene. We demonstrate that sov is required in both the germline stem cells (GSCs) and the surrounding somatic niche cells to ensure GSC survival and differentiation. Sov maintains niche integrity and function by repressing transposon mobility, not only in the germline, but also in the soma. Protein interactome analysis of Sov revealed an interaction between Sov and HP1a. In the germ cell nuclei, Sov co-localises with HP1a, suggesting that Sov affects transposon repression as a component of the heterochromatin. In a position effect variegation assay, we found a dominant genetic interaction between sov and HP1a, indicating their functional cooperation in promoting the spread of heterochromatin. An in vivo tethering assay and FRAP analysis revealed that Sov enhances heterochromatin formation by supporting the recruitment of HP1a to the chromatin. We propose a model in which sov maintains GSC niche integrity by regulating transposon silencing and heterochromatin formation.
Collapse
Affiliation(s)
- Ferenc Jankovics
- Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Melinda Bence
- Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Rita Sinka
- Department of Genetics, University of Szeged, Szeged, Hungary
| | - Anikó Faragó
- Department of Biochemistry and Molecular Biology, University of Szeged, Szeged, Hungary
| | - László Bodai
- Department of Biochemistry and Molecular Biology, University of Szeged, Szeged, Hungary
| | - Aladár Pettkó-Szandtner
- Institute of Plant Biology, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Karam Ibrahim
- Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Zsanett Takács
- Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | | | - Miklós Erdélyi
- Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| |
Collapse
|
22
|
Bilinski SM, Jaglarz MK, Tworzydlo W. The Pole (Germ) Plasm in Insect Oocytes. Results Probl Cell Differ 2017; 63:103-126. [PMID: 28779315 DOI: 10.1007/978-3-319-60855-6_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Animal germline cells are specified either through zygotic induction or cytoplasmic inheritance. Zygotic induction takes place in mid- or late embryogenesis and requires cell-to-cell signaling leading to the acquisition of germline fate de novo. In contrast, cytoplasmic inheritance involves formation of a specific, asymmetrically localized oocyte region, termed the germ (pole) plasm. This region contains maternally provided germline determinants (mRNAs, proteins) that are capable of inducing germline fate in a subset of embryonic cells. Recent data indicate that among insects, the zygotic induction represents an ancestral condition, while the cytoplasmic inheritance evolved at the base of Holometabola or in the last common ancestor of Holometabola and its sister taxon, Paraneoptera.In this chapter, we first describe subsequent stages of morphogenesis of the pole plasm and polar granules in the model organism, Drosophila melanogaster. Then, we present an overview of morphology and cytoarchitecture of the pole plasm in various holometabolan and paraneopteran insect species. Finally, we focus on phylogenetic hypotheses explaining the known distribution of two different strategies of germline specification among insects.
Collapse
Affiliation(s)
- Szczepan M Bilinski
- Department of Developmental Biology and Morphology of Invertebrates, Institute of Zoology and Biomedical Research, Jagiellonian University, Gronostajowa 9, 30-387, Krakow, Poland.
| | - Mariusz K Jaglarz
- Department of Developmental Biology and Morphology of Invertebrates, Institute of Zoology and Biomedical Research, Jagiellonian University, Gronostajowa 9, 30-387, Krakow, Poland
| | - Waclaw Tworzydlo
- Department of Developmental Biology and Morphology of Invertebrates, Institute of Zoology and Biomedical Research, Jagiellonian University, Gronostajowa 9, 30-387, Krakow, Poland
| |
Collapse
|
23
|
Abstract
Asymmetric localization of mRNAs is a widespread gene regulatory mechanism that is crucial for many cellular processes. The localization of a transcript involves multiple steps and requires several protein factors to mediate transport, anchoring and translational repression of the mRNA. Specific recognition of the localizing transcript is a key step that depends on linear or structured localization signals, which are bound by RNA-binding proteins. Genetic studies have identified many components involved in mRNA localization. However, mechanistic aspects of the pathway are still poorly understood. Here we provide an overview of structural studies that contributed to our understanding of the mechanisms underlying mRNA localization, highlighting open questions and future challenges.
Collapse
Affiliation(s)
| | - Fulvia Bono
- a Max Planck Institute for Developmental Biology , Tübingen , Germany
| |
Collapse
|
24
|
Kulkarni A, Extavour CG. Convergent evolution of germ granule nucleators: A hypothesis. Stem Cell Res 2017; 24:188-194. [PMID: 28801028 DOI: 10.1016/j.scr.2017.07.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 06/18/2017] [Accepted: 07/15/2017] [Indexed: 11/26/2022] Open
Abstract
Germ cells have been considered "the ultimate stem cell" because they alone, during normal development of sexually reproducing organisms, are able to give rise to all organismal cell types. Morphological descriptions of a specialized cytoplasm termed 'germ plasm' and associated electron dense ribonucleoprotein (RNP) structures called 'germ granules' within germ cells date back as early as the 1800s. Both germ plasm and germ granules are implicated in germ line specification across metazoans. However, at a molecular level, little is currently understood about the molecular mechanisms that assemble these entities in germ cells. The discovery that in some animals, the gene products of a small number of lineage-specific genes initiate the assembly (also termed nucleation) of germ granules and/or germ plasm is the first step towards facilitating a better understanding of these complex biological processes. Here, we draw on research spanning over 100years that supports the hypothesis that these nucleator genes may have evolved convergently, allowing them to perform analogous roles across animal lineages.
Collapse
Affiliation(s)
- Arpita Kulkarni
- Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA.
| | - Cassandra G Extavour
- Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA; Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA.
| |
Collapse
|
25
|
Kraft LM, Lackner LL. Mitochondrial anchors: Positioning mitochondria and more. Biochem Biophys Res Commun 2017; 500:2-8. [PMID: 28676393 DOI: 10.1016/j.bbrc.2017.06.193] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 06/30/2017] [Indexed: 01/08/2023]
Abstract
The shape and position of mitochondria are intimately connected to both mitochondrial and cellular function. Mitochondrial anchors play a central role in mitochondrial positioning by exerting spatial, temporal, and contextual control over the cellular position of the organelle. Investigations into the molecular mechanisms of mitochondrial anchoring are still in the early stages, and we are beginning to appreciate the number and variety of anchors that exist. From the insight gained thus far, it is clear that mitochondrial anchoring has functional and physiological consequences that extend beyond mitochondrial positioning to other critical cellular processes.
