The <i>Drosophila</i> fusome, organelle biogenesis and germ cell differentiation: If you build it…

McKearin, Dennis M.

doi:10.1002/bies.950190209

Cited by 68 publications

(50 citation statements)

References 44 publications

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“…Whether the fusome membranes consist of discrete ERderived vesicles or form a network of interconnected tubules has remained unresolved with evidence for both types of fusome membrane structures observed by electron microscopy (Telfer, 1975;Bü ning, 1994;Lin et al, 1994;McKearin, 1997). It is worth noting that the ER of animal cells is an ideal example of an interconnected membranous compartment and typically exists as a continuous network of branching tubules connected to the nuclear envelope.…”

Section: Ovarian Cysts Share a Common Ermentioning

confidence: 99%

“…Molecular genetic studies over the last ten years indicate the fusome mediates several essential steps in germline cyst development (reviewed in McKearin, 1997). The differentiation of the oocyte depends on the production of a polarized network of microtubules within the cyst, that facilitates the directional transport of specific mRNAs and proteins from the pronurse cells to the single cell that will become the oocyte (Koch and Spitzer, 1983;Theurkauf et al, 1992Theurkauf et al, , 1993.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…The fusome is found in the germline cysts of Drosophila as well as other insects (reviewed in Telfer, 1975;McKearin, 1997). The Drosophila fusome is comprised of cytoplasmic endomembranes, membrane skeletal proteins and polarized microtubules (reviewed in de Cuevas et al, 1997;McKearin, 1997).Molecular genetic studies over the last ten years indicate the fusome mediates several essential steps in germline cyst development (reviewed in McKearin, 1997). The differentiation of the oocyte depends on the production of a polarized network of microtubules within the cyst, that facilitates the directional transport of specific mRNAs and proteins from the pronurse cells to the single cell that will become the oocyte (Koch and Spitzer, 1983;Theurkauf et al, 1992Theurkauf et al, , 1993.…”

mentioning

confidence: 99%

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The Fusome Mediates Intercellular Endoplasmic Reticulum Connectivity inDrosophilaOvarian Cysts

Snapp

Iida

Frescas

et al. 2004

MBoC

107

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Drosophila ovarian cysts arise through a series of four synchronous incomplete mitotic divisions. After each round of mitosis, a membranous organelle, the fusome, grows along the cleavage furrow and the remnants of the mitotic spindle to connect all cystocytes in a cyst. The fusome is essential for the pattern and synchrony of the mitotic cyst divisions as well as oocyte differentiation. Using live cell imaging, greenfluorescent protein-tagged proteins, and photobleaching techniques, we demonstrate that fusomal endomembranes are part of a single continuous endoplasmic reticulum (ER) that is shared by all cystocytes in dividing ovarian cysts. Membrane and lumenal proteins of the common ER freely and rapidly diffuse between cystocytes. The fusomal ER mediates intercellular ER connectivity by linking the cytoplasmic ER membranes of all cystocytes within a cyst. Before entry into meiosis and onset of oocyte differentiation (between region 1 and region 2A), ER continuity between cystocytes is lost. Furthermore, analyses of hts and Dhc64c mutants indicate that intercellular ER continuity within dividing ovarian cysts requires the fusome cytoskeletal component and suggest a possible role for the common ER in synchronizing mitotic cyst divisions. INTRODUCTIONGametogenesis takes place within germline cysts in a wide array of organisms (Telfer, 1975;Bü ning, 1994;de Cuevas et al., 1997). In Drosophila a single oocyte develops within the environment of a 16-cell cyst. The development of this cyst occurs in a series of morphologically defined regions (see Figure 1A). Cyst production begins when a germline stem cell divides asymmetrically to produce a cystoblast. The cystoblast undergoes four synchronous mitotic divisions (regions 1 and 2a), with incomplete cytokinesis, to produce a cluster of 16 cells that are connected via arrested mitotic cleavage furrows (reviewed in de Cuevas et al., 1997). Later in oogenesis, the arrested cleavage furrows mature into stable ring canals and are reinforced with an actin cytoskeleton (reviewed in Mahajan-Miklos and Cooley, 1994). Initially, all 16 cystocytes develop in synchrony. However, as development proceeds, differentiation within the cyst becomes asynchronous. Ultimately, only one cell commits to meiosis and differentiates as the oocyte, whereas the other 15 cystocytes enter the endocycle and develop as trophic nurse cells.A unique membranous organelle, the fusome, grows and branches along the spindle equators after each mitotic division to physically connect all cells within a cyst. The fusome is found in the germline cysts of Drosophila as well as other insects (reviewed in Telfer, 1975;McKearin, 1997). The Drosophila fusome is comprised of cytoplasmic endomembranes, membrane skeletal proteins and polarized microtubules (reviewed in de Cuevas et al., 1997;McKearin, 1997).Molecular genetic studies over the last ten years indicate the fusome mediates several essential steps in germline cyst development (reviewed in McKearin, 1997). The differentiation of the oocyte depends on the pr...

