Formation and structure of the fertilization envelope in Xenopus laevis

Grey, Robert D.; Wolf, Don P.; Hedrick, Jerry L.

doi:10.1016/0012-1606(74)90189-4

Cited by 213 publications

(111 citation statements)

References 33 publications

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“…Ca 2ϩ release in eggs results in cortical granule (CG) exocytosis, which releases several enzymes that modify proteins on the egg surface and induces the slow block to polyspermy (21). SOCE channels could be a target for these enzymes, which would explain SOCE inactivation in eggs.…”

Section: Resultsmentioning

confidence: 99%

Store-operated Calcium Entry Inactivates at the Germinal Vesicle Breakdown Stage of Xenopus Meiosis

Machaca

Haun

2000

Journal of Biological Chemistry

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Store-operated calcium entry (SOCE) is the predominant Ca2؉ influx pathway in non-excitable cells and is activated in response to depletion of intracellular Ca 2؉ stores. We have studied SOCE regulation during Xenopus oocyte meiosis. SOCE can be measured readily in stage VI Xenopus oocytes arrested at the G 2 -M transition of the cell cycle, either by Ca 2؉ imaging or by recording the SOCE current. However, following meiotic maturation, SOCE can no longer be activated by store depletion. We have characterized the time course of SOCE inactivation during oocyte maturation, and show that SOCE inactivates almost completely, in a very short time period, at the germinal vesicle breakdown stage of meiosis. This acute inactivation offers an opportunity to better understand SOCE regulation.Ionic calcium (Ca 2ϩ ) is a universal second messenger important for many cellular responses ranging from gene expression to fertilization (1). Ca 2ϩ signaling is mediated by a rise in cytoplasmic Ca 2ϩ , either by Ca 2ϩ release from intracellular stores or Ca 2ϩ influx from the extracellular space. In nonexcitable cells the primary Ca 2ϩ influx pathway is store-operated calcium entry (SOCE) 1 (2). SOCE is activated in response to depletion of intracellular calcium stores and has been implicated in several cellular processes, including T-cell activation (3, 4) and regulation of exocytosis (5-7). However the mechanism(s) coupling store depletion to SOCE activation remain unknown. The following three models have been proposed: "physical coupling," "diffusible messenger," and "vesicle fusion." The physical coupling hypothesis proposes that SOCE channels couple directly to a Ca 2ϩ sensor on the endoplasmic reticulum membrane, possibly the IP 3 receptor, in analogy to the dihydropyridine-ryanodine receptor interaction in skeletal muscle (8 -10). Whereas the diffusible messenger hypothesis argues that store depletion results in the generation of a diffusible messenger that opens SOCE channels (11-13), the vesicle fusion model proposes that SOCE channels are inserted in the plasma membrane following store depletion (14). Although there is some evidence for each model (2), it is not yet clear what the coupling mechanism is and whether SOCE is activated by the same mechanism in different cell types.Despite the importance and ubiquitous nature of Ca 2ϩ signaling pathways, their role and regulation during the cell cycle remain controversial. Probably the clearest example of a Ca 2ϩ requirement during the cell cycle is at fertilization, where a Ca 2ϩ signal is necessary and sufficient for egg activation and the initiation of embryonic development (15, 16). Oocytes of both Xenopus and mammals are arrested at the G 2 -M transition of the cell cycle (15, 17). Before such oocytes become competent to be fertilized and able to support embryonic development, they undergo a maturation process called meiotic (or oocyte) maturation. During this maturation period oocytes enter meiosis, complete the first meiotic division with the extrusion of a polar body,...

