Cumulus expansion initiates physical and developmental autonomy of the oocyte

Zygote ◽  
1996 ◽  
Vol 4 (04) ◽  
pp. 335-341 ◽  
Author(s):  
William J. Larsen ◽  
Lin Chen ◽  
Robert Powers ◽  
Hong Zhang ◽  
Paul T. Russell ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Germ Cell ◽  
Cell Population ◽  
Follicle Cell ◽  
Ovarian Cycle ◽  
Follicle Cells ◽  
Cumulus Expansion ◽  
Primary Oocyte ◽  
Female Germ Cell

As meiosis is initiated and the oogonium is transformed into a primary oocyte, the female germ cell becomes intimately invested by a single squamous layer of sex cord epithelium. As the follicle cell population expands during the initial stages of the ovarian cycle, oocyte and follicle cells become increasingly connected to one another by one of the most extensive populations of gap junctions documented in any epithelium (reviewed in Larsen & Wert, 1988).

Ultrastructural characteristics of the follicle cell-oocyte interface in the oogenesis of Ceratophrys cranwelli

Zygote ◽  
2002 ◽  
Vol 10 (2) ◽  
pp. 163-173 ◽  
Author(s):  
Evelina I. Villecco ◽  
Susana B. Genta ◽  
Alicia N. Sánchez Riera ◽  
Sara S. Sánchez
Keyword(s):  
Plasma Membrane ◽  
Granular Material ◽  
Gap Junctions ◽  
Close Contact ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Apical Surface ◽  
Coated Pits ◽  
Compact Zone ◽  
Vitelline Envelope

In this work we carried out an ultrastructural analysis of the cell interface between oocyte and follicle cells during the oogenesis of the amphibian Ceratophrys cranwelli, which revealed a complex cell-cell interaction. In the early previtellogenic follicles, the plasma membrane of the follicle cells lies in close contact with the plasma membrane of the oocyte, with no interface between them. In the mid-previtellogenic follicles the follicle cells became more active and their cytoplasm has vesicles containing granular material. Their apical surface projects cytoplasmic processes (macrovilli) that contact the oocyte, forming gap junctions. The oocyte surface begins to develop microvilli. At the interface both processes delimit lacunae containing granular material. The oocyte surface has endocytic vesicles that incorporate this material, forming cortical vesicles that are peripherally arranged. In the late previtellogenic follicle the interface contains fibrillar material from which the vitelline envelope will originate. During the vitellogenic period, there is an increase in the number and length of the micro- and macrovilli, which become regularly arranged inside fibrillar tunnels. At this time the oocyte surface exhibits deep crypts where the macrovilli enter, thus increasing the follicle cell-oocyte junctions. In addition, the oocyte displays coated pits and vesicles evidencing an intense endocytic activity. At the interface of the fully grown oocyte the fibrillar network of the vitelline envelope can be seen. The compact zone contains a fibrillar electron-dense material that fills the spaces previously occupied by the now-retracted microvilli. The macrovilli are still in contact with the surface of the oocyte, forming gap junctions.

The Drosophila AP axis is polarised by the cadherin-mediated positioning of the oocyte

Development ◽  
1998 ◽  
Vol 125 (18) ◽  
pp. 3635-3644 ◽  
Author(s):  
A. Gonzalez-Reyes ◽  
D. St Johnston
Keyword(s):  
Germ Cell ◽  
Follicle Cell ◽  
Cell Types ◽  
Follicle Cells ◽  
Cell Rearrangement ◽  
Germline Cyst ◽  
Germline Cells ◽  
Adhesion Complex ◽  
Anterior Posterior ◽  
Anterior Posterior Axis

