The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Florence L Marlow - One of the best experts on this subject based on the ideXlab platform.
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Visualizing the Balbiani Body in Zebrafish Oocytes.
Methods in molecular biology (Clifton N.J.), 2019Co-Authors: Kathyann Lee, Florence L MarlowAbstract:Approaches to visualize the Balbiani Body of zebrafish primary oocytes using protein, RNA, and mitochondrial markers are described. The method involves isolation, histology, staining, and microscopic examination of early zebrafish oocytes. These techniques can be applied to visualize gene products that are localized to the Balbiani Body, and when applied to mutants can be used to decipher molecular and genetic pathways acting in Balbiani Body development in early oocytes.
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Correction: rbpms2 functions in Balbiani Body architecture and ovary fate.
PLoS genetics, 2018Co-Authors: Odelya H. Kaufman, Sophie Rothhämel, Kathyann Lee, Manon Martin, Florence L MarlowAbstract:[This corrects the article DOI: 10.1371/journal.pgen.1007489.].
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rbpms2 functions in Balbiani Body architecture and ovary fate.
PLoS genetics, 2018Co-Authors: Odelya H. Kaufman, Sophie Rothhämel, Kathyann Lee, Manon Martin, Florence L MarlowAbstract:The most prominent developmental regulators in oocytes are RNA-binding proteins (RNAbps) that assemble their targets into ribonucleoprotein granules where they are stored, transported and translationally regulated. RNA-binding protein of multiple splice forms 2, or Rbpms2, interacts with molecules that are essential to reproduction and egg patterning, including bucky ball, a key factor for Bb formation. Rbpms2 is localized to germ granules in primordial germ cells (PGCs) and to the Balbiani Body (Bb) of oocytes, although the mechanisms regulating Rbpms2 localization to these structures are unknown. Using mutant Rbpms2 proteins, we show that Rbpms2 requires distinct protein domains to localize within germ cells and somatic cells. Accumulation and localization to subcellular compartments in the germline requires an intact RNA binding domain. Whereas in zebrafish somatic blastula cells, the conserved C-terminal domain promotes localization to the bipolar centrosomes/spindle. To investigate Rbpms2 functions, we mutated the duplicated and functionally redundant zebrafish rbpms2 genes. The gonads of rbpms2a;2b (rbpms2) mutants initially contain early oocytes, however definitive oogenesis ultimately fails during sexual differentiation and, rbpms2 mutants develop as fertile males. Unlike other genes that promote oogenesis, failure to maintain oocytes in rbpms2 mutants was not suppressed by mutation of Tp53. These findings reveal a novel and essential role for rbpms2 in oogenesis. Ultrastructural and immunohistochemical analyses revealed that rbpms2 is not required for the asymmetric accumulation of mitochondria and Buc protein in oocytes, however its absence resulted in formation of abnormal Buc aggregates and atypical electron-dense cytoplasmic inclusions. Our findings reveal novel and essential roles for rbpms2 in Buc organization and oocyte differentiation.
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Summary and model depicting Rbpms2 localizing domains, and consequences of rbpms2 loss on Buc and Balbiani Body architecture.
2018Co-Authors: Odelya H. Kaufman, Sophie Rothhämel, Kathyann Lee, Manon Martin, Florence L MarlowAbstract:(A) Chart depicting wild-type and mutant Rbpms2 proteins and the contribution of Rbpms2 functional domains to protein localization within subcellular aggregates of somatic and germline cell types. Y = yes, N = no, P = partial, ND = not determined. (B) In 293 (somatic) cells Rbpms2 (green) requires its C-terminus, but not the RNA binding domain for somatic cell granule localization; whereas, in somatic cells of the zebrafish blastula Rbpms2 accumulates in P-bodies (yellow and red dots) and Dcp2 negative granules (green dots) but not Tial-1 positive stress granules and requires an intact RNA binding domain. Similarly, in germline cells (PGCs and oocytes) the RNA binding domain, and presumably RNA binding is required for localization to germ granules and the Balbiani Body, and the C-terminus contributes to the wild-type localization of the proteins. (C) Rbpms2 in wild-type primary oocytes promotes Balbiani Body assembly or cohesiveness possibly through interaction with Bucky ball protein via the Rbpms2 C-terminus or via interaction with buc RNA. (D) In rbpms2 double mutants, mitochondria are asymmetrically present within early oocytes and associate with nuage. Although Bucky ball protein is translated, no cohesive Buc structure forms in the Bb. Instead the Bucky ball domain is scattered and donut shaped, and large atypical electron dense bodies form in the cytoplasm, reflecting either failure to assemble the Balbiani Body or its premature disassembly.