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Section: Resultsmentioning

confidence: 99%

Store-operated Calcium Entry Inactivates at the Germinal Vesicle Breakdown Stage of Xenopus Meiosis

Machaca

Haun

2000

Journal of Biological Chemistry

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“…The initial Ca 2þ rise at fertilization gates Ca 2þ -activated Cl À channels, which depolarize the egg membrane (fertilization potential), and block further sperm entry because sperm fusion in Xenopus is voltage-dependent (Jaffe et al, 1983). The slow block is due to Ca 2þ -dependent fusion of cortical granules, which provides the long-term block to polyspermy (Grey et al, 1974;Wolf, 1974). Cortical granules are large vesicles containing various enzymes that modify the egg's extracellular matrix and create a physically impenetrable barrier (fertilization envelope) to sperm (Grey et al, 1976).…”

Section: Physiological Roles Of Ca 2r At Fertilizationmentioning

confidence: 99%

Ca²⁺ signaling differentiation during oocyte maturation

Machaca

2007

Journal Cellular Physiology

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Oocyte maturation is an essential cellular differentiation pathway that prepares the egg for activation at fertilization leading to the initiation of embryogenesis. An integral attribute of oocyte maturation is the remodeling of Ca 2þ signaling pathways endowing the egg with the capacity to produce a specialized Ca 2þ transient at fertilization that is necessary and sufficient for egg activation. Consequently, mechanistic elucidation of Ca 2þ signaling differentiation during oocyte maturation is fundamental to our understanding of egg activation, and offers a glimpse into Ca 2þ signaling regulation during the cell cycle.

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“…The VE of the South African clawed frog, Xenopus laevis, has been well-documented for its functions as a site for polyspermy block (9,10) and binding with sperm (16). Intriguing in relation to its functions in gamete interaction is that certain glycoprotein components of this envelope undergo conversions both before (6) and after (7) fertilization.…”

Section: Introductionmentioning

confidence: 99%

The Synthesis and Localization of Envelope Glycoproteins in Oocytes of Xenopus laevis using Immunocytochemical Methods

1989

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Development Growth & DifferentiationThe site of origin and the mode of differentiation of the coelomic envelope (CE) in growing oocytes of Xenopus laevis were studied using the rabbit antiserum raised against the isolated envelope from oviposited eggs. The antiserum preabsorbed with egg extracts reacted with most components of CE glycoproteins detectable by SDS-PAGE, and stained specifically the CE of full-grown (st. VI) oocytes using indirect immunofluorescence methods. Transmission electron microscopy employing IgG-conjugated colloidal gold demonstrated that the CE antigens were distributed throughout the whole cytoplasm of st. I oocytes, and began to be deposited around the oocyte surface at late st. I. During st. II to VI the density of CE antigens in the oocyte cytoplasm decreased markedly, while the deposition of extracellular CE antigens increased gradually in association with the formation of a fibrillar network. The CE antigens were observed in and around the highly extended oocyte microvilli during st. II to IV, but were never found in follicle cells at any stages of oocyte growth. On western blot analyses, the extracellular CE components appeared first at st. II, and increased both in amount and number of bands during st. Ill -V to attain a typical electrophoretic profiles of well-developed CE. The cytosols of growing oocytes, however, possessed several antigenic components which were distinct from those of extracellular CE, suggesting the occurrence of intracellular precursor molecules for CE. The CEs of st. IV oocytes defolliculated and cultured in [3H] leucine contained certain CE components that expressed the radiolabel on fluorography. These results indicate that in Xenopus laevis the oocyte is directly involved in the synthesis and assembly, as well as secretion of CE with least contribution by the follicle cells.

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Formation and structure of the fertilization envelope in Xenopus laevis

Cited by 213 publications

References 33 publications

Store-operated Calcium Entry Inactivates at the Germinal Vesicle Breakdown Stage of Xenopus Meiosis

Store-operated Calcium Entry Inactivates at the Germinal Vesicle Breakdown Stage of Xenopus Meiosis

Ca²⁺ signaling differentiation during oocyte maturation

The Synthesis and Localization of Envelope Glycoproteins in Oocytes of Xenopus laevis using Immunocytochemical Methods

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Formation and structure of the fertilization envelope in Xenopus laevis

Cited by 213 publications

References 33 publications

Store-operated Calcium Entry Inactivates at the Germinal Vesicle Breakdown Stage of Xenopus Meiosis

Store-operated Calcium Entry Inactivates at the Germinal Vesicle Breakdown Stage of Xenopus Meiosis

Ca2+ signaling differentiation during oocyte maturation

The Synthesis and Localization of Envelope Glycoproteins in Oocytes of Xenopus laevis using Immunocytochemical Methods

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Ca²⁺ signaling differentiation during oocyte maturation