Microtubules In Oocytes Research Articles

Colchicine inhibits GABA A receptors independently of microtubule depolymerization

Colchicine is a microtubule depolymerizing agent used extensively in the study of cytoskeleton-dependent cell functions. In studying the possible functional interaction between the GABA A receptor and the cytoskeleton, we found that colchicine inhibits GABA A receptor function by mechanisms independent of microtubule depolymerization. Human GABA A receptor α1 β2 γ2L subunits were co-expressed in Xenopus oocytes and the effects of colchicine on GABA A receptor function was assessed using the two-electrode voltage-clamp technique. Co-application of GABA (10 μM) with colchicine (100 μM) resulted in a 59.9% inhibition of GABA-gated chloride currents. This effect was instantaneous in onset with no pre-incubation required and reversed within seconds. Other depolymerizing agents, such as nocodazole (20 μM) and vinblastine (200 μM), did not affect GABA A receptor function using the same co-application protocol used with colchicine. The polymerizing agent taxol (10–50 μM) did not affect colchicine inhibition of the GABA responses and did not itself alter GABA-gated chloride currents. The inhibitory effect of colchicine was present under conditions in which the oocyte microtubules had been depolymerized by cold temperature. These results indicate that colchicine inhibits the GABA A receptor via mechanisms unrelated to microtubule depolymerization. To further examine the inhibitory effect of colchicine on the GABA response, GABA (10–3000 μM) concentration-response curves were performed in the absence or presence of various concentrations of colchicine (30–300 μM). In the presence of colchicine, the GABA concentration-response curve was shifted to the right in a parallel fashion. A Schild plot of this data yielded a linear slope indicating that colchicine acts as a competitive antagonist at the GABA binding site. We conclude that colchicine is a competitive antagonist at the GABA A receptor and that studies using colchicine to examine the functional interaction between GABA A receptors and microtubules should be interpreted with caution.

Assembly of nuclear pore complexes and annulate lamellae promotes normal pronuclear development in fertilized mammalian oocytes

ABSTRACT In addition to functional nuclear pore complexes engaged in nucleo-cytoplasmic transport, the cytoplasmic stacks of pore complexes, called annulate lamellae, exist in numerous cell types. Although both annulate lamellae and nuclear pore complexes are present in fertilized mammalian oocytes, their relative roles in the process of fertilization and preimplantation development are not known. Using epifluorescence and electron microscopy, we explored their fate during bovine fertilization. The assembly of annulate lamellae in bovine oocytes was triggered by sperm-oocyte binding and continued concomitantly with the incorporation of the nuclear pores in the nuclear envelopes of the developing male and female pronuclei. This process was also induced by the parthenogenetic activation of metaphase-II-arrested oocytes. Depletion of Ca2+, previously implicated in oocyte activation and in the insertion of pore complexes into the nuclear envelope, prevented the formation of nuclear pore complexes, but not the assembly of annulate lamellae in oocyte cytoplasm. Injection of the nuclear pore antagonist, wheat germ agglutinin, into the cytoplasm of mature oocytes that were subsequently fertilized caused the arrest of pronuclear development, indicating the requirement of nuclear pore complexes for normal pronuclear development. Treatment of the fertilized oocytes with the microtubule inhibitor, nocodazole, prevented gathering of annulate lamellae around the developing pronuclei, insertion of nuclear pores into their nuclear envelopes, and further pronuclear development. The formation of the male pronuclei was reconstituted in Xenopus egg extracts and reflected the behavior of nuclear pores during natural fertilization. These data suggest that nuclear pore complexes are required for normal pronuclear development from its beginning up until pronuclear apposition. Annulate lamellae may be involved in the turnover of nuclear pore complexes during fertilization, which is in turn facilitated by the reorganization of oocyte microtubules and influx of Ca2+ into oocyte cytoplasm.

Assembly of nuclear pore complexes and annulate lamellae promotes normal pronuclear development in fertilized mammalian oocytes.