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Acquisition of Oocyte Polarity.
Results and problems in cell differentiation, 2017Co-Authors: Mara Clapp, Florence L MarlowAbstract:Acquisition of oocyte polarity involves complex translocation and aggregation of intracellular organelles, RNAs, and proteins, along with strict posttranscriptional regulation. While much is still unknown regarding the formation of the animal-vegetal axis, an early marker of polarity, animal models have contributed to our understanding of these early processes controlling normal oogenesis and embryo development. In recent years, it has become clear that proteins with self-assembling properties are involved in assembling discrete subcellular compartments or domains underlying subcellular asymmetries in the early mitotic and meiotic cells of the female germline. These include asymmetries in duplication of the centrioles and formation of centrosomes and assembly of the organelle and RNA-rich Balbiani Body, which plays a critical role in oocyte polarity. Notably, at specific stages of germline development, these transient structures in oocytes are temporally coincident and align with asymmetries in the position and arrangement of nuclear components, such as the nuclear pore and the chromosomal bouquet and the centrioles and cytoskeleton in the cytoplasm. Formation of these critical, transient structures and arrangements involves microtubule pathways, intrinsically disordered proteins (proteins with domains that tend to be fluid or lack a rigid ordered three-dimensional structure ranging from random coils, globular domains, to completely unstructured proteins), and translational repressors and activators. This review aims to examine recent literature and key players in oocyte polarity.
Szczepan M. Bilinski - One of the best experts on this subject based on the ideXlab platform.
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Morphogenesis of the Balbiani Body in developing oocytes of an orthopteran, Metrioptera brachyptera, and multiplication of female germline mitochondria.
Journal of morphology, 2020Co-Authors: Malgorzata Sekula, Waclaw Tworzydlo, Szczepan M. BilinskiAbstract:Balbiani Body (Bb) is a female germline specific organelle complex. Although the morphology and morphogenesis of the Bb have been analyzed in numerous vertebrate and invertebrate species, the role and ultimate fate of this organelle assemblage are still under debate. As a result, various functions have been attributed to the Bb in given animal lineages or even species. Our analyses showed that in the bush cricket, Metrioptera brachyptera, the Bb is an elaborate and highly dynamic structure positioned at one side of the oocyte nucleus. It forms in early previtellogenic oocytes and consists of two compartments: perinuclear and cytoplasmic. In the cytoplasmic compartment, characteristic complexes of nuage and polymorphous mitochondria are present. Computer-aided 3D reconstructions revealed that mitochondria clustered around neighboring nuage accumulations remain in a physical contact and form an extensive, though dispersed network. As oogenesis progresses, nuage/mitochondria complexes are partitioned into progressively smaller entities that become separated from each other. Concurrently, the mitochondrial network splits into small individual mitochondria populating the whole ooplasm. Immunohistochemical analysis showed that the latter process involves dynamin-related protein 1 (Drp1). Collectively, our findings suggest that in basal insect species, the Bb might be responsible for the selection as well as multiplication of the oocyte mitochondria.