Collapse
Affiliation(s)
- Lauren M Kraft
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Laura L Lackner
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA.
| |
Collapse
|
26
|
Hurd TR, Herrmann B, Sauerwald J, Sanny J, Grosch M, Lehmann R. Long Oskar Controls Mitochondrial Inheritance in Drosophila melanogaster. Dev Cell 2017; 39:560-571. [PMID: 27923120 DOI: 10.1016/j.devcel.2016.11.004] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 09/21/2016] [Accepted: 11/07/2016] [Indexed: 12/11/2022]
Abstract
Inherited mtDNA mutations cause severe human disease. In most species, mitochondria are inherited maternally through mechanisms that are poorly understood. Genes that specifically control the inheritance of mitochondria in the germline are unknown. Here, we show that the long isoform of the protein Oskar regulates the maternal inheritance of mitochondria in Drosophila melanogaster. We show that, during oogenesis, mitochondria accumulate at the oocyte posterior, concurrent with the bulk streaming and churning of the oocyte cytoplasm. Long Oskar traps and maintains mitochondria at the posterior at the site of primordial germ cell (PGC) formation through an actin-dependent mechanism. Mutating long oskar strongly reduces the number of mtDNA molecules inherited by PGCs. Therefore, Long Oskar ensures germline transmission of mitochondria to the next generation. These results provide molecular insight into how mitochondria are passed from mother to offspring, as well as how they are positioned and asymmetrically partitioned within polarized cells.
Collapse
Affiliation(s)
- Thomas Ryan Hurd
- Department of Cell Biology, HHMI and Kimmel Center for Biology and Medicine of the Skirball Institute, New York University School of Medicine, New York, NY 10016, USA
| | - Beate Herrmann
- Department of Cell Biology, HHMI and Kimmel Center for Biology and Medicine of the Skirball Institute, New York University School of Medicine, New York, NY 10016, USA
| | - Julia Sauerwald
- Department of Cell Biology, HHMI and Kimmel Center for Biology and Medicine of the Skirball Institute, New York University School of Medicine, New York, NY 10016, USA
| | - Justina Sanny
- Department of Cell Biology, HHMI and Kimmel Center for Biology and Medicine of the Skirball Institute, New York University School of Medicine, New York, NY 10016, USA
| | - Markus Grosch
- Department of Cell Biology, HHMI and Kimmel Center for Biology and Medicine of the Skirball Institute, New York University School of Medicine, New York, NY 10016, USA
| | - Ruth Lehmann
- Department of Cell Biology, HHMI and Kimmel Center for Biology and Medicine of the Skirball Institute, New York University School of Medicine, New York, NY 10016, USA.
| |
Collapse
|
27
|
Jeske M, Müller CW, Ephrussi A. The LOTUS domain is a conserved DEAD-box RNA helicase regulator essential for the recruitment of Vasa to the germ plasm and nuage. Genes Dev 2017; 31:939-952. [PMID: 28536148 PMCID: PMC5458760 DOI: 10.1101/gad.297051.117] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 05/08/2017] [Indexed: 12/15/2022]
Abstract
DEAD-box RNA helicases play important roles in a wide range of metabolic processes. Regulatory proteins can stimulate or block the activity of DEAD-box helicases. Here, we show that LOTUS (Limkain, Oskar, and Tudor containing proteins 5 and 7) domains present in the germline proteins Oskar, TDRD5 (Tudor domain-containing 5), and TDRD7 bind and stimulate the germline-specific DEAD-box RNA helicase Vasa. Our crystal structure of the LOTUS domain of Oskar in complex with the C-terminal RecA-like domain of Vasa reveals that the LOTUS domain occupies a surface on a DEAD-box helicase not implicated previously in the regulation of the enzyme's activity. We show that, in vivo, the localization of Drosophila Vasa to the nuage and germ plasm depends on its interaction with LOTUS domain proteins. The binding and stimulation of Vasa DEAD-box helicases by LOTUS domains are widely conserved.
Collapse
Affiliation(s)
- Mandy Jeske
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.,Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Christoph W Müller
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| |
Collapse
|
28
|
Goldman CH, Gonsalvez GB. The Role of Microtubule Motors in mRNA Localization and Patterning Within the Drosophila Oocyte. Results Probl Cell Differ 2017; 63:149-168. [PMID: 28779317 DOI: 10.1007/978-3-319-60855-6_7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Messenger RNA (mRNA) localization is a powerful and prevalent mechanism of post-transcriptional gene regulation, enabling the cell to produce protein at the exact location at which it is needed. The phenomenon of mRNA localization has been observed in many types of cells in organisms ranging from yeast to man. Thus, the process appears to be widespread and highly conserved. Several model systems have been used to understand the mechanism by which mRNAs are localized. One such model, and the focus of this chapter, is the egg chamber of the female Drosophila melanogaster. The polarity of the developing Drosophila oocyte and resulting embryo relies on the specific localization of three critical mRNAs: gurken, bicoid, and oskar. If these mRNAs are not localized during oogenesis, the resulting progeny will not survive. The study of these mRNAs has served as a model for understanding the general mechanisms by which mRNAs are sorted. In this chapter, we will discuss how the localization of these mRNAs enables polarity establishment. We will also discuss the role of motor proteins in the localization pathway. Finally, we will consider potential mechanisms by which mRNAs can be anchored at their site of localization. It is likely that the lessons learned using the Drosophila oocyte model system will be applicable to mRNAs that are localized in other organisms as well.
Collapse
Affiliation(s)
- Chandler H Goldman
- Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1459 Laney Walker Blvd., CB2917, Augusta, GA, 30912, USA
| | - Graydon B Gonsalvez
- Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1459 Laney Walker Blvd., CB2917, Augusta, GA, 30912, USA.
| |
Collapse
|
29
|
Nieuwburg R, Nashchekin D, Jakobs M, Carter AP, Khuc Trong P, Goldstein RE, St Johnston D. Localised dynactin protects growing microtubules to deliver oskar mRNA to the posterior cortex of the Drosophila oocyte. eLife 2017; 6:e27237. [PMID: 29035202 PMCID: PMC5643094 DOI: 10.7554/elife.27237] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 09/19/2017] [Indexed: 11/13/2022] Open
Abstract
The localisation of oskar mRNA to the posterior of the Drosophila oocyte defines where the abdomen and germ cells form in the embryo. Kinesin 1 transports oskar mRNA to the oocyte posterior along a polarised microtubule cytoskeleton that grows from non-centrosomal microtubule organising centres (ncMTOCs) along the anterior/lateral cortex. Here, we show that the formation of this polarised microtubule network also requires the posterior regulation of microtubule growth. A missense mutation in the dynactin Arp1 subunit causes most oskar mRNA to localise in the posterior cytoplasm rather than cortically. oskar mRNA transport and anchoring are normal in this mutant, but the microtubules fail to reach the posterior pole. Thus, dynactin acts as an anti-catastrophe factor that extends microtubule growth posteriorly. Kinesin 1 transports dynactin to the oocyte posterior, creating a positive feedback loop that increases the length and persistence of the posterior microtubules that deliver oskar mRNA to the cortex.
