A novel pattern of germ cell divisions in the production of hymenopteran insect eggs

Egg development is a defining process of reproduction in higher eukaryotes. In the fruit fly, Drosophila melanogaster , this process begins with four mitotic divisions starting from a single germ cell, producing a cyst of 16 cystocytes; one of these cells will become the oocyte and the others supporting nurse cells. These mitotic divisions are exceptional because cytokinesis is incomplete, resulting in the formation of cytoplasmic bridges known as ring canals that interconnect the cystocytes. This organization allows all cystocytes to divide synchronously during each mitotic round, resulting in a final, power-of-2 number of germ cells. Given that numerous insects obey this power-of-2 rule, we investigated if strict cell doubling is a universal, underlying cause. Using confocal microscopy, we found striking departures from this paradigm in three different power-of-2 insects belonging to the Apocrita suborder (ants, bees and wasps). In these insects, the earliest-formed cystocytes cease to divide during the latter mitotic cycles while their descendants undergo further division, thereby producing a ‘radial’ direction of division activity. Such cystocyte division patterns that depart from strict cell doubling may be ‘fine-tuned’ in order to maintain a final, power-of-2 germ cell number.

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Müllerian Inhibiting Substance Is Required for Germ Cell Proliferation during Early Gonadal Differentiation in Medaka (Oryzias latipes)

Endocrinology ◽

10.1210/en.2007-1535 ◽

2007 ◽

Vol 149 (4) ◽

pp. 1813-1819 ◽

Cited By ~ 47

Author(s):

Eri Shiraishi ◽

Norifumi Yoshinaga ◽

Takeshi Miura ◽

Hayato Yokoi ◽

Yuko Wakamatsu ◽

...

Keyword(s):

Cell Proliferation ◽

Germ Cell ◽

Germ Cells ◽

Sex Differentiation ◽

Somatic Cells ◽

Oryzias Latipes ◽

Cell Number ◽

Gonadal Differentiation ◽

Loss Of Function ◽

Germ Cell Proliferation

Müllerian inhibiting substance (MIS) is a glycoprotein belonging to the TGF-β superfamily. In mammals, MIS is responsible for the regression of Müllerian ducts in the male fetus. However, the role of MIS in gonadal sex differentiation of teleost fish, which have no Müllerian ducts, has yet to be clarified. In the present study, we examined the expression pattern of mis and mis type 2 receptor (misr2) mRNAs and the function of MIS signaling in early gonadal differentiation in medaka (teleost, Oryzias latipes). In situ hybridization showed that both mis and misr2 mRNAs were expressed in the somatic cells surrounding the germ cells of both sexes during early sex differentiation. Loss-of-function of either MIS or MIS type II receptor (MISRII) in medaka resulted in suppression of germ cell proliferation during sex differentiation. These results were supported by cell proliferation assay using 5-bromo-2′-deoxyuridine labeling analysis. Treatment of tissue fragments containing germ cells with recombinant eel MIS significantly induced germ cell proliferation in both sexes compared with the untreated control. On the other hand, culture of tissue fragments from the MIS- or MISRII-defective embryos inhibited proliferation of germ cells in both sexes. Moreover, treatment with recombinant eel MIS in the MIS-defective embryos dose-dependently increased germ cell number in both sexes, whereas in the MISRII-defective embryos, it did not permit proliferation of germ cells. These results suggest that in medaka, MIS indirectly stimulates germ cell proliferation through MISRII, expressed in the somatic cells immediately after they reach the gonadal primordium.