In addition to functional nuclear pore complexes engaged in nucleo-cytoplasmic transport, the cytoplasmic stacks of pore complexes, called annulate lamellae, exist in numerous cell types. Although both annulate lamellae and nuclear pore complexes are present in fertilized mammalian oocytes, their relative roles in the process of fertilization and preimplantation development are not known. Using epifluorescence and electron microscopy, we explored their fate during bovine fertilization. The assembly of annulate lamellae in bovine oocytes was triggered by sperm-oocyte binding and continued concomitantly with the incorporation of the nuclear pores in the nuclear envelopes of the developing male and female pronuclei. This process was also induced by the parthenogenetic activation of metaphase-II-arrested oocytes. Depletion of Ca2+, previously implicated in oocyte activation and in the insertion of pore complexes into the nuclear envelope, prevented the formation of nuclear pore complexes, but not the assembly of annulate lamellae in oocyte cytoplasm. Injection of the nuclear pore antagonist, wheat germ agglutinin, into the cytoplasm of mature oocytes that were subsequently fertilized caused the arrest of pronuclear development, indicating the requirement of nuclear pore complexes for normal pronuclear development. Treatment of the fertilized oocytes with the microtubule inhibitor, nocodazole, prevented gathering of annulate lamellae around the developing pronuclei, insertion of nuclear pores into their nuclear envelopes, and further pronuclear development. The formation of the male pronuclei was reconstituted in Xenopus egg extracts and reflected the behavior of nuclear pores during natural fertilization. These data suggest that nuclear pore complexes are required for normal pronuclear development from its beginning up until pronuclear apposition. Annulate lamellae may be involved in the turnover of nuclear pore complexes during fertilization, which is in turn facilitated by the reorganization of oocyte microtubules and influx of Ca2+ into oocyte cytoplasm.

High production of nondisjunction mutants in the offspring ofDrosophila melanogaster females exposed to carbon dioxide at meiosis I

Drosophila melanogaster females homozygous for X-linked recessive markers, y and wi, were exposed to CO2 and mated with y+ w+/Y males. The progeny were sampled and inspected for y wi/y wi/Y (XXY) and y+ w+/O (XO) mutants. The frequency of nondisjunction XXY mutants after a 90-min exposure to CO2 increased 100-fold above the control level in the first-day brood but did not increase above the control level in the second to sixth broods, showing that CO2 is an extremely potent inducer of nondisjunction in mature oocytes during meiotic metaphase I but is not harmful to immature oocytes. Nondisjunction-causing damage induced by CO2 in mature oocytes disappeared completely within one day after CO2 treatment, as evidenced by a reduction of the number of XXY mutants to the control level when the mating of CO2-treated females was delayed by one day. CO2-induced nondisjunction is probably due to damage to spindle microtubules in mature oocytes at metaphase I. N2 is a less potent inducer of nondisjunction than CO2. Maternal X-irradiation with 4 Gy did not induce XXY mutants, showing that medium-level radiation does not induce nondisjunction. The results support Gaulden's hypothesis that oxygen deficits and CO2 increases in the microenvironment of mature oocytes can be potent inducers of nondisjunction. The possible relationship to the cluster of Down syndrome seen in Berlin shortly after the Chernobyl accident is discussed.

O-066. Microtubule and chromosome configurations in human oocytes failing to fertilize after ICSI

O-066. Microtubule and chromosome configurations in human oocytes failing to fertilize after ICSI

The Organization and Animal–Vegetal Asymmetry of Cytokeratin Filaments in Stage VIXenopusOocytes Is Dependent upon F-Actin and Microtubules

