共查询到20条相似文献,搜索用时 46 毫秒
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The early embryonic divisions of Drosophila melanogaster are characterized by rapid, synchronized changes of the nuclei and surrounding cytoskeleton. We report evidence that these changes are carried out by two separately organized systems. DNA was sufficient to cause assembly of nuclear lamina and the formation of nuclear membrane with pore structures. Free centrosomes were correlated with the formation of microtubule, microfilament and spectrin networks in the absence of nuclei. In addition, we found that the morphology of the cytoskeleton associated with the free centrosomes cycled in response to the embryonic cell cycle cues. These observations suggest that the centrosomes may be responsible for the organization of this extensive cytoskeleton. The early divisions may therefore result from the independent cycling of two systems, the nucleus and the surrounding cytoskeleton, that respond separately to the mitotic cues in the embryo and function together to give the synchronized early divisions. The Drosophila embryo has an "intermediate" mitotic system in which the nuclear membrane does not break down completely during mitosis. We speculate that the principles of cytoskeleton organization in this system may be different from those of the Xenopus "open" mitotic system. 相似文献
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An injection of aphidicolin into early Drosophila embryos inhibits DNA synthesis and nuclear division, while centrosome replication and many other aspects of the mitotic cycle continue. If aphidicolin is injected at nuclear cycle 7-8, the normal migration of nuclei to the embryo cortex is completely inhibited. In most of these embryos, however, centrosomes continue to migrate in a coordinated manner to the cortex, where they reorganize tubulin, actin, and the overlying plasma membrane. Remarkably, the centrosomes that migrate to the posterior pole of such embryos initiate pole cell formation in the absence of nuclei. These observations demonstrate that centrosomes alone are able to direct a major reorganization of the cortical cytoskeleton when they arrive at the surface of the embryo. They also suggest that the coordinated movement of nuclei to the embryo cortex is mediated by forces acting on the centrosome rather than on the nucleus itself. 相似文献
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Hester P.M. Pratt 《Developmental biology》1982,89(1):101-110
The total cholesterol content of preimplantation mouse embryos increases approximately threefold (to 1 pmole) during the development of a blastocyst from a fertilized egg. From the two-cell stage onwards embryos are capable of converting [3H]mevalonate into the membrane sterols lanosterol and cholesterol. However, activity of the ratelimiting enzyme in sterol synthesis, hydroxymethylglutaryl coenzyme A reductase, was only measurable in late expanded blastocysts. These estimates of cholesterol content and the amounts of 3H-sterol formed suggest that the preimplantation mouse embryo can synthesize membrane sterols from early cleavage stages onwards. Late compaction and early fluid accumulation (approx. 84 hr post-hCG) are associated with a transition from lanosterol to cholesterol synthesis. The possible relationship between this transition and changes in the properties of embryo membranes which occur at this time is discussed. The results, taken together with previous evidence for phospholipid synthesis in early embryos, demonstrate that the preimplantation mouse embryo is capable of synthesizing major membrane lipids and hence has the potential for assembling cell membranes and modulating their lipid-mediated properties. 相似文献
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We have used two different experimental approaches to demonstrate topological separation of parental genomes in preimplantation mouse embryos: mouse eggs fertilized with 5-bromodeoxyuridine (BrdU)-labeled sperm followed by detection of BrdU in early diploid embryos, and differential heterochromatin staining in mouse interspecific hybrid embryos. Separation of chromatin according to parental origin was preserved up to the four-cell embryo stage and then gradually disappeared. In F1 hybrid animals, genome separation was also observed in a proportion of somatic cells. Separate nuclear compartments during preimplantation development, when extreme chromatin remodelling occurs, and possibly in some differentiated cell types, may be associated with epigenetic reprogramming. 相似文献
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A J Watson K E Wiemer M Arcellana-Panlilio G A Schultz 《Molecular reproduction and development》1992,31(4):231-240