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Transmission of Functional, Wild-Type Mitochondria and the Fittest mtDNA to the Next Generation: Bottleneck Phenomenon, Balbiani Body, and Mitophagy
Genes, 2020Co-Authors: Waclaw Tworzydlo, Malgorzata Sekula, Szczepan M. BilinskiAbstract:The most important role of mitochondria is to supply cells with metabolic energy in the form of adenosine triphosphate (ATP). As synthesis of ATP molecules is accompanied by the generation of reactive oxygen species (ROS), mitochondrial DNA (mtDNA) is highly vulnerable to impairment and, consequently, accumulation of deleterious mutations. In most animals, mitochondria are transmitted to the next generation maternally, i.e., exclusively from female germline cells (oocytes and eggs). It has been suggested, in this context, that a specialized mechanism must operate in the developing oocytes enabling escape from the impairment and subsequent transmission of accurate (devoid of mutations) mtDNA from one generation to the next. Literature survey suggest that two distinct and irreplaceable pathways of mitochondria transmission may be operational in various animal lineages. In some taxa, the mitochondria are apparently selected: functional mitochondria with high inner membrane potential are transferred to the cells of the embryo, whereas those with low membrane potential (overloaded with mutations in mtDNA) are eliminated by mitophagy. In other species, the respiratory activity of germline mitochondria is suppressed and ROS production alleviated leading to the same final effect, i.e., transmission of undamaged mitochondria to offspring, via an entirely different route.
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Organelle assemblages implicated in the transfer of oocyte components to the embryo: an insect perspective.
Current opinion in insect science, 2018Co-Authors: Szczepan M. Bilinski, Mariusz K. Jaglarz, Waclaw TworzydloAbstract:Besides reserve materials (yolk spheres, lipid droplets), ribosomes and various mRNA species, insect oocytes contain large easily morphologically recognizable organelle assemblages: the Balbiani Body and the oosome (pole plasm). These assemblages are implicated in the transfer of oocyte components (mitochondria, polar granules) to the embryo that is to offspring. Here, we review present knowledge of morphology, morphogenesis, molecular composition and function/s of these assemblages. We discuss also the morphogenesis and presumed function of unconventional organelle assemblages, dormant stacks of endoplasmic reticulum, recently described in the oocytes and early embryos of a viviparous dermapteran, Hemimerus talpoides.
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Selection of mitochondria in female germline cells: is Balbiani Body implicated in this process?
Journal of Assisted Reproduction and Genetics, 2017Co-Authors: Szczepan M. Bilinski, Malgorzata Kloc, Waclaw TworzydloAbstract:Early oocytes of nearly all animal species contain a transient organelle assemblage termed the Balbiani Body. Structure and composition of this assemblage may vary even between closely related species. Despite this variability, the Balbiani Body always comprises of numerous tightly clustered mitochondria and accumulations of nuage material. It has been suggested that the Balbiani Body is an evolutionarily ancestral structure, which plays a role in various processes such as the localization of organelles and macromolecules to the germ plasm, lipidogenesis, as well as the selection/elimination of dysfunctional mitochondria from female germline cells. We suggest that the selection/elimination of mitochondria is a primary and evolutionarily ancestral function of Balbiani Body, and that the other functions are secondary, evolutionarily derived additions. We propose a simple model explaining the role of the Balbiani Body in the selection of mitochondria, i.e., in the mitochondrial DNA (mtDNA) bottleneck phenomenon.
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Meiosis, Balbiani Body and early asymmetry of Thermobia oocyte
Protoplasma, 2017Co-Authors: Waclaw Tworzydlo, Magdalena Marek, Elzbieta Kisiel, Szczepan M. BilinskiAbstract:The meiotic division guarantees maintenance of a genetic diversity; it consists of several stages, with prophase I being the longest and the most complex. We decided to follow the course of initial stages of meiotic division in ovaries of Thermobia domestica using modified techniques of squash preparations, semithin sections, and electron microscopy. We show that germaria contain numerous germline cells that can be classified into three categories: cystoblasts, meiotic oocytes, and growing previtellogenic oocytes. The cystoblasts are located most apically. The meiotic oocytes occupy the middle part of the germarium, and the previtellogenic oocytes can be found in the most basal part, near the vitellarium. Analyses of the semithin sections and squash preparations show that post leptotene meiotic chromosomes gather in one region of the nucleoplasm where they form the so-called bouquet. The telomeres of the bouquet chromosomes are attached to a relatively small area (segment) of the nuclear envelope. Next to this envelope segment, the nucleolar organizers are also located. We show that in concert to sequential changes inside the oocyte nuclei, rearrangement of organelles within the ooplasm (oocyte cytoplasm) takes place. This leads to the formation of the Balbiani Body and consequent asymmetry of the ooplasm. These early nuclear and cytoplasmic asymmetries, however, are transient. During diplotene, the chromosome bouquet disappears, while the Balbiani Body gradually disperses throughout the ooplasm. Finally, our observations indicate the presence of lampbrush chromosomes in the nuclei of previtellogenic oocytes. In the close vicinity to lampbrush chromosomes, characteristic spherical nuclear bodies are present.