Collapse
Affiliation(s)
- Ross Nieuwburg
- The Gurdon Institute and the Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
| | - Dmitry Nashchekin
- The Gurdon Institute and the Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
| | - Maximilian Jakobs
- The Department of Physiology, Development and NeuroscienceUniversity of CambridgeCambridgeUnited Kingdom
| | - Andrew P Carter
- Division of Structural StudiesMedical Research Council, Laboratory of Molecular BiologyCambridgeUnited Kingdom
| | - Philipp Khuc Trong
- Department of Applied Mathematics and Theoretical PhysicsUniversity of Cambridge, Centre for Mathematical SciencesCambridgeUnited Kingdom
| | - Raymond E Goldstein
- Department of Applied Mathematics and Theoretical PhysicsUniversity of Cambridge, Centre for Mathematical SciencesCambridgeUnited Kingdom
| | - Daniel St Johnston
- The Gurdon Institute and the Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
| |
Collapse
|
30
|
Trovisco V, Belaya K, Nashchekin D, Irion U, Sirinakis G, Butler R, Lee JJ, Gavis ER, St Johnston D. bicoid mRNA localises to the Drosophila oocyte anterior by random Dynein-mediated transport and anchoring. eLife 2016; 5. [PMID: 27791980 PMCID: PMC5125753 DOI: 10.7554/elife.17537] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 10/25/2016] [Indexed: 01/17/2023] Open
Abstract
bicoid mRNA localises to the Drosophila oocyte anterior from stage 9 of oogenesis onwards to provide a local source for Bicoid protein for embryonic patterning. Live imaging at stage 9 reveals that bicoid mRNA particles undergo rapid Dynein-dependent movements near the oocyte anterior, but with no directional bias. Furthermore, bicoid mRNA localises normally in shot2A2, which abolishes the polarised microtubule organisation. FRAP and photo-conversion experiments demonstrate that the RNA is stably anchored at the anterior, independently of microtubules. Thus, bicoid mRNA is localised by random active transport and anterior anchoring. Super-resolution imaging reveals that bicoid mRNA forms 110-120 nm particles with variable RNA content, but constant size. These particles appear to be well-defined structures that package the RNA for transport and anchoring.
Collapse
Affiliation(s)
- Vítor Trovisco
- The Gurdon Institute, University of Cambridge, Cambridge, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Katsiaryna Belaya
- The Gurdon Institute, University of Cambridge, Cambridge, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Dmitry Nashchekin
- The Gurdon Institute, University of Cambridge, Cambridge, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Uwe Irion
- The Gurdon Institute, University of Cambridge, Cambridge, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - George Sirinakis
- The Gurdon Institute, University of Cambridge, Cambridge, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Richard Butler
- The Gurdon Institute, University of Cambridge, Cambridge, United Kingdom
| | - Jack J Lee
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Elizabeth R Gavis
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Daniel St Johnston
- The Gurdon Institute, University of Cambridge, Cambridge, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| |
Collapse
|
31
|
Macdonald PM, Kanke M, Kenny A. Community effects in regulation of translation. eLife 2016; 5:e10965. [PMID: 27104756 PMCID: PMC4846370 DOI: 10.7554/elife.10965] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 03/18/2016] [Indexed: 12/27/2022] Open
Abstract
Certain forms of translational regulation, and translation itself, rely on long-range interactions between proteins bound to the different ends of mRNAs. A widespread assumption is that such interactions occur only in cis, between the two ends of a single transcript. However, certain translational regulatory defects of the Drosophila oskar (osk) mRNA can be rescued in trans. We proposed that inter-transcript interactions, promoted by assembly of the mRNAs in particles, allow regulatory elements to act in trans. Here we confirm predictions of that model and show that disruption of PTB-dependent particle assembly inhibits rescue in trans. Communication between transcripts is not limited to different osk mRNAs, as regulation imposed by cis-acting elements embedded in the osk mRNA spreads to gurken mRNA. We conclude that community effects exist in translational regulation. DOI:http://dx.doi.org/10.7554/eLife.10965.001 Genes encode the instructions needed to make proteins and other molecules. To make a protein, the DNA within a gene is copied to produce molecules of messenger ribonucleic acid (mRNA) that are then used as templates to build proteins via a process called translation. This process – which involves protein machines called ribosomes binding to the start of the mRNA – is tightly regulated to control the amounts of particular proteins in cells. For example, in fruit fly ovaries, a protein called Bruno both represses and activates the translation of a gene known as oskar. To achieve this, Bruno binds to regions near the end of the oskar RNA known as Bruno response elements. It is not clear how Bruno acts to control translation. However, because ribosomes begin translation near the start of the mRNA, while Bruno is bound to regions near the end of the mRNA, there must be long-range interactions between the two ends of the mRNA. It is generally assumed that such long-range interactions only occur between proteins that are bound to the same mRNA molecule. However, in 2010, researchers observed that Bruno response elements within one oskar mRNA could influence the translation of other oskar mRNAs. This is known as “regulation in trans”. Here, Macdonald et al. – including some of the researchers from the earlier work – investigated this observation in more detail in fruit flies. In cells, multiple mRNA molecules and their associated proteins can assemble into particles. Macdonald et al. proposed that the close proximity of many mRNA molecules in these particles could allow trans regulation to take place. Indeed, the experiments found that blocking the assembly of oskar mRNA into particles inhibited trans regulation as expected. Macdonald et al. also asked if trans regulation can occur between mRNAs that encode different proteins. The experiments show that oskar mRNA could block the translation of an mRNA produced by the gurken gene, even when oskar mRNA was not being translated. More work is needed to find out how widely trans regulation is used to control translation. DOI:http://dx.doi.org/10.7554/eLife.10965.002
Collapse
Affiliation(s)
- Paul M Macdonald
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, United States.,Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, United States
| | - Matt Kanke
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, United States.,Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, United States
| | - Andrew Kenny
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, United States.,Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, United States
| |
Collapse
|
32
|
Abstract
Germ granules are the hallmark of all germ cells. These membrane-less, electron-dense structures were first observed over 100 years ago. Today, their role in regulating and processing transcripts critical for the establishment, maintenance, and protection of germ cells is well established, and pathways outlining the biochemical mechanisms and physical properties associated with their biogenesis are emerging.
