Morphology of Mitochondria in Syncytial Annelid Female Germ-Line Cyst Visualized by Serial Block-Face SEM

Mitochondria change their morphology and distribution depending on the metabolism and functional state of a cell. Here, we analyzed the mitochondria and selected structures in female germ-line cysts in a representative of clitellate annelids – the white worm Enchytraeus albidus in which each germ cell has one cytoplasmic bridge that connects it to a common cytoplasmic mass. Using serial block-face scanning electron microscopy (SBEM), we prepared three-dimensional ultrastructural reconstructions of the entire selected compartments of a cyst at the advanced stage of oogenesis, i.e. the nurse cell, cytophore, and cytoplasmic bridges of all 16 cells (15 nurse cells and oocyte). We revealed extensive mitochondrial networks in the nurse cells, cytophore and mitochondria that pass through the cytoplasmic bridges, which indicates that a mitochondrial network can extend throughout the entire cyst. The dynamic hyperfusion state was suggested for such mitochondrial aggregations. We measured the mitochondria distribution and revealed their polarized distribution in the nurse cells and more abundant accumulation within the cytophore compared to the nurse cell. A close association of mitochondrial networks with dispersed nuage material, which seems to be the structural equivalent of a Balbiani body, not described in clitellate annelids so far, was also revealed.

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Reorganization of the cytoskeleton during Drosophila oogenesis: implications for axis specification and intercellular transport

Development ◽

10.1242/dev.115.4.923 ◽

1992 ◽

Vol 115 (4) ◽

pp. 923-936 ◽

Cited By ~ 72

Author(s):

W.E. Theurkauf ◽

S. Smiley ◽

M.L. Wong ◽

B.M. Alberts

Keyword(s):

Laser Scanning ◽

Laser Scanning Confocal Microscopy ◽

Nurse Cells ◽

Intercellular Transport ◽

Drosophila Oogenesis ◽

Actin Organization ◽

Scanning Confocal Microscopy ◽

Cytoplasmic Bridges ◽

Fluorescence Cytochemistry ◽

Pass Through

Inhibitor studies have implicated microtubules in at least three important developmental processes during Drosophila oogenesis: oocyte determination and growth during stages 1 through 6, positioning of the anterior determinant bicoid mRNA during stages 9 through 12, and ooplasmic streaming during stages 10b through 12. We have used fluorescence cytochemistry together with laser scanning confocal microscopy to identify distinct microtubule structures at each of the above three periods that are likely to be involved in these processes. During stages 1 through 7, maternal components synthesized in nurse cells are transported through cytoplasmic bridges to the oocyte. At this time, microtubules that appear to originate in the oocyte pass through these cytoplasmic bridges into the adjacent nurse cells; these microtubules are likely to serve as a polarized scaffold on which maternal RNAs and proteins are transported. During stages 7 and 8, microtubules in the oocyte cortex reorganize to form an anterior-to-posterior gradient, suggesting a role for microtubules in the localization of morphogenetic determinants. Finally, when ooplasmic streaming begins during stage 10 b, it is accompanied by the assembly of subsurface microtubule arrays that spiral around the oocyte; these arrays disassemble as the oocyte matures and streaming stops. During ooplasmic streaming, many vesicles are closely associated with the subsurface microtubules, suggesting that streaming is driven by vesicle translocation along microtubules. We believe that actin plays a secondary role in each of these morphogenetic events, based on our parallel studies of actin organization during each of the above stages of oogenesis.

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Vps13 is required for timely removal of nurse cell corpses

Development ◽

10.1242/dev.191759 ◽

2020 ◽

Vol 147 (20) ◽

pp. dev191759

Author(s):

Anita I. E. Faber ◽

Marianne van der Zwaag ◽

Hein Schepers ◽

Ellie Eggens-Meijer ◽

Bart Kanon ◽

...