Mary C Mullins - One of the best experts on this subject based on the ideXlab platform.
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The vertebrate Balbiani Body, germ plasm, and oocyte polarity.
Current topics in developmental biology, 2019Co-Authors: Allison Jamieson-lucy, Mary C MullinsAbstract:The fate of future generations depends on a high-quality germ line. For a female to successfully produce offspring, her oocytes must be successfully specified and their contents meticulously organized. Germ cells are specified by two general mechanisms: inductive and inherited. In the inductive mechanism, the primordial germ cells (PGCs) are induced by signals from the surrounding cells. In the inherited mechanism, PGCs are specified by passing localized germ plasm material from the oocyte to the future germ cells. The Balbiani Body, a conserved oocyte aggregate, facilitates the organization of the oocyte into a polarized cell with discrete cytoplasmic domains, including localizing the germ plasm. In the mouse, the Balbiani Body is implicated in oocyte survival, while in frogs and zebrafish the Balbiani Body carries specific mRNAs to the vegetal pole. These asymmetric mRNAs form the foundation of the functionally polarized oocyte and play important roles in axial patterning and germ plasm formation of the embryo.
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Isolation of Zebrafish Balbiani Bodies for Proteomic Analysis.
Methods in molecular biology (Clifton N.J.), 2019Co-Authors: Allison Jamieson-lucy, Mary C MullinsAbstract:Proteomic characterization of isolated organelles can provide insight into the functional components of the structure and novel targets for further testing. Germplasm in developing oocytes is difficult to isolate for protein identification because not all types of germplasm are stable outside of the cytoplasm. In zebrafish, the Balbiani Body forms a proteinaceous aggregate that contains the germplasm and we found is stable outside of the oocyte. Here we present a manual isolation protocol that collects intact Balbiani bodies from stage I zebrafish oocytes. We lysed oocytes by passing them through a syringe, and then used a fine injection needle to wick up Balbiani bodies by capillary action with minimal buffer solution. Using this protocol we collected sufficient material for proteomic analysis of the zebrafish Balbiani Body.
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microtubule actin crosslinking factor 1 macf1 domain function in Balbiani Body dissociation and nuclear positioning
PLOS Genetics, 2017Co-Authors: Matias Escobaraguirre, Allison Jamiesonlucy, Hong Zhang, Mary C MullinsAbstract:Animal-vegetal (AV) polarity of most vertebrate eggs is established during early oogenesis through the formation and disassembly of the Balbiani Body (Bb). The Bb is a structure conserved from insects to humans that appears as a large granule, similar to a mRNP granule composed of mRNA and proteins, that in addition contains mitochondria, ER and Golgi. The components of the Bb, which have amyloid-like properties, include germ cell and axis determinants of the embryo that are anchored to the vegetal cortex upon Bb disassembly. Our lab discovered in zebrafish the only gene known to function in Bb disassembly, microtubule-actin crosslinking factor 1a (macf1a). Macf1 is a conserved, giant multi-domain cytoskeletal linker protein that can interact with microtubules (MTs), actin filaments (AF), and intermediate filaments (IF). In macf1a mutant oocytes the Bb fails to dissociate, the nucleus is acentric, and AV polarity of the oocyte and egg fails to form. The cytoskeleton-dependent mechanism by which Macf1a regulates Bb mRNP granule dissociation was unknown. We found that disruption of AFs phenocopies the macf1a mutant phenotype, while MT disruption does not. We determined that cytokeratins (CK), a type of IF, are enriched in the Bb. We found that Macf1a localizes to the Bb, indicating a direct function in regulating its dissociation. We thus tested if Macf1a functions via its actin binding domain (ABD) and plectin repeat domain (PRD) to integrate cortical actin and Bb CK, respectively, to mediate Bb dissociation at the oocyte cortex. We developed a CRISPR/Cas9 approach to delete the exons encoding these domains from the macf1a endogenous locus, while maintaining the open reading frame. Our analysis shows that Macf1a functions via its ABD to mediate Bb granule dissociation and nuclear positioning, while the PRD is dispensable. We propose that Macf1a does not function via its canonical mechanism of linking two cytoskeletal systems together in dissociating the Bb. Instead our results suggest that Macf1a functions by linking one cytoskeletal system, cortical actin, to another structure, the Bb, where Macf1a is localized. Through this novel linking process, it dissociates the Bb at the oocyte cortex, thus specifying the AV axis of the oocyte and future egg. To our knowledge, this is also the first study to use genome editing to unravel the module-dependent function of a cytoskeletal linker.