Confocal immunofluorescence microscopy with anti-cytokeratin antibodies revealed a continuous and polarized network of cytokeratin (CK) filaments in the cortex of stage VIXenopusoocytes. In the animal cortex, CK filaments formed a dense meshwork that both was thicker and exhibited a finer mesh than the network of CK filaments previously observed in the vegetal cortex (Klymkowskyet al.,1987). CK filaments first appeared in association with germinal vesicle (GV) and mitochondrial mass (MM) of oocytes in early mid stage I, indicating that CK filaments are the last of the three cytoskeletal networks to be assembled. By late stage I, CK filaments formed complex networks surrounding the GV, surrounding and penetrating the MM, and linking these networks to a meshwork of CK filaments in the oocyte cortex. During stage III–early IV, CK filaments formed a highly interconnected, apparently unpolarized, radial array linking the perinuclear and cortical CK filament networks. Polarization of the CK filament network was observed during mid stage IV–stage V, as first the animal, then the vegetal CK filament networks adopted the organization characteristic of stage VI oocytes. Treatment of stage VI oocytes with cytochalasin B disrupted the organization of both cortical and cytoplasmic CK filaments, releasing CK filaments from the oocyte cortex and inducing formation of numerous cytoplasmic CK filament aggregates. CB also disrupted the organization of cytoplasmic microtubules (MTs) in stage VI oocytes. Disassembly of oocyte MTs with nocodazole resulted in loss of the characteristic A–V polarity of the cortical CK filament network. In contrast, disruption of cytoplasmic CK filaments by microinjection of anti-CK antibodies had no apparent effect on cytoplasmic or MT organization. We propose a model in which the organization and polarization of the cortical network of CK filaments in stage VIXenopusoocytes are dependent upon a hierarchy of interactions with actin filaments and microtubules.

Microtubule and microfilament dynamics in porcine oocytes during meiotic maturation

Microtubule and microfilament organization in porcine oocytes during maturation in vivo and in vitro was imaged by immunocytochemistry and laser scanning confocal microscopy. At the germinal vesicle stage, microtubules were not detected in the oocyte. After germinal vesicle breakdown, a small microtubule aster was observed near the condensed chromatin. During the prometaphase stage, microtubule asters were found in association with each chromatin mass. The asters then elongated and encompassed the chromatin at the metaphase-I stage. At anaphase-I and telophase-I microtubules were detected in the meiotic spindle. Microtubules were observed only in the second meiotic spindle at the metaphase-II stage. The meiotic spindle was a symmetric, barrel-shaped structure containing anastral broad poles, located peripherally and radially oriented. Taxol, a microtubule-stabilizing agent, did not induce microtubules in oocytes at the germinal vesicle stage. After germinal vesicle breakdown, numerous cytoplasmic foci of microtubules were formed in the entire oocyte when oocytes were incubated in the presence of taxol. Microfilaments were observed as a relatively thick uniform area around the cell cortex and were also found throughout the cytoplasm of oocytes at the germinal vesicle stage. After germinal vesicle breakdown, the microfilaments were concentrated close to the female chromatin. During prometaphase, microfilaments were chromatin moved to the peripheral position. At metaphase-I, two domains, a thick and a thin microfilament area, existed in the egg cortex. Chromosomes were located in the thick microfilament domain of the cortex. In summary, these results suggest that both micro-tubules and microfilaments are closely involved with chromosomal dynamics after germinal vesicle breakdown and during meiotic maturation in porcine oocytes. © 1996 Wiley-Liss, Inc.

Microtubule and microfilament dynamics in porcine oocytes during meiotic maturation.