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Germ cell fate and seminiferous tubule development in bovine testis xenografts

Reproduction ◽

10.1530/rep.1.00912 ◽

2005 ◽

Vol 130 (6) ◽

pp. 923-929 ◽

Cited By ~ 54

Author(s):

Rahul Rathi ◽

Ali Honaramooz ◽

Wenxian Zeng ◽

Stefan Schlatt ◽

Ina Dobrinski

Keyword(s):

Germ Cell ◽

Cell Fate ◽

Germ Cells ◽

Cell Number ◽

Sperm Production ◽

Continuous Increase ◽

Control Tissue ◽

Low Efficiency ◽

Pachytene Spermatocytes ◽

Testis Tissue

Spermatogenesis can occur in testis tissue from immature bulls ectopically grafted into mouse hosts; however, efficiency of sperm production is lower than in other donor species. To elucidate a possible mechanism for the impaired spermatogenesis in bovine testis xenografts, germ cell fate and xenograft development were investigated at different time points and compared with testis tissue from age-matched calves as controls. Histologically, an initial decrease in germ cell number was noticed in xenografts recovered up to 2 months post-grafting without an increase in germ cell apoptosis. From 2 months onward, the number of germ cells increased. In contrast, a continuous increase in germ cell number was seen in control tissue. Pachytene spermatocytes were observed in some grafts before 4 months, whereas in the control tissue they were not present until 5 months of age. Beyond 4 months post-grafting spermatogenesis appeared to be arrested at the pachytene spermatocyte stage in most grafts. Elongated spermatids were observed between 6 and 8 months post-grafting, similar to the controls, albeit in much lower numbers. Lumen formation started earlier in grafts compared with controls and by 6 months post-grafting tubules with extensively dilated lumen were observed. A donor effect on efficiency of spermatogenesis was also observed. These results indicate that the low efficiency of sperm production in bovine xenografts is due to an initial deficit of germ cells and impaired meiotic and post-meiotic differentiation. The characterization of spermatogenic efficiency will provide the basis to understand the control of spermatogenesis in testis grafts.

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A Dual Role for Actin and Microtubule Cytoskeleton in the Transport of Golgi Units from the Nurse Cells to the Oocyte Across Ring Canals

Molecular Biology of the Cell ◽

10.1091/mbc.e08-04-0360 ◽

2009 ◽

Vol 20 (1) ◽

pp. 556-568 ◽

Cited By ~ 13

Author(s):

Emmanuelle Nicolas ◽

Nicolas Chenouard ◽

Jean-Christophe Olivo-Marin ◽

Antoine Guichet

Keyword(s):

Embryonic Development ◽

Transport Process ◽

Myosin Ii ◽

Nurse Cells ◽

Transport Mechanisms ◽

Step Process ◽

Actin Networks ◽

Ring Canals ◽

Cytoplasmic Bridges ◽

Active Transport Process

Axis specification during Drosophila embryonic development requires transfer of maternal components during oogenesis from nurse cells (NCs) into the oocyte through cytoplasmic bridges. We found that the asymmetrical distribution of Golgi, between nurse cells and the oocyte, is sustained by an active transport process. We have characterized actin basket structures that asymmetrically cap the NC side of Ring canals (RCs) connecting the oocyte. Our results suggest that these actin baskets structurally support transport mechanisms of RC transit. In addition, our tracking analysis indicates that Golgi are actively transported to the oocyte rather than diffusing. We observed that RC transit is microtubule-based and mediated at least by dynein. Finally, we show that actin networks may be involved in RC crossing through a myosin II step process, as well as in dispatching Golgi units inside the oocyte subcompartments.

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The Arp2/3 complex and the formin, Diaphanous, are both required to regulate the size of germline ring canals in the developing egg chamber

10.1101/813873 ◽

2019 ◽

Author(s):

Josephine Thestrup ◽

Marina Tipold ◽

Alexandra Kindred ◽

Kara Stark ◽

Travis Curry ◽

...