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Coordination of cellular differentiation, polarity, mitosis and meiosis – New findings from early vertebrate oogenesis
Developmental biology, 2017Co-Authors: Yaniv M Elkouby, Mary C MullinsAbstract:A mechanistic dissection of early oocyte differentiation in vertebrates is key to advancing our knowledge of germline development, reproductive biology, the regulation of meiosis, and all of their associated disorders. Recent advances in the field include breakthroughs in the identification of germline stem cells in Medaka, in the cellular architecture of the germline cyst in mice, in a mechanistic dissection of chromosomal pairing and bouquet formation in meiosis in mice, in tracing oocyte symmetry breaking to the chromosomal bouquet of meiosis in zebrafish, and in the biology of the Balbiani Body, a universal oocyte granule. Many of the major events in early oogenesis are universally conserved, and some are co-opted for species-specific needs. The chromosomal events of meiosis are of tremendous consequence to gamete formation and have been extensively studied. New light is now being shed on other aspects of early oocyte differentiation, which were traditionally considered outside the scope of meiosis, and their coordination with meiotic events. The emerging theme is of meiosis as a common groundwork for coordinating multifaceted processes of oocyte differentiation. In an accompanying manuscript we describe methods that allowed for investigations in the zebrafish ovary to contribute to these breakthroughs. Here, we review these advances mostly from the zebrafish and mouse. We discuss oogenesis concepts across established model organisms, and construct an inclusive paradigm for early oocyte differentiation in vertebrates.
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Methods for the analysis of early oogenesis in Zebrafish.
Developmental biology, 2016Co-Authors: Yaniv M Elkouby, Mary C MullinsAbstract:Oocyte differentiation is a highly dynamic and intricate developmental process whose mechanistic understanding advances female reproduction, fertility, and ovarian cancer biology. Despite the many attributes of the zebrafish model, it has yet to be fully exploited for the investigation of early oocyte differentiation and ovarian development. This is partly because the properties of the adult zebrafish ovary make it technically challenging to access early stage oocytes. As a result, characterization of these stages has been lacking and tools for their analysis have been insufficient. To overcome these technical hurdles, we took advantage of the juvenile zebrafish ovary, where early stage oocytes can readily be found in high numbers and progress in a predictable manner. We characterized the earliest stages of oocyte differentiation and ovarian development and defined accurate staging criteria. We further developed protocols for quantitative microscopy, live time-lapse imaging, ovarian culture, and isolation of stage-specific oocytes for biochemical analysis. These methods have recently provided us with an unprecedented view of early oogenesis, allowing us to study formation of the Balbiani Body, a universal oocyte granule that is associated with oocyte survival in mice and required for oocyte and egg polarity in fish and frogs. Despite its tremendous developmental significance, the Bb has been little investigated and how it forms was unknown in any species for over two centuries. We were able to trace Balbiani Body formation and oocyte symmetry breaking to the onset of meiosis. Through this investigation we revealed novel cytoskeletal structures in oocytes and the contribution of specialized cellular organization to differentiation. Overall, the juvenile zebrafish ovary arises as an exciting model for studies of cell and developmental biology. We review these and other recent advances in vertebrate oogenesis in an accompanying manuscript in this issue of Developmental Biology. Here, we describe the protocols for ovarian investigation that we developed in the zebrafish, including all experimental steps that will easily allow others to reproduce such analysis. This juvenile ovary toolbox also contributes to establishing the zebrafish as a model for post-larval developmental stages.