Keyword(s):

Cell Death ◽

Plasma Membrane ◽

Programmed Cell Death ◽

Nurse Cell ◽

Close Association ◽

Follicle Cells ◽

Nurse Cells ◽

Lipid Transfer ◽

Membranous Structure ◽

Membrane Contact Sites

ABSTRACTProgrammed cell death and consecutive removal of cellular remnants is essential for development. During late stages of Drosophila melanogaster oogenesis, the small somatic follicle cells that surround the large nurse cells promote non-apoptotic nurse cell death, subsequently engulf them, and contribute to the timely removal of nurse cell corpses. Here, we identify a role for Vps13 in the timely removal of nurse cell corpses downstream of developmental programmed cell death. Vps13 is an evolutionarily conserved peripheral membrane protein associated with membrane contact sites and lipid transfer. It is expressed in late nurse cells, and persistent nurse cell remnants are observed when Vps13 is depleted from nurse cells but not from follicle cells. Microscopic analysis revealed enrichment of Vps13 in close proximity to the plasma membrane and the endoplasmic reticulum in nurse cells undergoing degradation. Ultrastructural analysis uncovered the presence of an underlying Vps13-dependent membranous structure in close association with the plasma membrane. The newly identified structure and function suggests the presence of a Vps13-dependent process required for complete degradation of bulky remnants of dying cells.

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The Drosophila gene fs(2)cup interacts with otu to define a cytoplasmic pathway required for the structure and function of germ-line chromosomes

Development ◽

10.1242/dev.124.7.1419 ◽

1997 ◽

Vol 124 (7) ◽

pp. 1419-1431 ◽

Cited By ~ 5

Author(s):

L.N. Keyes ◽

A.C. Spradling

Keyword(s):

Nurse Cell ◽

Germ Line ◽

Meiotic Chromosome ◽

Cyst Formation ◽

Nurse Cells ◽

Egg Maturation ◽

Cytoplasmic Proteins ◽

Acid Protein ◽

Membrane Spanning ◽

And Function

The Drosophila ovarian tumor gene (otu) encodes cytoplasmic proteins that are required in germ-line cells for cyst formation, nurse cell chromosome structure and egg maturation. We have analyzed a gene, fs(2)cup, that participates in many of the same processes and interacts with otu genetically. Both nurse cell and oocyte chromosomes require cup to attain a normal morphology. In addition, the gene is needed for the oocyte to grow normally by taking up materials transported from the nurse cells. The gene encodes a 1132-amino-acid protein containing a putative membrane-spanning domain. Cup protein (but not cup RNA) is transported selectively into the oocyte in germarial cysts, like the p104 Otu protein. It is strongly associated with large structures in the cytoplasm and perinuclear region of nurse cells and, like Otu, moves to the periphery of these cells in stages 9–10. Moreover, cup mutations dominantly disrupt meiotic chromosome segregation. We propose that cup, otu and another interacting gene, fs(2)B, take part in a common cytoplasmic pathway with multiple functions during oogenesis.

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Faculty Opinions recommendation of Serial block-face scanning electron microscopy to reconstruct three-dimensional tissue nanostructure.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1022557.793507804 ◽

2015 ◽

Author(s):

Alpha Yap

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Three Dimensional ◽

Face Scanning ◽

Block Face ◽

Scanning Electron

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Mutual Correction of Faulty PCNA Subunits in Temperature-Sensitive Lethal mus209 Mutants of Drosophila melanogaster

Genetics ◽

10.1093/genetics/154.4.1721 ◽

2000 ◽

Vol 154 (4) ◽

pp. 1721-1733

Author(s):

Daryl S Henderson ◽

Ulrich K Wiegand ◽

David G Norman ◽

David M Glover

Keyword(s):