Keyword(s):

Fruit Fly ◽

Actin Binding ◽

Nurse Cells ◽

Intercellular Bridge ◽

Ring Canal ◽

Contractile Ring ◽

Intercellular Bridges ◽

Large Size ◽

Ring Canals ◽

Egg Chamber

AbstractIntercellular bridges are an essential structural feature found in both germline and somatic cells throughout the animal kingdom. Because of their large size, the germline intercellular bridges, or ring canals, in the developing fruit fly egg chamber are an excellent model to study the formation, stabilization, and expansion of these structures. Within the egg chamber, the germline ring canals connect 15 supporting nurse cells to the developing oocyte, facilitating the transfer of materials required for successful oogenesis. The ring canals are derived from a stalled actomyosin contractile ring; once formed, additional actin and actin-binding proteins are recruited to the ring to support the 20-fold expansion that accompanies oogenesis. These behaviors provide a unique model system to study the actin regulators that control incomplete cytokinesis, intercellular bridge formation, and expansion. By temporally controlling their expression in the germline, we have demonstrated that the Arp2/3 complex and the formin, Diaphanous (Dia), coordinately regulate ring canal size and expansion throughout oogenesis. Dia is required for successful incomplete cytokinesis and the initial stabilization of the germline ring canals. Once the ring canals have formed, the Arp2/3 complex and Dia cooperate to determine ring canal size and maintain their stability. Our data suggest that the nurse cells must maintain a precise balance between the activity of these two nucleators during oogenesis.

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Quantification of healthy and atretic germ cells and follicles in the developing and post-natal ovary of the South American plains vizcacha, Lagostomus maximus: evidence of continuous rise of the germinal reserve

Reproduction ◽

10.1530/rep-13-0455 ◽

2014 ◽

Vol 147 (2) ◽

pp. 199-209 ◽

Cited By ~ 11

Author(s):

P I F Inserra ◽

N P Leopardo ◽

M A Willis ◽

A L Freysselinard ◽

A D Vitullo

Keyword(s):

Germ Cell ◽

Germ Cells ◽

Germ Line ◽

Cell Number ◽

South American ◽

The South ◽

Foetal Life ◽

Female Germ Line ◽

Lagostomus Maximus ◽

Mitotic Proliferation

The female germ line in mammals is subjected to massive cell death that eliminates 60–85% of the germinal reserve by birth and continues from birth to adulthood until the exhaustion of the germinal pool. Germ cell demise occurs mainly through apoptosis by means of a biased expression in favour of pro-apoptotic members of theBCL2gene family. By contrast, the South American plains vizcacha,Lagostomus maximus, exhibits sustained expression of the anti-apoptoticBCL2gene throughout gestation and a low incidence of germ cell apoptosis. This led to the proposal that, in the absence of death mechanisms other than apoptosis, the female germ line should increase continuously from foetal life until after birth. In this study, we quantified all healthy germ cells and follicles in the ovaries ofL. maximusfrom early foetal life to day 60 after birth using unbiased stereological methods and detected apoptosis by labelling with TUNEL assay. The healthy germ cell population increased continuously from early-developing ovary reaching a 50 times higher population number by the end of gestation. TUNEL-positive germ cells were <0.5% of the germ cell number, except at mid-gestation (3.62%). Mitotic proliferation, entrance into prophase I stage and primordial follicle formation occurred as overlapping processes from early pregnancy to birth. Germ cell number remained constant in early post-natal life, but a remnant population of non-follicular VASA- and PCNA-positive germ cells still persisted at post-natal day 60.L. maximusis the first mammal so far described in which female germ line develops in the absence of constitutive massive germ cell elimination.Free Spanish abstractSpanish translation of this abstract is freely available athttp://www.reproduction-online.org/content/147/2/199/suppl/DC1

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A sex-specific number of germ cells in embryonic gonads of Drosophila

Development ◽

10.1242/dev.121.6.1867 ◽

1995 ◽

Vol 121 (6) ◽

pp. 1867-1873 ◽

Cited By ~ 4

Author(s):

M. Poirie ◽

E. Niederer ◽

M. Steinmann-Zwicky

Keyword(s):

Germ Cell ◽

Germ Cells ◽

Developmental Stages ◽

Control Mechanism ◽

Cell Number ◽

Male And Female ◽

First Instar ◽

Specific Number ◽

Specific Control ◽

Time Point

Male first instar larvae possess more germ cells in their gonads than female larvae of the same stage. To determine the earliest time point of sexual dimorphism in germ cell number, we have counted the germ cells of sexed embryos at different developmental stages. We found no difference in germ cell number of male and female embryos at the blastoderm and early gastrulation stage, or when germ cells are about to exit the midgut pocket. We find, however, that males have significantly more germ cells than females as soon as the germ cells are near the places where the gonads are formed and in all later stages. Our results show that germ cells are subject to a sex-specific control mechanism that regulates the number of germ cells already in embryos.