The anterior-posterior axis of Drosophila originates from two symmetry-breaking steps during early oogenesis. First, one of the two pro-oocytes within the cyst of 16 germline cells is selected to become the oocyte. This cell then comes to lie posterior to the other germline cells of the cyst, thereby defining the polarity of the axis. Here we show that the oocyte reaches the posterior of the cyst in two steps. (1) The cyst flattens as it enters region 2b of the germarium to place the two pro-oocytes in the centre of the cyst, where they contact the posterior follicle cells. (2) One cell is selected to become the oocyte and protrudes into the posterior follicle cell layer when the cyst rounds up on entering region 3. During this germ cell rearrangement, the components of the homophilic cadherin adhesion complex, DE-cadherin, Armadillo and alpha-catenin, accumulate along the border between the oocyte and the posterior follicle cells. Furthermore, the positioning of the oocyte requires cadherin-dependent adhesion between these two cell types, since the oocyte is frequently misplaced when DE-cadherin is removed from either the germline or the posterior follicle cells. We conclude that the oocyte reaches the posterior of the germline cyst because it adheres more strongly to the posterior follicle cells than its neighbours during the germ cell rearrangement that occurs as the cyst moves into region 3. The Drosophila anterior-posterior axis therefore becomes polarised by an unusual cadherin-mediated adhesion between a germ cell and mesodermal follicle cells.

scholarly journals Gap junctions between the oocyte and companion follicle cells in the mammalian ovary.

1976 ◽  
Vol 71 (2) ◽  
pp. 680-686 ◽  
Author(s):  
E Anderson ◽  
D F Albertini
Keyword(s):  
Electron Microscopy ◽  
Gap Junctions ◽  
Functional Significance ◽  
Adult Mouse ◽  
Freeze Fracture ◽  
Follicle Cell ◽  
Neonatal Rat ◽  
Follicle Cells ◽  
Freeze Fracture Electron Microscopy ◽  
Fracture Electron

Tracer and freeze-fracture electron microscopy of the ovaries of neonatal rat and adult mouse, rat, rabbit, and primate have revealed the presence of gap junctions between follicle cells and oocytes. The junctional connections are found at the ends of follicle cell projections which traverse the zona pellucida and terminate upon microvilli and evenly contoured nonmicrovillar regions of the oolemma. Gap junctions are often seen associated with a macula adherens type of junction. The gap junctions occasionally consist of minute ovoid plaques, but nore frequently appear as rectilinear single- or multiple-row aggregates of particles on the P-face or pits on the E-face. The functional significance of follicle cell-oocyte gap junctions is discussed with respect to the regulation of meiosis and luteinization.

Xenopus oocyte K+ current. I. FSH and adenosine stimulate follicle cell-dependent currents

1990 ◽  
Vol 259 (5) ◽  
pp. C775-C783 ◽  
Author(s):  
L. J. Greenfield ◽  
J. T. Hackett ◽  
J. Linden
Keyword(s):  
Protein Kinase ◽  
Gap Junctions ◽  
Adenylyl Cyclase ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Dependent Protein Kinase ◽  
Camp Dependent Protein Kinase ◽  
Large Oocyte ◽  
K Current ◽  
Dependent Protein

Ovarian follicles of Xenopus laevis frogs consist of a single large oocyte surrounded by follicle cells attached to the oocyte by gap junctions. Adenosine has been found to activate an outward K+ current in follicles. This response is reduced by microinjection of protein kinase inhibitor (PKI), suggesting that adenosine 3',5'-cyclic monophosphate (cAMP) mediates the response. To investigate this further, we verified previous studies that indicate that several methods of elevating cAMP in follicles activate hyperpolarizing outward currents. The potency of two adenosine analogues to hyperpolarize follicles, 5'-N-ethylcarboxamidoadenosine (NECA) greater than cyclopentyladenosine, is indicative of A2 receptors that are characteristically coupled to adenylyl cyclase. We also report for the first time that another stimulator of adenylyl cyclase, follicle-stimulating hormone (FSH), also induces a hyperpolarizing current in follicles which is carried by K+ and attenuated by injection of PKI. We used a novel procedure to completely remove follicle cells from oocytes. Intact follicles, but not oocytes completely stripped of follicle cells, hyperpolarized in response to FSH, NECA, dibutyryl cAMP, microinjected cAMP, and forskolin, but not to dideoxyforskolin (which does not activate adenylyl cyclase). Injection of the catalytic subunit of cAMP-dependent protein kinase (which is too large to traverse gap junctions) into oocytes of intact follicles failed to activate a K+ current. These data suggest that FSH and adenosine hyperpolarize follicles by stimulating adenylyl cyclase and that cAMP-dependent protein kinase must be activated on both sides of follicle cell-oocyte gap junctions to elicit a hyperpolarizing K+ current.