Germ Line ◽

Position Effect ◽

Three Dimensional ◽

Nuclear Antigen ◽

Dimensional Structure ◽

Female Sterility ◽

Temperature Sensitive ◽

Position Effect Variegation ◽

Dna Double Strand Breaks ◽

Mutant Genotype

Abstract Proliferating cell nuclear antigen (PCNA) functions in DNA replication as a processivity factor for polymerases δ and ε, and in multiple DNA repair processes. We describe two temperature-sensitive lethal alleles (mus209B1 and mus2092735) of the Drosophila PCNA gene that, at temperatures permissive for growth, result in hypersensitivity to DNA-damaging agents, suppression of position-effect variegation, and female sterility in which ovaries are underdeveloped and do not produce eggs. We show by mosaic analysis that the sterility of mus209B1 is partly due to a failure of germ-line cells to proliferate. Strikingly, mus209B1 and mus2092735 interact to restore partial fertility to heteroallelic females, revealing additional roles for PCNA in ovarian development, meiotic recombination, and embryogenesis. We further show that, although mus209B1 and mus2092735 homozygotes are each defective in repair of transposase-induced DNA double-strand breaks in somatic cells, this defect is substantially reversed in the heteroallelic mutant genotype. These novel mutations map to adjacent sites on the three-dimensional structure of PCNA, which was unexpected in the context of this observed interallelic complementation. These mutations, as well as four others we describe, reveal new relationships between the structure and function of PCNA.

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pitkinD, a Novel Gain-of-Function Enhancer of Position-Effect Variegation, Affects Chromatin Regulation During Oogenesis and Early Embryogenesis in Drosophila

Genetics ◽

10.1093/genetics/157.3.1227 ◽

2001 ◽

Vol 157 (3) ◽

pp. 1227-1244 ◽

Cited By ~ 1

Author(s):

Steffi Kuhfittig ◽

János Szabad ◽

Gunnar Schotta ◽

Jan Hoffmann ◽

Endre Máthé ◽

...

Keyword(s):

Germ Line ◽

Position Effect ◽

Early Embryogenesis ◽

Position Effect Variegation ◽

Chromatin Regulation ◽

Gain Of Function ◽

Position Effects ◽

Dominant Female ◽

Effect Variegation ◽

Female Germ Line

Abstract The vast majority of the >100 modifier genes of position-effect variegation (PEV) in Drosophila have been identified genetically as haplo-insufficient loci. Here, we describe pitkinDominant (ptnD), a gain-of-function enhancer mutation of PEV. Its exceptionally strong enhancer effect is evident as elevated spreading of heterochromatin-induced gene silencing along euchromatic regions in variegating rearrangements. The ptnD mutation causes ectopic binding of the SU(VAR)3-9 heterochromatin protein at many euchromatic sites and, unlike other modifiers of PEV, it also affects stable position effects. Specifically, it induces silencing of white+ transgenes inserted at a wide variety of euchromatic sites. ptnD is associated with dominant female sterility. +/+ embryos produced by ptnD/+ females mated with wild-type males die at the end of embryogenesis, whereas the ptnD/+ sibling embryos arrest development at cleavage cycle 1-3, due to a combined effect of maternally provided mutant product and an early zygotic lethal effect of ptnD. This is the earliest zygotic effect of a mutation so far reported in Drosophila. Germ-line mosaics show that ptn+ function is required for normal development in the female germ line. These results, together with effects on PEV and white+ transgenes, are consistent with the hypothesis that the ptn gene plays an important role in chromatin regulation during development of the female germ line and in early embryogenesis.

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Dedicated protection for the female germ line

Nature Reviews Genetics ◽

10.1038/nrg2029 ◽

2006 ◽

Vol 8 (1) ◽

pp. 8-8

Author(s):

Magdalena Skipper

Keyword(s):

Germ Line ◽

Female Germ Line

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Numerical Analyses on the Stability of a Deep Coalmine Roadway Passing through a Fault Zone: A Case Study of the Gugui Coalfield in China

Energies ◽

10.3390/en14082114 ◽

2021 ◽

Vol 14 (8) ◽

pp. 2114

Author(s):

Yongshui Kang ◽

Congcong Hou ◽

Jingyi Liu ◽

Zhi Geng ◽

Jianben Chen ◽

...

Keyword(s):

Fault Zone ◽

Distinct Element ◽

Three Dimensional ◽

Tectonic Stress ◽

Three Dimensional Model ◽

Support Strategy ◽

Failure Theory ◽

Calculation Results ◽

Pass Through ◽

The Stability

Massive deformation often occurs when deep coalmine roadways pass through a fault zone due to the poor integrity of rock mass and high tectonic stress. To study deformation characteristics of the surrounding rock in the fault zone of a coalmine, a roadway passing through the FD1041 fault zone in China’s Gugui coalfield was investigated in this research. The geo-stress characteristics of this fault zone were analyzed based on the Mohr failure theory. Furthermore, a three-dimensional model for the experimental roadway in the FD1041 fault zone was built and calculated by a numerical program based on the distinct element method. Stability conditions of the roadway, using several types of support methods, were calculated and compared. Calculation results indicated that pre-grouting provides favorable conditions for the stability of a roadway in a fault zone. Finally, an optimized support strategy was proposed and implemented in the experimental roadway. Monitored results demonstrated that the optimized support strategy is appropriate for this fault zone.