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The Drosophila stonewall gene encodes a putative transcription factor essential for germ cell development

Development ◽

10.1242/dev.122.3.937 ◽

1996 ◽

Vol 122 (3) ◽

pp. 937-950 ◽

Cited By ~ 1

Author(s):

K.A. Clark ◽

D.M. McKearin

Keyword(s):

Germ Cell ◽

Germ Cells ◽

Nuclear Protein ◽

Cell Development ◽

Nurse Cells ◽

Cell Specification ◽

Germ Cell Development ◽

Specialized Nurse ◽

Putative Transcription Factor ◽

Oocyte Differentiation

The differentiation of Drosophila germ cells is a useful model for studying mechanisms of cell specification. We report the identification of a gene, stonewall, that is required for germ cell development. Mutations in stonewall block proper oocyte differentiation and frequently cause the presumptive oocyte to develop as a nurse cell. Eventually, germ cells degenerate apoptotically. Stonewall is a germ cell nuclear protein; Stonewall has a DNA binding domain that shows similarities to the Myb and Adf-1 transcription factors and has other features that suggest that it is a transcription activating factor. We suggest that Stonewall transcriptional regulation is essential in cystocytes for maturation into specialized nurse cells and oocyte.

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Inactivation of CUG-BP1/CELF1 Causes Growth, Viability, and Spermatogenesis Defects in Mice

Molecular and Cellular Biology ◽

10.1128/mcb.01009-06 ◽

2006 ◽

Vol 27 (3) ◽

pp. 1146-1157 ◽

Cited By ~ 75

Author(s):

Chantal Kress ◽

Carole Gautier-Courteille ◽

H. Beverley Osborne ◽

Charles Babinet ◽

Luc Paillard

Keyword(s):

Germ Cell ◽

Germ Cells ◽

Leydig Cells ◽

Rna Binding ◽

Rna Binding Protein ◽

Cell Number ◽

Pcr Analysis ◽

Wild Type ◽

Mammalian Development ◽

Males And Females

ABSTRACT CUG-BP1/CELF1 is a multifunctional RNA-binding protein involved in the regulation of alternative splicing and translation. To elucidate its role in mammalian development, we produced mice in which the Cugbp1 gene was inactivated by homologous recombination. These Cugbp1 − / − mice were viable, although a significant portion of them did not survive after the first few days of life. They displayed growth retardation, and most Cugbp1 − / − males and females exhibited impaired fertility. Male infertility was more thoroughly investigated. Histological examination of testes from Cugbp1 − / − males showed an arrest of spermatogenesis that occurred at step 7 of spermiogenesis, before spermatid elongation begins, and an increased apoptosis. A quantitative reverse transcriptase PCR analysis showed a decrease of all the germ cell markers tested but not of Sertoli and Leydig markers, suggesting a general decrease in germ cell number. In wild-type testes, CUG-BP1 is expressed in germ cells from spermatogonia to round spermatids and also in Sertoli and Leydig cells. These findings demonstrate that CUG-BP1 is required for completion of spermatogenesis.