Xenopus oocyte K+ current. III. Phorbol esters and pH regulate current at gap junctions

1990 ◽  
Vol 259 (5) ◽  
pp. C792-C800 ◽  
Author(s):  
L. J. Greenfield ◽  
J. T. Hackett ◽  
J. Linden
Keyword(s):  
Gap Junctions ◽  
Phorbol Esters ◽  
Electrical Coupling ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Acid Ph ◽  
Junctional Conductance ◽  
K Current ◽  
Gap Junctional ◽  
K Currents

Xenopus follicles consist of a single large oocyte surrounded by a monolayer of follicle cells attached to the oocyte by gap junctions. Adenosine 3',5'-cyclic monophosphate (cAMP) activates an outward K+ current which is completely abolished if follicle cells are removed or if phorbol esters (which have been reported to reduce gap junctional conductance) are added. In this study we show that phorbol esters do not reduce cAMP levels in follicles and that acid pH, another known stimulus for reducing gap junctional conductance, mimics the action of phorbol esters to inhibit the cAMP-stimulated K+ current. We also examined electrical coupling between oocytes of pairs of follicles placed in physical contact (across 2 oocyte-follicle cell and 1 follicle cell-follicle cell gap junction). Phorbol esters and acid pH (5.5-6.5) decreased electrical coupling without eliciting a shunt current, since slope conductance of current-voltage curves recorded during voltage clamp was simultaneously decreased. Increasing cAMP, which has been reported to enhance gap junctional conductance in mammalian cells, increased slope conductance without decreasing electrical coupling between pairs of follicles. The data suggest that cAMP increases and phorbol esters and acid pH decrease K+ currents at least in part by effects on gap junctions. The effects of phorbol esters and acid pH to reduce electrical coupling between oocytes cannot be due to blockade of K+ channels, since such an action would increase electrical coupling (as verified by computer simulations). These findings are consistent with the idea that cAMP-activated K+ currents originate in follicle cells and are communicated to the oocyte via gap junctions.

Effect of exogenous sex steroids upon the number of germ cells and the growth of foetal ovaries grafted under the kidney capsule of adult ovariectomized hamsters

Development ◽  
1983 ◽  
Vol 78 (1) ◽  
pp. 33-42
Author(s):  
J. Arrau ◽  
L. Roblero ◽  
M. Cury ◽  
R. González
Keyword(s):  
Germ Cell ◽  
Cell Population ◽  
Germ Cells ◽  
Sex Steroids ◽  
Peripheral Circulation ◽  
Absolute Number ◽  
Subcutaneous Injections ◽  
Kidney Capsule ◽  
Specific Effects ◽  
Primary Oocyte

The effect of estradiol E, progesterone P and testosterone propionate T upon growth and germ cell population of foetal ovaries transplanted under the kidney capsule of adult ovariectomized hamsters was examined. Foetal ovaries were obtained 15 days postcoitum and the host received daily subcutaneous injections of E (1 µg/day), P (5 mg/day), T (500 µg/day) or E + P in 0·1 ml oil for 25 days beginning 5 days before grafting. One day after the last injection, the size of the ovary, the germ cell population and plasma steroid levels were assessed. The results of hormone assays indicate that daily steroid administration was able to maintain continuously elevated plasma levels of the corresponding hormone. Interconversions or steroid secretion by the graft, if any, were not reflected in the peripheral circulation. The growth of the graft was stimulated by T and inhibited by P, in comparison with E and oil-treated controls. All germ cells were at the stage of primary oocyte forming part of a primordial or growing follicle. Their absolute number was significantly increased by T and E and significantly decreased by P and E + P. The number of oocytes per mm3 of ovary was increased 80 %, 48 % and 40 % with E, T and E + P, respectively. It is concluded that, in the hamster, exogenous sex steroids given to the host can exert specific effects upon the growth and oocyte population of a grafted foetal ovary. Whether ornot the action of steroids upon the graft is a direct one and whether they influenced oogonial mitosis, the evolution of the meiotic prophase or atresia of primary oocytes remains to be determined.