Collapse
Affiliation(s)
- Ruth Lehmann
- Howard Hughes Medical Institute (HHMI), Department of Cell Biology, Kimmel Center for Biology and Medicine of the Skirball Institute, New York University School of Medicine, New York, USA.
| |
Collapse
|
33
|
Abstract
Primordial germ cells are the progenitor cells that give rise to the gametes. In some animals, the germline is induced by zygotic transcription factors, whereas in others, primordial germ cell specification occurs via inheritance of maternally provided gene products known as germ plasm. Once specified, the primordial germ cells of some animals must acquire motility and migrate to the gonad in order to survive. In all animals examined, perinuclear structures called germ granules form within germ cells. This review focuses on some of the recent studies, conducted by several groups using diverse systems, from invertebrates to vertebrates, which have provided mechanistic insight into the molecular regulation of germ cell specification and migration.
Collapse
Affiliation(s)
- Florence Marlow
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Yeshiva University, Bronx, NY, 10461, USA; Department of Neuroscience, Albert Einstein College of Medicine, Yeshiva University, Bronx, NY, 10461, USA
| |
Collapse
|
34
|
Khuc Trong P, Doerflinger H, Dunkel J, St Johnston D, Goldstein RE. Cortical microtubule nucleation can organise the cytoskeleton of Drosophila oocytes to define the anteroposterior axis. eLife 2015; 4. [PMID: 26406117 PMCID: PMC4580948 DOI: 10.7554/elife.06088] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 08/14/2015] [Indexed: 02/02/2023] Open
Abstract
Many cells contain non-centrosomal arrays of microtubules (MTs), but the assembly, organisation and function of these arrays are poorly understood. We present the first theoretical model for the non-centrosomal MT cytoskeleton in Drosophila oocytes, in which bicoid and oskar mRNAs become localised to establish the anterior-posterior body axis. Constrained by experimental measurements, the model shows that a simple gradient of cortical MT nucleation is sufficient to reproduce the observed MT distribution, cytoplasmic flow patterns and localisation of oskar and naive bicoid mRNAs. Our simulations exclude a major role for cytoplasmic flows in localisation and reveal an organisation of the MT cytoskeleton that is more ordered than previously thought. Furthermore, modulating cortical MT nucleation induces a bifurcation in cytoskeletal organisation that accounts for the phenotypes of polarity mutants. Thus, our three-dimensional model explains many features of the MT network and highlights the importance of differential cortical MT nucleation for axis formation. DOI:http://dx.doi.org/10.7554/eLife.06088.001 Cells contain a network of filaments known as microtubules that serve as tracks along which proteins and other materials can be moved from one location to another. For example, molecules called messenger ribonucleic acids (or mRNAs for short) are made in the nucleus and are then moved to various locations around the cell. Each mRNA molecule encodes the instructions needed to make a particular protein and the network of microtubules allows these molecules to be directed to wherever these proteins are needed. In female fruit flies, an mRNA called bicoid is moved to one end (called the anterior end) of a developing egg cell, while another mRNA called oskar is moved to the opposite (posterior) end. These mRNAs determine which ends of the cell will give rise to the head and the abdomen if the egg is fertilized. The microtubules start to form at sites near the inner face of the membrane that surrounds the cell, known as the cortex. From there, the microtubules grow towards the interior of the egg cell. However, it is not clear how this allows bicoid, oskar and other mRNAs to be moved to the correct locations. Khuc Trong et al. used a combination of computational and experimental techniques to develop a model of how microtubules form in the egg cells of fruit flies. The model produces a very similar arrangement of microtubules as observed in living cells and can reproduce the patterns of bicoid and oskar RNA movements. This study suggests that microtubules are more highly organised than previously thought. Furthermore, Khuc Trong et al.'s findings indicate that the anchoring of microtubules in the cortex is sufficient to direct bicoid and oskar RNAs to the opposite ends of the cell. The next challenge will be to find out how the microtubules are linked to the cortex and how this is regulated. DOI:http://dx.doi.org/10.7554/eLife.06088.002
Collapse
Affiliation(s)
- Philipp Khuc Trong
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
| | - Hélène Doerflinger
- Wellcome Trust/Cancer Research UK Gurdon Institute, Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Cambridge, United Kingdom
| | - Jörn Dunkel
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
| | - Daniel St Johnston
- Wellcome Trust/Cancer Research UK Gurdon Institute, Henry Wellcome Building of Cancer and Developmental Biology, University of Cambridge, Cambridge, United Kingdom
| | - Raymond E Goldstein
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
| |
Collapse
|
35
|
Jeske M, Bordi M, Glatt S, Müller S, Rybin V, Müller CW, Ephrussi A. The Crystal Structure of the Drosophila Germline Inducer Oskar Identifies Two Domains with Distinct Vasa Helicase- and RNA-Binding Activities. Cell Rep 2015; 12:587-98. [PMID: 26190108 DOI: 10.1016/j.celrep.2015.06.055] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 05/25/2015] [Accepted: 06/15/2015] [Indexed: 12/31/2022] Open
Abstract
In many animals, the germ plasm segregates germline from soma during early development. Oskar protein is known for its ability to induce germ plasm formation and germ cells in Drosophila. However, the molecular basis of germ plasm formation remains unclear. Here, we show that Oskar is an RNA-binding protein in vivo, crosslinking to nanos, polar granule component, and germ cell-less mRNAs, each of which has a role in germline formation. Furthermore, we present high-resolution crystal structures of the two Oskar domains. RNA-binding maps in vitro to the C-terminal domain, which shows structural similarity to SGNH hydrolases. The highly conserved N-terminal LOTUS domain forms dimers and mediates Oskar interaction with the germline-specific RNA helicase Vasa in vitro. Our findings suggest a dual function of Oskar in RNA and Vasa binding, providing molecular clues to its germ plasm function.