Malgorzata Kloc - One of the best experts on this subject based on the ideXlab platform.
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Selection of mitochondria in female germline cells: is Balbiani Body implicated in this process?
Journal of Assisted Reproduction and Genetics, 2017Co-Authors: Szczepan M. Bilinski, Malgorzata Kloc, Waclaw TworzydloAbstract:Early oocytes of nearly all animal species contain a transient organelle assemblage termed the Balbiani Body. Structure and composition of this assemblage may vary even between closely related species. Despite this variability, the Balbiani Body always comprises of numerous tightly clustered mitochondria and accumulations of nuage material. It has been suggested that the Balbiani Body is an evolutionarily ancestral structure, which plays a role in various processes such as the localization of organelles and macromolecules to the germ plasm, lipidogenesis, as well as the selection/elimination of dysfunctional mitochondria from female germline cells. We suggest that the selection/elimination of mitochondria is a primary and evolutionarily ancestral function of Balbiani Body, and that the other functions are secondary, evolutionarily derived additions. We propose a simple model explaining the role of the Balbiani Body in the selection of mitochondria, i.e., in the mitochondrial DNA (mtDNA) bottleneck phenomenon.
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Hermes (Rbpms) is a Critical Component of RNP Complexes that Sequester Germline RNAs during Oogenesis
Journal of Developmental Biology, 2016Co-Authors: Tristan Aguero, Malgorzata Kloc, Mary Lou King, Yi Zhou, Patrick Chang, Evelyn Houliston, Mary KingAbstract:The germ cell lineage in Xenopus is specified by the inheritance of germ plasm that assembles within the mitochondrial cloud or Balbiani Body in stage I oocytes. Specific RNAs, such as nanos1, localize to the germ plasm. nanos1 has the essential germline function of blocking somatic gene expression and thus preventing Primordial Germ Cell (PGC) loss and sterility. Hermes/Rbpms protein and nanos RNA co-localize within germinal granules, diagnostic electron dense particles found within the germ plasm. Previous work indicates that nanos accumulates within the germ plasm through a diffusion/entrapment mechanism. Here we show that Hermes/Rbpms interacts with nanos through sequence specific RNA localization signals found in the nanos-3'UTR. Importantly, Hermes/Rbpms specifically binds nanos, but not Vg1 RNA in the nucleus of stage I oocytes. In vitro binding data show that Hermes/Rbpms requires additional factors that are present in stage I oocytes in order to bind nanos1. One such factor may be hnRNP I, identified in a yeast-2-hybrid screen as directly interacting with Hermes/Rbpms. We suggest that Hermes/Rbpms functions as part of a RNP complex in the nucleus that facilitates selection of germline RNAs for germ plasm localization. We propose that Hermes/Rbpms is required for nanos RNA to form within the germinal granules and in this way, participates in the germline specific translational repression and sequestration of nanos RNA.
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Balbiani Body nuage and sponge bodies the germ plasm pathway players
Arthropod Structure & Development, 2014Co-Authors: Malgorzata Kloc, Waclaw Tworzydlo, Izabela Jedrzejowska, Szczepan M. BilinskiAbstract:In many animal species, germ cells are specified by maternally provided, often asymmetrically localized germ cell determinant, termed the germ plasm. It has been shown that in model organisms such as Xenopus laevis, Danio rerio and Drosophila melanogaster germ plasm components (various proteins, mRNAs and mitochondria) are delivered to the proper position within the egg cell by germline specific organelles, i.e. Balbiani bodies, nuage accumulations and/or sponge bodies. In the present article, we review the current knowledge on morphology, molecular composition and functioning of these organelles in main lineages of arthropods and different ovary types on the backdrop of data derived from the studies of the model vertebrate species.