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Restoration of spermatogenesis by high levels of testosterone in hypophysectomized rats after long-term regression

Acta Endocrinologica ◽

10.1530/acta.0.1160433 ◽

1987 ◽

Vol 116 (4) ◽

pp. 433-444 ◽

Cited By ~ 29

Author(s):

H. F. S. Huang ◽

G. R. Marshall ◽

R. Rosenberg ◽

E. Nieschlag

Keyword(s):

Germ Cell ◽

Normal Control ◽

Germ Cells ◽

Cell Number ◽

Testis Weight ◽

The Status ◽

Hypophysectomized Rats ◽

Normal Spermatogenesis ◽

Successive Generations

Abstract. In order to correlate the levels of intratesticular testosterone and the status of spermatogenesis, the present study examined the spermatogenic responses of mature chronically hypophysectomized (HPX) rats to different regimens of testosterone (T) replacement, i.e. implantation of a 2 × 5 or 6 × 5 cm long testosterone capsule (TC), or injection of 25 mg or 100 mg of testosterone enanthate (TE) every 4 days for 90 days. These regimens restored the testicular testosterone of the HPX rats to 25–96% of that measured in normal control rats. The testis weight of untreated HPX rats was below 30% of the normal control values. It was restored to 60–80% of control values in the TC implanted rats and to 50% in those receiving TE injection. Complete spermatogenesis of HPX rats was restored in those receiving TC implants and 100 mg TE injections. It was incomplete in those given 25 mg TE injections. Quantitative evaluation of germ cells revealed that spermatogonial populations of HPX rats were restored to 70 and 50% of the normal levels in rats receiving TC implants and TE injection, respectively. Differentiation of these cells resulted in the population of preleptotene spermatocytes to the same extent as those observed in spermatogonia. The yield of spermatids in both TC- and TE-treated HPX rats was below 50% of normal controls. Ratios between two successive generations of germ cells in stage VII epithelium revealed both dosage and regimen effects upon the yield of meiotic cells and spermatids. These results suggest that both T concentration and the mode of T availability to the testis may be important for specific steps of germ cell development in different stages of the cycle of the seminiferous epithelium. The results of the present study demonstrate that as little as 25% of normal testicular T concentration is sufficient to support all stages of spermatogenesis. Failure to restore a normal germ cell number even in the presence of a normal testicular T concentration suggests the need of other factors for quantitative spermatogenesis. Furthermore, despite a higher testicular T concentration achieved by TE injections, the restoration of spermatogenesis was less pronounced by this regimen. This finding suggests that the consistency of testicular T may also be important for normal spermatogenesis.

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Short stop is a gatekeeper at the ring canals of Drosophila ovary

10.1101/2020.12.09.418046 ◽

2020 ◽

Author(s):

Wen Lu ◽

Margot Lakonishok ◽

Vladimir I. Gelfand

Keyword(s):

Actin Filaments ◽

Cytoskeletal Proteins ◽

Nurse Cells ◽

Cellular Functions ◽

Oocyte Growth ◽

Ring Canals ◽

Cytoplasmic Bridges ◽

Drosophila Ovary ◽

Open Nature ◽

Sister Cells

SUMMARYMicrotubules and actin filaments are two major cytoskeletal components essential for a variety of cellular functions. Spectraplakins are a family of large cytoskeletal proteins cross-linking microtubules and actin filaments among other components. In this study, we aim to understand how Short stop (Shot), the single Drosophila spectraplakin, coordinates microtubules and actin filaments for oocyte growth. The oocyte growth completely relies on the acquisition of cytoplasmic materials from the interconnected sister cells (nurse cells), through ring canals, cytoplasmic bridges that remained open after incomplete germ cell division. Given the open nature of the ring canals, it is unclear how the direction of transport through the ring canal is controlled. Here we show that Shot controls the directionality of flow of material from the nurse cells towards the oocyte. Knockdown of shot changes the direction of transport of many types of cargo through the ring canals from unidirectional (toward the oocyte) to bidirectional, resulting in small oocytes that fail to grow over time. In agreement with this flow-directing function of Shot, we find that it is localized at the asymmetric actin fibers adjacent to the ring canals at the nurse cell side, and controls the uniform polarity of microtubules located in the ring canals connecting the nurse cells and the oocyte. Together, we propose that Shot functions as a gatekeeper directing the material flow from the nurse cells to the oocyte, via organization of microtubule tracks.

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