Collapse
Affiliation(s)
- Mandy Jeske
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany; Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Matteo Bordi
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Sebastian Glatt
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Sandra Müller
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Vladimir Rybin
- Protein Expression and Purification Core Facility, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Christoph W Müller
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
| |
Collapse
|
36
|
Kanke M, Jambor H, Reich J, Marches B, Gstir R, Ryu YH, Ephrussi A, Macdonald PM. oskar RNA plays multiple noncoding roles to support oogenesis and maintain integrity of the germline/soma distinction. RNA (NEW YORK, N.Y.) 2015; 21:1096-109. [PMID: 25862242 PMCID: PMC4436663 DOI: 10.1261/rna.048298.114] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 02/12/2015] [Indexed: 05/05/2023]
Abstract
The Drosophila oskar (osk) mRNA is unusual in that it has both coding and noncoding functions. As an mRNA, osk encodes a protein required for embryonic patterning and germ cell formation. Independent of that function, the absence of osk mRNA disrupts formation of the karyosome and blocks progression through oogenesis. Here we show that loss of osk mRNA also affects the distribution of regulatory proteins, relaxing their association with large RNPs within the germline, and allowing them to accumulate in the somatic follicle cells. This and other noncoding functions of the osk mRNA are mediated by multiple sequence elements with distinct roles. One role, provided by numerous binding sites in two distinct regions of the osk 3' UTR, is to sequester the translational regulator Bruno (Bru), which itself controls translation of osk mRNA. This defines a novel regulatory circuit, with Bru restricting the activity of osk, and osk in turn restricting the activity of Bru. Other functional elements, which do not bind Bru and are positioned close to the 3' end of the RNA, act in the oocyte and are essential. Despite the different roles played by the different types of elements contributing to RNA function, mutation of any leads to accumulation of the germline regulatory factors in the follicle cells.
Collapse
Affiliation(s)
- Matt Kanke
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Helena Jambor
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - John Reich
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Brittany Marches
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Ronald Gstir
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Young Hee Ryu
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Paul M Macdonald
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
| |
Collapse
|
37
|
Kanke M, Macdonald PM. Translational activation of oskar mRNA: reevaluation of the role and importance of a 5' regulatory element [corrected]. PLoS One 2015; 10:e0125849. [PMID: 25938537 PMCID: PMC4418564 DOI: 10.1371/journal.pone.0125849] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Accepted: 03/24/2015] [Indexed: 01/17/2023] Open
Abstract
Local translation of oskar (osk) mRNA at the posterior pole of the Drosophila oocyte is essential for axial patterning of the embryo, and is achieved by a program of translational repression, mRNA localization, and translational activation. Multiple forms of repression are used to prevent Oskar protein from accumulating at sites other than the oocyte posterior. Activation is mediated by several types of cis-acting elements, which presumably control different forms of activation. We characterize a 5' element, positioned in the coding region for the Long Osk isoform and in the extended 5' UTR for translation of the Short Osk isoform. This element was previously thought to be essential for osk mRNA translation, with a role in posterior-specific release from repression. From our work, which includes assays which separate the effects of mutations on RNA regulatory elements and protein coding capacity, we find that the element is not essential, and conclude that there is no evidence supporting a role for the element only at the posterior of the oocyte. The 5' element has a redundant role, and is only required when Long Osk is not translated from the same mRNA. Mutations in the element do disrupt the anchoring function of Long Osk protein through their effects on the amino acid sequence, a confounding influence on interpretation of previous experiments.
Collapse
Affiliation(s)
- Matt Kanke
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, United States of America
| | - Paul M. Macdonald
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, United States of America
- * E-mail:
| |
Collapse
|
38
|
Halstead JM, Lionnet T, Wilbertz JH, Wippich F, Ephrussi A, Singer RH, Chao JA. Translation. An RNA biosensor for imaging the first round of translation from single cells to living animals. Science 2015; 347:1367-671. [PMID: 25792328 DOI: 10.1126/science.aaa3380] [Citation(s) in RCA: 198] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Analysis of single molecules in living cells has provided quantitative insights into the kinetics of fundamental biological processes; however, the dynamics of messenger RNA (mRNA) translation have yet to be addressed. We have developed a fluorescence microscopy technique that reports on the first translation events of individual mRNA molecules. This allowed us to examine the spatiotemporal regulation of translation during normal growth and stress and during Drosophila oocyte development. We have shown that mRNAs are not translated in the nucleus but translate within minutes after export, that sequestration within P-bodies regulates translation, and that oskar mRNA is not translated until it reaches the posterior pole of the oocyte. This methodology provides a framework for studying initiation of protein synthesis on single mRNAs in living cells.
Collapse
Affiliation(s)
- James M Halstead
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland
| | - Timothée Lionnet
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA. Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA. Transcription Imaging Consortium, Howard Hughes Medical Institute Janelia Farm Research Campus, Ashburn, VA 20147, USA
| | - Johannes H Wilbertz
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland. University of Basel, CH-4003 Basel, Switzerland
| | - Frank Wippich
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
| | - Robert H Singer
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA. Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA. Transcription Imaging Consortium, Howard Hughes Medical Institute Janelia Farm Research Campus, Ashburn, VA 20147, USA.
| | - Jeffrey A Chao
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland. Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| |
Collapse
|
39
|
Little SC, Sinsimer KS, Lee JJ, Wieschaus EF, Gavis ER. Independent and coordinate trafficking of single Drosophila germ plasm mRNAs. Nat Cell Biol 2015; 17:558-68. [PMID: 25848747 PMCID: PMC4417036 DOI: 10.1038/ncb3143] [Citation(s) in RCA: 119] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 02/20/2015] [Indexed: 11/24/2022]
Abstract
mRNA localization is a conserved mechanism for spatial control of protein synthesis, with key roles in generating cellular and developmental asymmetry. While different transcripts may be targeted to the same subcellular domain, the extent to which their localization is coordinated is unclear. Using quantitative single molecule imaging, we analyzed the assembly of Drosophila germ plasm mRNA granules inherited by nascent germ cells. We find that the germ cell-destined transcripts nanos, cyclin B, and polar granule component travel within the oocyte as ribonucleoprotein particles containing single mRNA molecules but co-assemble into multi-copy heterogeneous granules selectively at the posterior of the oocyte. The stoichiometry and dynamics of assembly indicate a defined stepwise sequence. Our data suggest that co-packaging of these transcripts ensures their effective segregation to germ cells. In contrast, compartmentalization of the germline determinant oskar mRNA into different granules limits its entry into germ cells. This exclusion is required for proper germline development.