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Balbiani Body, nuage and sponge bodies – The germ plasm pathway players
Arthropod structure & development, 2014Co-Authors: Malgorzata Kloc, Waclaw Tworzydlo, Izabela Jędrzejowska, Szczepan M. BilinskiAbstract:In many animal species, germ cells are specified by maternally provided, often asymmetrically localized germ cell determinant, termed the germ plasm. It has been shown that in model organisms such as Xenopus laevis, Danio rerio and Drosophila melanogaster germ plasm components (various proteins, mRNAs and mitochondria) are delivered to the proper position within the egg cell by germline specific organelles, i.e. Balbiani bodies, nuage accumulations and/or sponge bodies. In the present article, we review the current knowledge on morphology, molecular composition and functioning of these organelles in main lineages of arthropods and different ovary types on the backdrop of data derived from the studies of the model vertebrate species.
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the Balbiani Body in the female germline cells of an earwig opisthocosmia silvestris
Zoological Science, 2009Co-Authors: Waclaw Tworzydlo, Malgorzata Kloc, Szczepan M. BilinskiAbstract:In the majority of invertebrate and vertebrate species, gametogenesis starts with the formation of cysts (clusters) of sibling germline cells. Cysts originate as the result of mitotic divisions of a specialized germline cell, the cystoblast. Since these divisions are incomplete, the cyst cells (cystocytes) remain connected by stable connections, termed intercellular bridges (ring canals). In forficuloid earwigs, female germ cell cysts are composed of two cells only: the pro-oocte and pronurse cells. We show that in Opisthocosmia silvestris, the cystoblast, as well as both cells of the cyst, contain the Balbiani Body (Bb), a distinct cytoplasmic organelle composed of numerous mitochondria. We also show that in the cyst cells, the Bbs are invariably located next to the fusome, a specialized cytoplasm occupying the bridge connecting sibling cells.
Waclaw Tworzydlo - One of the best experts on this subject based on the ideXlab platform.
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Morphogenesis of the Balbiani Body in developing oocytes of an orthopteran, Metrioptera brachyptera, and multiplication of female germline mitochondria.
Journal of morphology, 2020Co-Authors: Malgorzata Sekula, Waclaw Tworzydlo, Szczepan M. BilinskiAbstract:Balbiani Body (Bb) is a female germline specific organelle complex. Although the morphology and morphogenesis of the Bb have been analyzed in numerous vertebrate and invertebrate species, the role and ultimate fate of this organelle assemblage are still under debate. As a result, various functions have been attributed to the Bb in given animal lineages or even species. Our analyses showed that in the bush cricket, Metrioptera brachyptera, the Bb is an elaborate and highly dynamic structure positioned at one side of the oocyte nucleus. It forms in early previtellogenic oocytes and consists of two compartments: perinuclear and cytoplasmic. In the cytoplasmic compartment, characteristic complexes of nuage and polymorphous mitochondria are present. Computer-aided 3D reconstructions revealed that mitochondria clustered around neighboring nuage accumulations remain in a physical contact and form an extensive, though dispersed network. As oogenesis progresses, nuage/mitochondria complexes are partitioned into progressively smaller entities that become separated from each other. Concurrently, the mitochondrial network splits into small individual mitochondria populating the whole ooplasm. Immunohistochemical analysis showed that the latter process involves dynamin-related protein 1 (Drp1). Collectively, our findings suggest that in basal insect species, the Bb might be responsible for the selection as well as multiplication of the oocyte mitochondria.
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Transmission of Functional, Wild-Type Mitochondria and the Fittest mtDNA to the Next Generation: Bottleneck Phenomenon, Balbiani Body, and Mitophagy
Genes, 2020Co-Authors: Waclaw Tworzydlo, Malgorzata Sekula, Szczepan M. BilinskiAbstract:The most important role of mitochondria is to supply cells with metabolic energy in the form of adenosine triphosphate (ATP). As synthesis of ATP molecules is accompanied by the generation of reactive oxygen species (ROS), mitochondrial DNA (mtDNA) is highly vulnerable to impairment and, consequently, accumulation of deleterious mutations. In most animals, mitochondria are transmitted to the next generation maternally, i.e., exclusively from female germline cells (oocytes and eggs). It has been suggested, in this context, that a specialized mechanism must operate in the developing oocytes enabling escape from the impairment and subsequent transmission of accurate (devoid of mutations) mtDNA from one generation to the next. Literature survey suggest that two distinct and irreplaceable pathways of mitochondria transmission may be operational in various animal lineages. In some taxa, the mitochondria are apparently selected: functional mitochondria with high inner membrane potential are transferred to the cells of the embryo, whereas those with low membrane potential (overloaded with mutations in mtDNA) are eliminated by mitophagy. In other species, the respiratory activity of germline mitochondria is suppressed and ROS production alleviated leading to the same final effect, i.e., transmission of undamaged mitochondria to offspring, via an entirely different route.