Microtubule and microfilament organization in porcine oocytes during maturation in vivo and in vitro was imaged by immunocytochemistry and laser scanning confocal microscopy. At the germinal vesicle stage, microtubules were not detected in the oocyte. After germinal vesicle breakdown, a small microtubule aster was observed near the condensed chromatin. During the prometaphase stage, microtubule asters were found in association with each chromatin mass. The asters then elongated and encompassed the chromatin at the metaphase-I stage. At anaphase-I and telophase-I microtubules were detected in the meiotic spindle. Microtubules were observed only in the second meiotic spindle at the metaphase-II stage. The meiotic spindle was a symmetric, barrel-shaped structure containing anastral broad poles, located peripherally and radially oriented. Taxol, a microtubule-stabilizing agent, did not induce microtubules in oocytes at the germinal vesicle stage. After germinal vesicle breakdown, numerous cytoplasmic foci of microtubules were formed in the entire oocyte when oocytes were incubated in the presence of taxol. Microfilaments were observed as a relatively thick uniform area around the cell cortex and were also found throughout the cytoplasm of oocytes at the germinal vesicle stage. After germinal vesicle breakdown, the microfilaments were concentrated close to the female chromatin. During prometaphase, microfilaments were chromatin moved to the peripheral position. At metaphase-I, two domains, a thick and a thin microfilament area, existed in the egg cortex. Chromosomes were located in the thick microfilament domain of the cortex. In summary, these results suggest that both microtubules and microfilaments are closely involved with chromosomal dynamics after germinal vesicle breakdown and during meiotic maturation in porcine oocytes.

Microtubule and microfilament dynamics in porcine oocytes during meiotic maturation

Microtubule and microfilament dynamics in porcine oocytes during meiotic maturation

Vg1 RNA binding protein mediates the association of Vg1 RNA with microtubules in Xenopus oocytes.

Localized RNAs are found in a variety of somatic and developing cell types. In many cases, microtubules have been implicated as playing a role in facilitating transport of these RNAs. Here we report that Vg1 RNA, which is localized to the vegetal cortex of Xenopus laevis oocytes, is associated with microtubules in vivo. Because of the ubiquitous nature of tubulin, the association of specific RNAs with microtubules is likely to involve factors that recognize both RNA and microtubules. Vg1 RNA binding protein (Vg1 RBP), previously shown to bind with high affinity to the vegetal localization site in Vg1 RNA, appears to function in this capacity. Vg1 RBP is associated with microtubules: it is enriched in microtubule extracts of oocytes and is also co-precipitated by heterologous, polymerized tubulin. Furthermore, Vg1 RBP binding activity is required for the specific association of Vg1 RNA to microtubules in vitro. These data suggest a general model for how specific RNAs can be localized to particular sites via common cytoskeletal elements.

γ-Tubulin Is Asymmetrically Distributed in the Cortex of Xenopus Oocytes

Stage VI Xenopus oocytes contain an extensive network of cytoplasmic microtubules (MTs), with no evidence of a functional centrosome. Recently, Stearns et al. (1991) demonstrated that Xenopus eggs contain a substantial pool of the centrosomal protein γ-tublin (γ-Tb). For this report, I have used confocal immunofluorescence microscopy to examine the distribution of γ-Tb during the later stages of oogenesis in Xenopus laevis. γ-Tb was apparent surrounding the germinal vesicle (GV) of stage VI oocytes, consistent with previous results suggesting that the GV serves as an microtubule organizing center in later oogenesis. Surprisingly, γ-Tb was also concentrated in the cortex of stage VI oocytes, and the distribution of cortical γ-Tb was polarized along the animal-vegetal (A-V) axis. In the vegetal cortex, γ-Tb was observed in brightly stained foci, often organized into short linear arrays. In the animal hemisphere, γ-Tb was more evenly distributed as small cortical foci. Dual immunofluorescence microscopy revealed that γ-Tb in the vegetal hemisphere was associated with MTs in the cortical cytoplasm. The distribution of γ-Tb was not significantly affected by either cold or nocodazole, but was partially disrupted by cytochalasin B. γ-Tb thus may serve as a link between the oocyte MT network and cortical actin. Finally, polarization of the distribution of cortical γ-Tb temporally coincides with formation of the A-V axis and polarization of the oocyte MT cytoskeleton during stage IV of oogenesis. These observations raise a number of questions regarding the organization and orientation of MTs during Xenopus oogenesis and the role of γ-Tb in the polarization of the oocyte cytoskeleton during A-V axis formation.

Association of p34cdc2/cyclin B complex with microtubules in starfish oocytes.