Collapse
Affiliation(s)
- Shawn C Little
- 1] Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA [2] Howard Hughes Medical Institute, Princeton University, Princeton, New Jersey 08544, USA
| | - Kristina S Sinsimer
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
| | - Jack J Lee
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
| | - Eric F Wieschaus
- 1] Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA [2] Howard Hughes Medical Institute, Princeton University, Princeton, New Jersey 08544, USA
| | - Elizabeth R Gavis
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
| |
Collapse
|
40
|
Jambor H, Surendranath V, Kalinka AT, Mejstrik P, Saalfeld S, Tomancak P. Systematic imaging reveals features and changing localization of mRNAs in Drosophila development. eLife 2015; 4. [PMID: 25838129 PMCID: PMC4384636 DOI: 10.7554/elife.05003] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2014] [Accepted: 03/09/2015] [Indexed: 01/02/2023] Open
Abstract
mRNA localization is critical for eukaryotic cells and affects numerous transcripts, yet how cells regulate distribution of many mRNAs to their subcellular destinations is still unknown. We combined transcriptomics and systematic imaging to determine the tissue-specific expression and subcellular distribution of 5862 mRNAs during Drosophila oogenesis. mRNA localization is widespread in the ovary and detectable in all of its cell types—the somatic epithelial, the nurse cells, and the oocyte. Genes defined by a common RNA localization share distinct gene features and differ in expression level, 3′UTR length and sequence conservation from unlocalized mRNAs. Comparison of mRNA localizations in different contexts revealed that localization of individual mRNAs changes over time in the oocyte and between ovarian and embryonic cell types. This genome scale image-based resource (Dresden Ovary Table, DOT, http://tomancak-srv1.mpi-cbg.de/DOT/main.html) enables the transition from mechanistic dissection of singular mRNA localization events towards global understanding of how mRNAs transcribed in the nucleus distribute in cells. DOI:http://dx.doi.org/10.7554/eLife.05003.001 To make a protein, the DNA sequence that encodes it must first be ‘transcribed’ to build a molecule of messenger RNA (called mRNA for short). Although many mRNA molecules are found throughout a cell, some are ‘localized’ to certain areas; and recent evidence suggests that this mRNA localization may be more common than previously thought. Not much is known about how cells identify which mRNAs need to be localized, or how these molecules are then transported to their destination. The localization process has been studied in most detail in the developing egg cell—also known as an oocyte—of the fruit fly species Drosophila melanogaster. These studies have identified few mRNA molecules that, if they are not carefully localized within the cell, cause the different parts of the fly embryo to fail to develop correctly when the oocyte is fertilized. Jambor et al. created an open-access online resource called the ‘Dresden Ovary Table’ that shows how 5862 mRNA molecules are distributed in several cell types involved in oocyte production in the ovary of female D. melanogaster flies. This resource consists of a combination of three-dimensional fluorescent images and measurements of mRNA amounts recorded at different stages in the development of the oocyte. Using the resource, Jambor et al. demonstrate that all of the cell types that make up the ovary localize many different mRNA molecules to several distinct destinations within the cells. The localized mRNAs share certain features, with mRNAs localized in the same part of the cell showing the most similarities. For example, localized mRNAs have longer so-called 3′ untranslated regions (3′UTR) that carry regulatory information and these sequences are also more evolutionarily conserved. Further, when the mRNA molecules in the oocyte were examined at different times during its development and compared with the embryo, the majority of these mRNAs were found to change where they are localized as the organism develops. The resource can be used to gain insight into specific genetic features that control the distribution of mRNAs. This information will be instrumental for cracking the ‘RNA localization code’ and understanding how it affects the activity of proteins in cells. DOI:http://dx.doi.org/10.7554/eLife.05003.002
Collapse
Affiliation(s)
- Helena Jambor
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | | | - Alex T Kalinka
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Pavel Mejstrik
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Stephan Saalfeld
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Pavel Tomancak
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| |
Collapse
|
41
|
Kim G, Pai CI, Sato K, Person MD, Nakamura A, Macdonald PM. Region-specific activation of oskar mRNA translation by inhibition of Bruno-mediated repression. PLoS Genet 2015; 11:e1004992. [PMID: 25723530 PMCID: PMC4344327 DOI: 10.1371/journal.pgen.1004992] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 01/07/2015] [Indexed: 11/18/2022] Open
Abstract
A complex program of translational repression, mRNA localization, and translational activation ensures that Oskar (Osk) protein accumulates only at the posterior pole of the Drosophila oocyte. Inappropriate expression of Osk disrupts embryonic axial patterning, and is lethal. A key factor in translational repression is Bruno (Bru), which binds to regulatory elements in the osk mRNA 3' UTR. After posterior localization of osk mRNA, repression by Bru must be alleviated. Here we describe an in vivo assay system to monitor the spatial pattern of Bru-dependent repression, separate from the full complexity of osk regulation. This assay reveals a form of translational activation-region-specific activation-which acts regionally in the oocyte, is not mechanistically coupled to mRNA localization, and functions by inhibiting repression by Bru. We also show that Bru dimerizes and identify mutations that disrupt this interaction to test its role in vivo. Loss of dimerization does not disrupt repression, as might have been expected from an existing model for the mechanism of repression. However, loss of dimerization does impair regional activation of translation, suggesting that dimerization may constrain, not promote, repression. Our work provides new insight into the question of how localized mRNAs become translationally active, showing that repression of osk mRNA is locally inactivated by a mechanism acting independent of mRNA localization.
Collapse
Affiliation(s)
- Goheun Kim
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, United States of America
| | - Chin-I Pai
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, United States of America
| | - Keiji Sato
- Laboratory for Germline Development, RIKEN Center for Developmental Biology, Kobe, Hyogo, Japan
| | - Maria D. Person
- Proteomics Facility, Institute for Cellular and Molecular Biology and College of Pharmacy, The University of Texas at Austin, Austin, Texas, United States of America
| | - Akira Nakamura
- Department of Germline Development, Division of Organogenesis, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto, Japan
| | - Paul M. Macdonald
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, United States of America
- * E-mail:
| |
Collapse
|
42
|
Abstract
The Drosophila melanogaster ovary has served as a popular and successful model for understanding a wide range of biological processes: stem cell function, germ cell development, meiosis, cell migration, morphogenesis, cell death, intercellular signaling, mRNA localization, and translational control. This review provides a brief introduction to Drosophila oogenesis, along with a survey of its diverse biological topics and the advanced genetic tools that continue to make this a popular developmental model system.