Memoirs: The Cytopasmic Inclusion of the Germ-Cells

1917 ◽  
Vol s2-62 (247) ◽  
pp. 407-463
Author(s):  
J. BRONTÉ GATENBY
Keyword(s):  
Germ Cell ◽  
Primordial Germ Cell ◽  
Growth Period ◽  
Pieris Brassicae ◽  
Constant Factor ◽  
Cytoplasmic Bodies ◽  
Female Germ Cell ◽  
Probable Nature ◽  
And Function ◽  
Definite Period

(1) In Smerinthus populi, Pieris brassicæ, and a number of other species of moths and butterflies the cytoplasmic bodies have been followed out. (2) The micromitosome lias been followed from the spermatocyte back into the secondary spermatogonium. It is very probably present in the primordial germ-cell. (3) The micromitosome has been definitely found in the female. (4) The micromitosome seems to divide in all divisions, and I consider that it is a constant factor in the spermatids of Smerinthus. (5) The probable nature and function of the micromitosome is discussed. (6) The mitochondria have been carefully examined in the male and female germ-cell in all stages except in the maturation division of the female and in fertilisation. (7) It has been shown that in early stages the cytoplasmic bodies of the female resemble those of the male. (8) There is a definite period, judged to be about the beginning of growth stage, when the subsequent fate of the mitochondria in the male becomes different from that of the female. (9) The remarkable formation of chromophobe and chromophile zones in the male mitochondrial body aud the use of these zones are described. (10) The formation of the macromitosome from the mitochondria is described. (11) The changes undergone by the macromitosome in sperm formation are followed out. (12) The presence of the acroblasts in the fairly early growth period of the spermatocyte is described. (13) The complicated evolutions of these bodies in division of the cells, their subsequent fate and' their probable nature are discussed. (14) The staining and fixing reactions of the cytoplasmic bodies are fully described. (15) A number of abnormalities have been described. (16) The centrosome has been shown to divide in the young spermatid, and one centrosome is probably lost, but definite evidence is not forthcoming.

scholarly journals Mutations that Affect Channel Opening of Innexin Hemichannels in the C. elegans Gonad

2020 ◽  
Author(s):  
Todd Starich ◽  
David Greenstein
Keyword(s):  
Cell Proliferation ◽  
Gap Junctions ◽  
Germ Cell ◽  
Structural Model ◽  
Loss Of Function ◽  
C Elegans ◽  
Somatic Gonad ◽  
Channel Opening ◽  
Germline Proliferation ◽  
Germ Cell Proliferation

In C. elegans, gap junctions couple cells of the somatic gonad with the germline to support germ cell proliferation and gametogenesis. We previously characterized a strong loss-of-function mutation (T239I) affecting the second extracellular loop (EL2) of the somatic INX-8 hemichannel subunit. These mutant hemichannels form non-functional gap junctions with germline-expressed innexins. Here we describe the characterization of mutations that restore germ cell proliferation in the T239I EL2 mutant background. We recovered seven intragenic mutations located in diverse domains of INX-8 but not the EL domains. These second-site mutations compensate for the original channel defect to varying degrees, from nearly complete wild-type rescue, to partial rescue of germline proliferation. One suppressor mutation (E350K) supports the innexin cryo-EM structural model that the channel pore opening is surrounded by a cytoplasmic dome. Two suppressor mutations (S9L and I36N) may form leaky hemichannels that support germline proliferation but cause the demise of somatic sheath cells. Phenotypic analyses of three other suppressors reveal an equivalency in the rescue of germline proliferation and comparable delays in gametogenesis but a graded rescue of fertility. These latter mutations may be useful to probe interactions with the biochemical pathways that produce the molecules transiting through soma-germline gap junctions.