The microtubular cytoskeleton exhibits a dramatic reorganization, progressing from interphase radial arrays to a mitotic spindle at the G2/M transition. Although this reorganization has been suspected to be caused by maturation promoting factor (MPF: p34cdc2/cyclin B complex), little is known about how p34cdc2 kinase controls microtubule networks. We provide evidence of the direct association of the p34cdc2/cyclin B complex with microtubules in starfish oocytes. Anti-cyclin B staining of detergent-treated oocytes, isolated asters and meiotic spindles revealed fluorescence associated with microtubule fibers, chromosomes and centrosomes. Microtubules prepared from starfish oocytes were associated with cyclin B and p34cdc2 proteins. Microtubule-bound p34cdc2 and cyclin B were released from microtubules by a high-salt solution and possessed a complex form as shown by the adsorption to suc1-beads and by immunoprecipitation with the anti-cyclin B antibody. The p34cdc2/cyclin B complex associated to microtubules had high histone H1 kinase activity at meiotic metaphase. However, it was not necessary for the p34cdc2/cyclin B complex to be active for microtubule binding, as an inactive form in immature oocytes was also observed to bind to microtubules. The coprecipitation of suc1-column purified p34cdc2/cyclin B with purified porcine brain microtubules in the presence of starfish oocyte microtubule-associated proteins (MAPs) indicates that the association of p34cdc2/cyclin B with microtubules in vitro is mediated by MAPs.

Chapter 9 Confocal Immunofluorescence Microscopy of Microtubules in Oocytes, Eggs, and Embryos of Algae and Amphibians

Publisher Summary This chapter discusses the experiences of using immunofluorescence combined with confocal laser-scanning microscopy (CLSM) to examine cytoskeletal organization in algal and amphibian oocytes, eggs, and early embryos. Preparation of Pelvetia or Xenopus eggs for immunofluorescence microscopy follows the same procedure as is used for more typical samples, such as cultured cells grown on coverslips. Many factors enter into the design or choice of a fixation protocol for immunofluorescence. However, two factors are of paramount importance—namely, (1) the fixation protocol must be compatible with the antibodies or staining technique to be used and (2) the fixation procedure must adequately immobilize and preserve the antigen under study and the cellular structures with which it is associated. Heavy deposits of pigment in the cortex and cytoplasm of amphibian oocytes and eggs hamper immunofluorescence microscopy of these cells. Dent and Klymkowsky (1989) demonstrated that a solution of hydrogen peroxide in methanol could be used to bleach Xenopus eggs, eliminating the interfering pigment. Extended bleaching of Xenopus oocytes (up to 72 hr) does not appear to affect either the structural preservation or reactivity of microtubules with tubulin antibodies. Autofluorescence resulting from the use of glutaraldehyde-containing fixatives can be minimized by treating cells with sodium borohydride prior to incubating with antibodies.

Centrosome phosphorylation and the developmental expression of meiotic competence in mouse oocytes