Collapse
|
43
|
Tanaka T, Nakamura A. Oskar-induced endocytic activation and actin remodeling for anchorage of the Drosophila germ plasm. BIOARCHITECTURE 2014; 1:122-126. [PMID: 21922042 DOI: 10.4161/bioa.1.3.17313] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Accepted: 07/13/2011] [Indexed: 12/29/2022]
Abstract
In many animals, germ-cell fate is specified by inheritance of the germ plasm, which is enriched in maternal RNAs and proteins. Assembly of the Drosophila germ (pole) plasm begins with the localization and translation of oskar (osk) RNA at the oocyte posterior pole. osk RNA produces two isoforms, long and short Osk. Short Osk recruits other pole plasm components, and long Osk restricts them to the oocyte cortex. Although molecular functions of long Osk remain mysterious, it is known to be involved in endocytic activation and actin cytoskeletal remodeling. We identified several vesicular trafficking machinery components that act downstream of long Osk in pole plasm assembly. These included the Rab5 effector protein Rabenosyn-5 (Rbsn-5) and the Golgi/endosomal protein Mon2, both of which were crucial for Osk-induced actin remodeling and the anchoring of pole plasm components. We propose that, in response to long Osk, the Rab5/Rbsn-5-dependent endocytic pathway promotes the formation of specialized vesicles, and Mon2 acts on these vesicles as a scaffold to instruct actin nucleators like Cappuccino and Spire to remodel the actin cytoskeleton, which anchors pole plasm components to the cortex. This mechanism may be applicable to the asymmetric localization of macromolecular structures such as protein-RNA complexes in other systems.
Collapse
Affiliation(s)
- Tsubasa Tanaka
- Laboratory for Germline Development; RIKEN Center for Developmental Biology; Kobe; Hyogo, Japan
| | | |
Collapse
|
44
|
Gaspar I, Yu YV, Cotton SL, Kim DH, Ephrussi A, Welte MA. Klar ensures thermal robustness of oskar localization by restraining RNP motility. ACTA ACUST UNITED AC 2014; 206:199-215. [PMID: 25049271 PMCID: PMC4107779 DOI: 10.1083/jcb.201310010] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
When temperature fluctuation threatens the fidelity of Drosophila oogenesis, Klar restrains posterior-ward translocation of oskar mRNA, thereby adapting the rate of oskar delivery to the capacity of the anchoring machinery. Communication usually applies feedback loop–based filters and amplifiers to ensure undistorted delivery of messages. Such an amplifier acts during Drosophila melanogaster midoogenesis, when oskar messenger ribonucleic acid (mRNA) anchoring depends on its own locally translated protein product. We find that the motor regulator Klar β mediates a gain-control process that prevents saturation-based distortions in this positive feedback loop. We demonstrate that, like oskar mRNA, Klar β localizes to the posterior pole of oocytes in a kinesin-1–dependent manner. By live imaging and semiquantitative fluorescent in situ hybridization, we show that Klar β restrains oskar ribonucleoprotein motility and decreases the posterior-ward translocation of oskar mRNA, thereby adapting the rate of oskar delivery to the output of the anchoring machinery. This negative regulatory effect of Klar is particularly important for overriding temperature-induced changes in motility. We conclude that by preventing defects in oskar anchoring, this mechanism contributes to the developmental robustness of a poikilothermic organism living in a variable temperature environment.
Collapse
Affiliation(s)
- Imre Gaspar
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Yanxun V Yu
- Department of Biology, University of Rochester, Rochester, NY 14627
| | - Sean L Cotton
- Department of Biology, Brandeis University, Waltham, MA 02454
| | - Dae-Hwan Kim
- Department of Biology, Brandeis University, Waltham, MA 02454
| | - Anne Ephrussi
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Michael A Welte
- Department of Biology, University of Rochester, Rochester, NY 14627 Department of Biology, Brandeis University, Waltham, MA 02454
| |
Collapse
|
45
|
Vazquez-Pianzola P, Adam J, Haldemann D, Hain D, Urlaub H, Suter B. Clathrin heavy chain plays multiple roles in polarizing the Drosophila oocyte downstream of Bic-D. Development 2014; 141:1915-26. [PMID: 24718986 DOI: 10.1242/dev.099432] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Bicaudal-D (Bic-D), Egalitarian (Egl), microtubules and their motors form a transport machinery that localizes a remarkable diversity of mRNAs to specific cellular regions during oogenesis and embryogenesis. Bic-D family proteins also promote dynein-dependent transport of Golgi vesicles, lipid droplets, synaptic vesicles and nuclei. However, the transport of these different cargoes is still poorly understood. We searched for novel proteins that either mediate Bic-D-dependent transport processes or are transported by them. Clathrin heavy chain (Chc) co-immunopurifies with Bic-D in embryos and ovaries, and a fraction of Chc colocalizes with Bic-D. Both proteins control posterior patterning of the Drosophila oocyte and endocytosis. Although the role of Chc in endocytosis is well established, our results show that Bic-D is also needed for the elevated endocytic activity at the posterior of the oocyte. Apart from affecting endocytosis indirectly by its role in osk mRNA localization, Bic-D is also required to transport Chc mRNA into the oocyte and for transport and proper localization of Chc protein to the oocyte cortex, pointing to an additional, more direct role of Bic-D in the endocytic pathway. Furthermore, similar to Bic-D, Chc also contributes to proper localization of osk mRNA and to oocyte growth. However, in contrast to other endocytic components and factors of the endocytic recycling pathway, such as Rabenosyn-5 (Rbsn-5) and Rab11, Chc is needed during early stages of oogenesis (from stage 6 onwards) to localize osk mRNA correctly. Moreover, we also uncovered a novel, presumably endocytosis-independent, role of Chc in the establishment of microtubule polarity in stage 6 oocytes.