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Section: Ovarian Cysts Share a Common Ermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

The Fusome Mediates Intercellular Endoplasmic Reticulum Connectivity inDrosophilaOvarian Cysts

Snapp

Iida

Frescas

et al. 2004

MBoC

107

View full text Add to dashboard Cite

show abstract

“…However, little is known about how ectopic expression of Bam drives GSC differentiation. In this study, we showed that knockdown of CycA significantly suppressed the GSC-loss phenotype induced by A hallmark of early germ cell development is that each round of cyst division is accompanied by a morphological change of a germ cell-specific organelle called the fusome (32). While it is observed as a spherical dot in GSCs/CBs, the fusome progressively grows upon cell division to become elongated and finally a branched structure in matured cysts.…”

Section: Discussionmentioning

confidence: 78%

Bam-dependent deubiquitinase complex can disrupt germ-line stem cell maintenance by targeting cyclin A

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Drosophila germ-line stem cells (GSCs) provide an excellent model to study the regulatory mechanisms of stem cells in vivo. Bag of marbles (bam) has been demonstrated to be necessary and sufficient to promote GSC and cystoblast differentiation. Despite extensive investigation of its regulation and genetic functions, the biochemical nature of the Bam protein has been unknown. Here, we report that Bam is an ubiquitin-associated protein and controls the turnover of cyclin A (CycA). Mechanistically, we found that Bam associated with Otu to form a deubiquitinase complex that stabilized CycA by deubiquitination, thus providing a mechanism to explain how ectopic expression of Bam in GSCs promotes differentiation. Collectively, our findings not only identify a biochemical function of Bam, which contributes to GSC fate determination, but also emphasizes the critical role of proper expression of cyclin proteins mediated by both ubiquitination and deubiquitination pathways in balancing stem cell self-renewal and differentiation.

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Drosophila variable nurse cells encodes arrest defective 1 (ARD1), the catalytic subunit of the major N‐terminal acetyltransferase complex

Wang

Mijares

Gall

et al. 2010

Developmental Dynamics

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Mutations in the Drosophila variable nurse cells (vnc) gene result in female sterility and oogenesis defects, including egg chambers with too many or too few nurse cells. We show that vnc corresponds to Arrest Defective1 (Ard1) and encodes the catalytic subunit of NatA, the major N-terminal acetyl-transferase complex. While N-terminal acetylation is one of the most prevalent covalent protein modifications in eukaryotes, analysis of its role in development has been challenging since mutants that compromise NatA activity have not been described in any multicellular animal. Our data show that reduced ARD1 levels result in pleiotropic oogenesis defects including abnormal cyst encapsulation, desynchronized cystocyte division, disrupted nurse cell chromosome dispersion, and abnormal chorion patterning, consistent with the wide range of predicted NatA substrates. Furthermore, we find that loss of Ard1 affects cell survival/ proliferation and is lethal for the animal, providing the first demonstration that this modification is essential in higher eukaryotes. Developmental Dynamics 239:2813-2827,

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The Drosophila fusome, organelle biogenesis and germ cell differentiation: If you build it…

Cited by 68 publications

References 44 publications

The Fusome Mediates Intercellular Endoplasmic Reticulum Connectivity inDrosophilaOvarian Cysts

The Fusome Mediates Intercellular Endoplasmic Reticulum Connectivity inDrosophilaOvarian Cysts

Bam-dependent deubiquitinase complex can disrupt germ-line stem cell maintenance by targeting cyclin A

Drosophila variable nurse cells encodes arrest defective 1 (ARD1), the catalytic subunit of the major N‐terminal acetyltransferase complex

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