Previous studies suggested that the transition from an incompetent to a competent meiotic state during the course of oogenesis in the mouse involved a G 2 M - like cell cycle transition (Wickramasinghe et al., 1991. Dev. Biol. 143, 162). The present studies tested the hypothesis that centrosome phosphorylation, an event normally induced by MPF, is required for this developmental transition and the expression of meiotic competence in cultured growing mouse oocytes. Multiple fluorescence labeling techniques were used to evaluate centrosome number, phosphorylation status, and microtubule nucleating capacity in competent and incompetent oocytes. Experimental conditions were established for reversibly altering the phosphorylation status of the centrosomes and the effects of these treatments on meiotic resumption were examined. Phosphorylated centrosomes nucleating short microtubules were observed in competent oocytes, whereas nonphosphorylated centrosomes and interphase microtubule arrays were found in incompetent oocytes. Upon recovery from nocodazole-induced microtubule depolymerization, short microtubules formed from centrosomes in competent oocytes, whereas long microtubules reappear in the cytoplasm of incompetent oocytes. Perturbation of the phosphorylation state of oocytes with activators of protein kinase A or protein kinase C resulted in the formation of long interphase microtubules in competent oocytes while centrosome phosphorylation was maintained. Treatment of competent oocytes with the phosphorylation inhibitor 6-dimethylaminopurine also led to formation of long microtubules, although under these conditions centrosomes were dephosphorylated. When competent oocytes were treated simultaneously with puromycin and the phosphodiesterase inhibitor isobutyl methylxanthine (IBMX) for 6 hr, centrosomes became dephosphorylated; centrosomes were rephosphorylated when competent oocytes were further cultured in IBMX without puromycin. Conditions that induced centrosome dephosphorylation in competent oocytes resulted in the loss of the ability to express meiotic competence in culture, whereas maintenance of centrosome phosophorylation in these oocytes was correlated with the ability to resume meiosis. These results suggest that the G 2 M transition that occurs when mouse oocytes progress from an incompetent to a competent state in vivo involves the phosphorylation of centrosomes and that the maintenance of centrosome phosphorylation is required for the in vitro expression of meiotic competence.

Organization, nucleation, and acetylation of microtubules in Xenopus laevis oocytes: A study by confocal immunofluorescence microscopy

Anti-tubulin immunofluorescence and laser-scanning confocal microscopy were used to examine microtubule organization during Xenopus oogenesis (Dumont stages I–VI). Stage I oocytes contained a poorly ordered microtubule array, characterized by concentrations of microtubules in the cortex, surrounding the germinal vesicle, and associated with the mitochondrial mass. No focus of microtubule organization was detectable by optical sectioning or in microtubule regrowth experiments, suggesting that stage I oocytes lack a functional MTOC. The microtubule array becomes progressively more complex and polarized during oogenesis; an extensive array of microtubules and microtubule bundles was apparent in the animal hemisphere of stage VI oocytes, and a less ordered array was observed in the vegetal hemisphere. A dense network of microtubules surrounded the germinal vesicle, apparently extending from a tubulin- and microtubule-rich region of cytoplasm adjacent to the vegetal surface of the GV. The organization of microtubules in normal oocytes, in oocytes recovering from cold-induced microtubule depolymerization, and in enucleated oocytes, suggested that the germinal vesicle serves as an MTOC in stage VI oocytes. Antibodies to acetylated α-tubulin revealed numerous acetylated, presumably stable, microtubules in stage I and stage VI oocytes. The array of oocyte microtubules thus might function as a stable framework for the localization of developmentally important molecules and organelles during oogenesis.

A 70 kD microtubule‐binding protein from starfish eggs: Purification, characterization, and localization during meiosis and mitosis

AbstractA microtubule‐binding protein was purified from eggs of the starfish, Asterias amurensis, through several steps of purification including the taxol‐dependent procedure [Vallee, 1982, J. Cell Biol. 92:435–442]. This protein consists of a single polypeptide chain having an apparent molecular mass of 70 kD determined by SDS‐PAGE. The 70 kD protein was identified as a unique microtubulebinding protein, judging from electrophoretic mobility, cleavage pattern by limited proteolysis, heat stability, and immunocrossreactivity. The 70 kD protein binds to brain and egg microtubules. It does not promote assembly of brain tubulin, but promotes that of egg tubulin in vitro in a concentration‐dependent manner.Using indirect immunofluorescence and immunoelectron microscopy with the anti‐70 kD protein antibody, we analyzed the cellular localization of the 70 kD protein in starfish oocytes and eggs during both meiotic maturation (meicsis) and first cleavage (mitosis). Immunofluorescence studies showed that the 70 kD protein localized on microtubule structures spread widely throughout the cytoplasm, the sperm aster, and the microtubules making up the mitotic apparatus through both meiosis and mitosis. The antibody, however, did not recognize sperm axonemes. These results were confirmed by immunoelectron microscopy. Using a colloidal gold technique, the 70 kD protein was localized along the microtubules in vivo.This 70 kD protein is the first microtubule‐binding protein that has been shown to localize along the microtubules in oocytes and eggs throughout meiosis and mitosis and to promote microtubule assembly. The 70 kD protein may be involved in the dynamic changes of microtubule structures occurring within oocytes and eggs.