Collapse
|
46
|
Jambor H, Mueller S, Bullock SL, Ephrussi A. A stem-loop structure directs oskar mRNA to microtubule minus ends. RNA (NEW YORK, N.Y.) 2014; 20:429-39. [PMID: 24572808 PMCID: PMC3964905 DOI: 10.1261/rna.041566.113] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Accepted: 01/06/2014] [Indexed: 05/22/2023]
Abstract
mRNA transport coupled with translational control underlies the intracellular localization of many proteins in eukaryotic cells. This is exemplified in Drosophila, where oskar mRNA transport and translation at the posterior pole of the oocyte direct posterior patterning of the embryo. oskar localization is a multistep process. Within the oocyte, a spliced oskar localization element (SOLE) targets oskar mRNA for plus end-directed transport by kinesin-1 to the posterior pole. However, the signals mediating the initial minus end-directed, dynein-dependent transport of the mRNA from nurse cells into the oocyte have remained unknown. Here, we show that a 67-nt stem-loop in the oskar 3' UTR promotes oskar mRNA delivery to the developing oocyte and that it shares functional features with the fs(1)K10 oocyte localization signal. Thus, two independent cis-acting signals, the oocyte entry signal (OES) and the SOLE, mediate sequential dynein- and kinesin-dependent phases of oskar mRNA transport during oogenesis. The OES also promotes apical localization of injected RNAs in blastoderm stage embryos, another dynein-mediated process. Similarly, when ectopically expressed in polarized cells of the follicular epithelium or salivary glands, reporter RNAs bearing the oskar OES are apically enriched, demonstrating that this element promotes mRNA localization independently of cell type. Our work sheds new light on how oskar mRNA is trafficked during oogenesis and the RNA features that mediate minus end-directed transport.
Collapse
Affiliation(s)
- Helena Jambor
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Sandra Mueller
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Simon L. Bullock
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Anne Ephrussi
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| |
Collapse
|
47
|
Ahuja A, Extavour CG. Patterns of molecular evolution of the germ line specification gene oskar suggest that a novel domain may contribute to functional divergence in Drosophila. Dev Genes Evol 2014; 224:65-77. [DOI: 10.1007/s00427-013-0463-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Accepted: 12/07/2013] [Indexed: 01/04/2023]
|
48
|
Tsai YC, Chiang W, Liou W, Lee WH, Chang YW, Wang PY, Li YC, Tanaka T, Nakamura A, Pai LM. Endophilin B is required for the Drosophila oocyte to endocytose yolk downstream of Oskar. Development 2014; 141:563-73. [PMID: 24401369 DOI: 10.1242/dev.097022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The nutritional environment is crucial for Drosophila oogenesis in terms of controlling hormonal conditions that regulate yolk production and the progress of vitellogenesis. Here, we discovered that Drosophila Endophilin B (D-EndoB), a member of the endophilin family, is required for yolk endocytosis as it regulates membrane dynamics in developing egg chambers. Loss of D-EndoB leads to yolk content reduction, similar to that seen in yolkless mutants, and also causes poor fecundity. In addition, mutant egg chambers exhibit an arrest at the previtellogenic stage. D-EndoB displayed a crescent localization at the oocyte posterior pole in an Oskar-dependent manner; however, it did not contribute to pole plasm assembly. D-EndoB was found to partially colocalize with Long Oskar and Yolkless at the endocytic membranes in ultrastructure analysis. Using an FM4-64 dye incorporation assay, D-EndoB was also found to promote endocytosis in the oocyte. When expressing the full-length D-endoB(FL) or D-endoB(ΔSH3) mutant transgenes in oocytes, the blockage of vitellogenesis and the defect in fecundity in D-endoB mutants was restored. By contrast, a truncated N-BAR domain of the D-EndoB only partially rescued these defects. Taken together, these results allow us to conclude that D-EndoB contributes to the endocytic activity downstream of Oskar by facilitating membrane dynamics through its N-BAR domain in the yolk uptake process, thereby leading to normal progression of vitellogenesis.
Collapse
Affiliation(s)
- Yi-Cheng Tsai
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, 333, Taiwan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
49
|
Optimized RNA ISH, RNA FISH and protein-RNA double labeling (IF/FISH) in Drosophila ovaries. Nat Protoc 2013; 8:2158-79. [PMID: 24113787 DOI: 10.1038/nprot.2013.136] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In situ hybridization (ISH) is a powerful technique for detecting nucleic acids in cells and tissues. Here we describe three ISH procedures that are optimized for Drosophila ovaries: whole-mount, digoxigenin-labeled RNA ISH; RNA fluorescent ISH (FISH); and protein immunofluorescence (IF)-RNA FISH double labeling (IF/FISH). Each procedure balances conflicting requirements for permeabilization, fixation and preservation of antigenicity to detect RNA and protein expression with high resolution and sensitivity. The ISH protocol uses alkaline phosphatase-conjugated digoxigenin antibodies followed by a color reaction, whereas FISH detection involves tyramide signal amplification (TSA). To simultaneously preserve antigens for protein detection and enable RNA probe penetration for IF/FISH, we perform IF before FISH and use xylenes and detergents to permeabilize the tissue rather than proteinase K, which can damage the antigens. ISH and FISH take 3 d to perform, whereas IF/FISH takes 5 d. Probe generation takes 1 or 2 d to perform.
Collapse
|
50
|
Drosophila oocyte polarity and cytoskeleton organization require regulation of Ik2 activity by Spn-F and Javelin-like. Mol Cell Biol 2013; 33:4371-80. [PMID: 24019068 DOI: 10.1128/mcb.00713-13] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The Drosophila melanogaster Spn-F, Ik2, and Javelin-like (Jvl) proteins interact to regulate oocyte mRNA localization and cytoskeleton organization. However, the mechanism by which these proteins interact remains unclear. Using antibodies to activated Ik2, we showed that this protein is found at the region of oocyte and follicle cell where microtubule minus ends are enriched. We demonstrate that germ line Ik2 activation is diminished both in jvl and in spn-F mutant ovaries. Structure-function analysis of Spn-F revealed that the C-terminal end is critical for protein function, since it alone was able to rescue spn-F sterility. On the other hand, germ line expression of Spn-F lacking its conserved C-terminal region (Spn-FΔC) phenocopied ik2, leading to production of ventralized eggshell and bicaudal embryos. In Spn-FΔC-expressing oocytes, Gurken protein is mislocalized and oskar mRNA and protein localization is disrupted. Expression of Ik2 rescued Spn-FΔC ovarian phenotypes. We found that whereas Spn-F physically interacts with Ik2 and Jvl, Spn-FΔC physically interacts with Ik2 but not with Jvl. Thus, expression of Spn-FΔC, which lacks the Jvl-interacting domain, probably interferes with interaction of Ik2 and Jvl. In summary, our results demonstrate that Spn-F mediates the interaction between Ik2 and Jvl to control Ik2 activity.
Collapse
|