This study describes the localization of the U2 small nuclear RNA (snRNA) and the major U snRNA group ribonucleoproteins (snRNPs) during bovine preimplantation development. In vitro maturation, fertilization, and oviductal epithelial cell coculture methods were employed to produce several developmental series totalling over 2,000 preimplantation-stage bovine oocytes and embryos. These oocytes and preimplantation embryos were processed for in situ hybridization, immunofluorescence and Northern blotting methods. The U2 snRNA and the major U group snRNPS were localized initially over the germinal vesicle (GV) of preovulatory oocytes but following GV breakdown were released throughout the ooplasm. They subsequently reassociated with both pronuclei during fertilization. From the two-cell to the blastocyst stages, the U2 snRNA and U snRNPs were localized to the interphase nucleus of each blastomere. The levels of U2 snRNA throughout bovine preimplantation development were determined by probing a Northern blot containing total RNA isolated from the following preimplantation bovine embryo stages: one to two cell, eight to 16 cell, early morula (greater than 32 cell), and late morula/early blastocysts. The levels of U2 snRNA remained constant between the one-cell and eight- to 16-cell bovine embryo stages but increased 4.4-fold between the eight- to 16-cell stage and the late morula/early blastocyst stages. The results suggest that a maternal pool of snRNAs is maintained in mammalian preimplantation embryos regardless of the duration of maternal control of development. 相似文献
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Wang QT Piotrowska K Ciemerych MA Milenkovic L Scott MP Davis RW Zernicka-Goetz M 《Developmental cell》2004,6(1):133-144
The preimplantation development of the mammalian embryo encompasses a series of critical events: the transition from oocyte to embryo, the first cell divisions, the establishment of cellular contacts, the first lineage differentiation-all the first subtle steps toward a future body plan. Here, we use microarrays to explore gene activity during preimplantation development. We reveal robust and dynamic patterns of stage-specific gene activity that fall into two major phases, one up to the 2-cell stage (oocyte-to-embryo transition) and one after the 4-cell stage (cellular differentiation). The mouse oocyte and early embryo express components of multiple signaling pathways including those downstream of Wnt, BMP, and Notch, indicating that conserved regulators of cell fate and pattern formation are likely to function at the earliest embryonic stages. Overall, these data provide a detailed temporal profile of gene expression that reveals the richness of signaling processes in early mammalian development. 相似文献
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Wei Y Multi S Yang CR Ma J Zhang QH Wang ZB Li M Wei L Ge ZJ Zhang CH Ouyang YC Hou Y Schatten H Sun QY 《PloS one》2011,6(6):e21557
Errors in chromosome segregation or distribution may result in aneuploid embryo formation, which causes implantation failure, spontaneous abortion, genetic diseases, or embryo death. Embryonic aneuploidy occurs when chromosome aberrations are present in gametes or early embryos. To date, it is still unclear whether the spindle assembly checkpoint (SAC) is required for the regulation of mitotic cell cycle progression to ensure mitotic fidelity during preimplantation development. In this study, using overexpression and RNA interference (RNAi) approaches, we analyzed the role of SAC components (Bub3, BubR1 and Mad2) in mouse preimplantation embryos. Our data showed that overexpressed SAC components inhibited metaphase-anaphase transition by preventing sister chromatid segregation. Deletion of SAC components by RNAi accelerated the metaphase-anaphase transition during the first cleavage and caused micronuclei formation, chromosome misalignment and aneuploidy, which caused decreased implantation and delayed development. Furthermore, in the presence of the spindle-depolymerizing drug nocodazole, SAC depleted embryos failed to arrest at metaphase. Our results suggest that SAC is essential for the regulation of mitotic cell cycle progression in cleavage stage mouse embryos. 相似文献
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Somatic cell-like features of cloned mouse embryos prepared with cultured myoblast nuclei 总被引:5,自引:0,他引:5
Cloning by somatic cell nuclear transfer requires silencing of the donor cell gene expression program and the initiation of the embryonic gene expression program (nuclear reprogramming). Failure to silence the donor cell program could lead to altered embryonic phenotypes. Cloned mouse embryos produced using myoblast nuclei fail to thrive in standard embryo culture media but flourish in somatic cell culture media favored by the donor myoblasts themselves, forming blastocysts at a significant rate, with robust morphologies, high total cell number, and a normal allocation of cells to the inner cell mass in most embryos. Myoblast cloned embryos continue expressing the GLUT4 glucose transporter, which is typically expressed in muscle but not in preimplantation stage embryos. Myoblast clones also exhibit precocious enrichment of GLUT1 at the cell surface. Both myoblast and cumulus cell cloned embryos exhibit enhanced rates of glucose uptake. These observations indicate that silencing of the donor cell genome during cloning either is incomplete or occurs progressively over the course of preimplantation development. As a result, cloned embryos initially exhibit many somatic cell-like characteristics. Tetraploid constructs, which possess a transplanted somatic cell genome plus the oocyte-derived chromosomes, exhibit a more embryonic-like pattern of gene expression and culture preference. We conclude that preimplantation stage cloned embryos have profoundly altered characteristics that are donor cell type specific and that exposure of cloned embryos to standard embryo culture conditions may lead to disruptions in basic homeostasis and inhibition of a range of essential processes including further nuclear reprogramming, contributing to cloned embryo demise. 相似文献