CX43 expression, phosphorylation, and distribution in the normal and autoimmune orchitic testis with a look at gap junctions joining germ cell to germ cell

2011 ◽  
Vol 300 (1) ◽  
pp. R121-R139 ◽  
Author(s):  
R.-Marc Pelletier ◽  
Casimir D. Akpovi ◽  
Li Chen ◽  
Robert Day ◽  
María L. Vitale
Keyword(s):  
Cell Differentiation ◽  
Gap Junctions ◽  
Germ Cell ◽  
Sertoli Cell ◽  
Sertoli Cells ◽  
Seminiferous Tubule ◽  
Connexin 43 ◽  
Cx43 Expression ◽  
Cx43 Protein ◽  
Cx43 Mrna

Spermatogenesis requires connexin 43 (Cx43).This study examines normal gene transcription, translation, and phosphorylation of Cx43 to define its role on germ cell growth and Sertoli cell's differentiation, and identifies abnormalities arising from spontaneous autoimmune orchitis (AIO) in mink, a seasonal breeder and a natural model for autoimmunity. Northern blot analysis detected 2.8- and a 3.7-kb Cx43 mRNA bands in seminiferous tubule-enriched fractions. Cx43 mRNA increased in seminiferous tubule-enriched fractions throughout development and then seasonally with the completion of spermatogenesis. Cx43 protein levels increased transiently during the colonization of the tubules by the early-stage spermatocytes. Cx43 phosphorylated (PCx43) and nonphosphorylated (NPCx43) in Ser368 decreased during the periods of completion of meiosis and Sertoli cell differentiation, while Cx43 mRNA remained elevated throughout. PCx43 labeled chiefly the plasma membrane except by stage VII when vesicles were also labeled in Sertoli cells. Vesicles and lysosomes in Sertoli cells and the Golgi apparatus in the round spermatids were NPCx43 positive. A decrease in Cx43 gene expression was matched by a Cx43 protein increase in the early, not the late, phase of AIO. Total Cx43 and PCx43 decreased with the advance of orchitis. The study makes a novel finding of gap junctions connecting germ cells. The data indicate that Cx43 protein expression and phosphorylation in Ser368 are stage-specific events that may locally influence the acquisition of meiotic competence and the Sertoli cell differentiation in normal testis. AIO modifies Cx43 levels, suggesting changes in Cx43-mediated intercommunication and spermatogenic activity in response to cytokines imbalances in Sertoli cells.

Juvenile hormone increases ouabain-binding capacity of microsomal preparations from vitellogenic follicle cells

1983 ◽  
Vol 61 (7) ◽  
pp. 826-831 ◽  
Author(s):  
T. T. Ilenchuk ◽  
K. G. Davey
Keyword(s):  
Juvenile Hormone ◽  
Binding Capacity ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Follicular Epithelium ◽  
Curvilinear Relationship ◽  
Scatchard Analysis ◽  
Ouabain Binding ◽  
Binding Characteristics ◽  
Brain Microsomes

A comparison has been made of the effects of juvenile hormone (JH) on the binding characteristics for ouabain of microsomes prepared from brain and from cells of the follicular epithelium surrounding previtellogenic or vitellogenic oocytes in Rhodnius. JH has no effect on the binding of ouabain to brain microsomes and decreases the Kd, but does not alter the Bmax for previtellogenic follicle cells. For vitellogenic follicle cells, Scatchard analysis reveals a curvilinear relationship, which is interpreted as indicating that a new population of JH-sensitive ouabain-binding sites develops as the follicle cell enters vitellogenesis. These results are related to earlier data obtained on the effect of JH on ATPase activity, volume changes in isolated follicle cells, and the development of spaces between the cells of the follicular epithelium.

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