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Organelle assemblages implicated in the transfer of oocyte components to the embryo: an insect perspective.
Current opinion in insect science, 2018Co-Authors: Szczepan M. Bilinski, Mariusz K. Jaglarz, Waclaw TworzydloAbstract:Besides reserve materials (yolk spheres, lipid droplets), ribosomes and various mRNA species, insect oocytes contain large easily morphologically recognizable organelle assemblages: the Balbiani Body and the oosome (pole plasm). These assemblages are implicated in the transfer of oocyte components (mitochondria, polar granules) to the embryo that is to offspring. Here, we review present knowledge of morphology, morphogenesis, molecular composition and function/s of these assemblages. We discuss also the morphogenesis and presumed function of unconventional organelle assemblages, dormant stacks of endoplasmic reticulum, recently described in the oocytes and early embryos of a viviparous dermapteran, Hemimerus talpoides.
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Selection of mitochondria in female germline cells: is Balbiani Body implicated in this process?
Journal of Assisted Reproduction and Genetics, 2017Co-Authors: Szczepan M. Bilinski, Malgorzata Kloc, Waclaw TworzydloAbstract:Early oocytes of nearly all animal species contain a transient organelle assemblage termed the Balbiani Body. Structure and composition of this assemblage may vary even between closely related species. Despite this variability, the Balbiani Body always comprises of numerous tightly clustered mitochondria and accumulations of nuage material. It has been suggested that the Balbiani Body is an evolutionarily ancestral structure, which plays a role in various processes such as the localization of organelles and macromolecules to the germ plasm, lipidogenesis, as well as the selection/elimination of dysfunctional mitochondria from female germline cells. We suggest that the selection/elimination of mitochondria is a primary and evolutionarily ancestral function of Balbiani Body, and that the other functions are secondary, evolutionarily derived additions. We propose a simple model explaining the role of the Balbiani Body in the selection of mitochondria, i.e., in the mitochondrial DNA (mtDNA) bottleneck phenomenon.
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Meiosis, Balbiani Body and early asymmetry of Thermobia oocyte
Protoplasma, 2017Co-Authors: Waclaw Tworzydlo, Magdalena Marek, Elzbieta Kisiel, Szczepan M. BilinskiAbstract:The meiotic division guarantees maintenance of a genetic diversity; it consists of several stages, with prophase I being the longest and the most complex. We decided to follow the course of initial stages of meiotic division in ovaries of Thermobia domestica using modified techniques of squash preparations, semithin sections, and electron microscopy. We show that germaria contain numerous germline cells that can be classified into three categories: cystoblasts, meiotic oocytes, and growing previtellogenic oocytes. The cystoblasts are located most apically. The meiotic oocytes occupy the middle part of the germarium, and the previtellogenic oocytes can be found in the most basal part, near the vitellarium. Analyses of the semithin sections and squash preparations show that post leptotene meiotic chromosomes gather in one region of the nucleoplasm where they form the so-called bouquet. The telomeres of the bouquet chromosomes are attached to a relatively small area (segment) of the nuclear envelope. Next to this envelope segment, the nucleolar organizers are also located. We show that in concert to sequential changes inside the oocyte nuclei, rearrangement of organelles within the ooplasm (oocyte cytoplasm) takes place. This leads to the formation of the Balbiani Body and consequent asymmetry of the ooplasm. These early nuclear and cytoplasmic asymmetries, however, are transient. During diplotene, the chromosome bouquet disappears, while the Balbiani Body gradually disperses throughout the ooplasm. Finally, our observations indicate the presence of lampbrush chromosomes in the nuclei of previtellogenic oocytes. In the close vicinity to lampbrush chromosomes, characteristic spherical nuclear bodies are present.