Post-translational modifications of tubulin and the dynamics of microtubules in mouse oocytes and zygotes

The distribution of post-translationally modified forms of tubulin has been studied in mouse oocytes arrested in meiotic metaphase II and in interphase eggs after fertilisation. Tyrosinated and acetylated microtubules are present in the meiotic spindle but detyrosinated ones are not. Acetylation only occurs in the most stable subpopulation of microtubules in the spindles (“pole to kinetochore”). After fertilisation, many microtubules of the interphase array become acetylated, but detyrosination occurs only at a very low level.

Microtubules in mouse oocytes, zygotes, and embryos during fertilization and early development: unusual configurations and arrest of mammalian fertilization with microtubule inhibitors.

Annals of the New York Academy of SciencesVolume 466, Issue 1 p. 945-948 Microtubules in Mouse Oocytes, Zygotes, and Embryos during Fertilization and Early Development: Unusual Configurations and Arrest of Mammalian Fertilization with Microtubule Inhibitorsa GERALD SCHATTEN, GERALD SCHATTEN Department of Biological Science Florida State University Tallahassee, Florida 32306Search for more papers by this authorCALVIN SIMERLY, CALVIN SIMERLY Department of Biological Science Florida State University Tallahassee, Florida 32306Search for more papers by this authorHEIDE SCHATTEN, HEIDE SCHATTEN Department of Biological Science Florida State University Tallahassee, Florida 32306Search for more papers by this author GERALD SCHATTEN, GERALD SCHATTEN Department of Biological Science Florida State University Tallahassee, Florida 32306Search for more papers by this authorCALVIN SIMERLY, CALVIN SIMERLY Department of Biological Science Florida State University Tallahassee, Florida 32306Search for more papers by this authorHEIDE SCHATTEN, HEIDE SCHATTEN Department of Biological Science Florida State University Tallahassee, Florida 32306Search for more papers by this author First published: June 1986 https://doi.org/10.1111/j.1749-6632.1986.tb38481.xCitations: 8 a Support of this research by the National Institutes of Health and the National Science Foundation is gratefully acknowledged. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume466, Issue1Dynamic Aspects of Microtubule BiologyJune 1986Pages 945-948 RelatedInformation

Cyclic assembly-disassembly of cortical microtubules during maturation and early development of starfish oocytes

An extensive array of cortical microtubules in oocytes of the starfish Pisaster ochraceus undergoes multiple cycles of disappearance and reapparance during maturation and early development. These events were studied in isolated fragments of the oocyte cortex stained with antitubulin antibodies for indirect immunofluorescence. The meshwork of long microtubules is present in the cortex (a) of immature oocytes, i.e., before treatment with the maturation-inducing hormone 1-methyladenine, (b) for 10–20 min after treatment with 1-methyladenine, (c) after formation of the second polar body (in reduced numbers in unfertilized oocytes), and (d) in the intermitotic period between first and second cleavage divisions. The array of cortical microtubules is absent in oocytes (a) undergoing germinal vesicle breakdown, (b) during the two meiotic divisions (polar body divisions), and (c) during mitosis of the first and, perhaps, subsequent cleavage divisions. The cycle of assembly-disassembly of cortical microtubules is synchronized to the cycle of nuclear envelope breakdown and reformation and to the mitotic cycle; specifically, cortical microtubules are present when a nucleus is intact (germinal vesicle, female pronucleus, zygote nucleus, blastomere nucleus) and are absent whenever a meiotic or mitotic spindle is present. These findings are discussed in terms of microtubule organizing centers in eggs, possible triggers for microtubule assembly and disassembly, the eccentric location of the germinal vesicle, and the regulation of oocyte maturation and cell division.