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Evidence against electrophoresis as the principal mode of protein transport in vitellogenic ovarian follicles of Drosophila

Development ◽

10.1242/dev.101.2.279 ◽

1987 ◽

Vol 101 (2) ◽

pp. 279-288

Author(s):

J. Bohrmann ◽

H. Gutzeit

Keyword(s):

Nurse Cell ◽

Protein Transport ◽

Exchange Chromatography ◽

Heterologous Proteins ◽

Nurse Cells ◽

Cell Cytoplasm ◽

Two Dimensional Gel Electrophoresis ◽

Electrophoretic Transport ◽

Indicator Dyes

Charged cell constituents in polytrophic insect follicles are thought to be transported in the nurse cell-oocyte syncytium by way of electrophoresis. This concept, proposed by Woodruff & Telfer (1980) was based on electrophysiological data and microinjection of heterologous proteins using Hyalophora follicles. By microinjecting fluorescently labelled acidic and basic proteins into the nurse cells or oocyte of vitellogenic Drosophila follicles, we failed to obtain evidence for charge-dependent migration of these molecules. We have also analyzed the proteins of nurse cells and oocyte on isoelectric focusing gels, by means of two-dimensional gel electrophoresis, and by ion exchange chromatography to see if basic or acidic proteins accumulate in vivo in nurse cells and oocyte, respectively. For the bulk of the follicular proteins we found no accumulation. Further evidence against an electrophoretic transport system in Drosophila was obtained by estimating the intracellular pH from the colour of indicator dyes microinjected into the follicles; the results indicate that the pH in the nurse cell cytoplasm is lower than that in the ooplasm. According to the model developed for Hyalophora, electrophoretic transport would be favoured by high pH in the nurse cell cytoplasm.

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Multiple products from the shavenbaby-ovo gene region of Drosophila melanogaster: relationship to genetic complexity

Molecular and Cellular Biology ◽

10.1128/mcb.14.10.6809-6818.1994 ◽

1994 ◽

Vol 14 (10) ◽

pp. 6809-6818

Author(s):

M D Garfinkel ◽

J Wang ◽

Y Liang ◽

A P Mahowald

Keyword(s):

Drosophila Melanogaster ◽

Germ Line ◽

Gene Region ◽

Multiple Products ◽

Zinc Finger Motifs ◽

Genetic Complexity ◽

Complex Locus ◽

Female Germ Line ◽

Sensory Structures ◽

Pole Cells

The Drosophila melanogaster shavenbaby (svb)-ovo gene region is a complex locus, containing two distinct but comutable genetic functions. ovo is required for survival and differentiation of female germ line cells and plays a role in germ line sex determination. In contrast, svb is required in both male and female embryos for the production of epidermal locomotor and sensory structures. Sequences required for the two genetic functions are partially overlapping. ovo corresponds to a previously described germ line-dependent 5.0-kb poly(A)+ mRNA that first appears in the germarium and accumulates in nurse cells during oogenesis. The 5.0-kb mRNA is stored in the egg, but it is rapidly lost in the embryos except for its continued presence in the germ line precursor pole cells. The ovo mRNA predicts a 1,028-amino-acid 110.6-kDa protein homologous with transcription factors. We have identified an embryonic mRNA, 7.1 kb in length, that contains exons partially overlapping those of the 5.0-kb poly(A)+ mRNA. The spatial distribution of this newly discovered transcript during midembryogenesis suggests that it corresponds to the svb function. The arrangement of exons common to the 5.0- and 7.1-kb mRNAs suggests that the Ovo and Svb proteins share DNA-binding specificity conferred by four Cys2-His2 zinc finger motifs but differ functionally in their capacity to interact with other components of the transcription machinery.

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