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In nondomestic and endangered species, the use of domestic animal oocytes as recipients for exotic donor nuclei causes the normal pattern of cytoplasmic inheritance to be disrupted, resulting in the production of nuclear-cytoplasmic hybrids. Evidence suggests that conflict between nuclear and cytoplasmic control elements leads to a disruption of normal cellular processes, including metabolic function and cell division. This study investigated the effects of nuclear-cytoplasmic interactions on the developmental potential of interspecies embryos produced by in vitro fertilization and somatic cell nuclear transfer: cattle x cattle, gaur x cattle, hybrid x cattle. Cattle control and hybrid embryos were examined for development to the blastocyst stage and blastocyst quality, as determined by cell number and allocation, apoptosis incidence, and expression patterns of mitochondria-related genes. These analyses demonstrated that a 100% gaur nucleus within a domestic cattle cytoplasmic environment was not properly capable of directing embryo development in the later preimplantation stages. Poor blastocyst development accompanied by developmental delay, decreased cell numbers, and aberrant apoptotic and related gene expression profiles, all signs of disrupted cellular processes associated with mitochondrial function, were observed. Developmental potential was improved when at least a portion of the nuclear genome corresponded to the inherited cytoplasm, indicating that recognition of cytoplasmic components by the nucleus is crucial for proper cellular function and embryo development. A better understanding of the influence of the cytoplasmic environment on embryonic processes is necessary before interspecies somatic cell nuclear transfer can be considered a viable alternative for endangered species conservation. 相似文献
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Expression of Wnt genes during mouse preimplantation development 总被引:2,自引:0,他引:2
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The intracellular trafficking of integral membrane and secreted proteins is likely to be a key element involved in the morphogenesis
and differentiation of the early mammalian embryo. In this study, we used transmission electron microscopy (TEM) to analyse
the effects of brefeldin-A (BFA) and monensin, well known inhibitors of vesicular protein trafficking in somatic cells, on
the structure of preimplantation mouse embryos. Both BFA and monensin distinctively altered the morphology of Golgi compartments
in the blastomeres of treated morulae. BFA-treated morulae lacked recognizable Golgi complexes but possessed heterogeneous
organelle clusters consisting of an abundance of smooth tubular and vesicular membrane compartments in addition to mitochondria,
endosomes and lysosomes. Treatment of morulae with monensin was associated with swelling of Golgi compartments in addition
to altering the morphology of mitochondria, lysosomes and the plasma membrane. BFA, and to a lesser extent monensin, inhibited
cytokinesis as evidenced by the detection of binucleate blastomeres. In addition, BFA induced morulae to decompact. These
latter effects have not been reported previously for these agents in mammalian somatic cell lines or other vertebrate or invertebrate
embryos. These results provide the first demonstration of the structural effects of BFA and monensin on cells of the early
mammalian embryo, some of which are consistent with the known actions of these agents on components of the vesicular protein
trafficking system in mammalian somatic cells. This information serves as a foundation for the further use of these agents
in studies of vesicular protein trafficking as an agent of preimplantation morphogenesis.
Received: 22 April 1996 / Accepted: 4 December 1996 相似文献
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Calle A Fernandez-Gonzalez R Ramos-Ibeas P Laguna-Barraza R Perez-Cerezales S Bermejo-Alvarez P Ramirez MA Gutierrez-Adan A 《Theriogenology》2012,77(4):785-793
The mouse is a convenient model to analyze the impact of in vitro culture (IVC) on the long-term health and physiology of the offspring, and the possible inheritance of these altered phenotypes. The preimplantation period of mammalian development has been identified as an early ‘developmental window’ during which environmental conditions may influence the pattern of future growth and physiology. Suboptimal culture media can cause severe alterations in mRNA expression in the embryo, which are associated with embryo quality reduction. In addition, the embryonic epigenetic reprogramming may also be severely affected by IVC, modifying epigenetic marks particularly in imprinted genes and epigenetically sensitive alleles. These altered epigenetic marks can persist after birth, resulting in adult health problems such as obesity, increased anxiety and memory deficits. Furthermore, some epigenetic modifications have been found to be transmitted to the offspring (epigenetic transgenerational inheritance), thereby providing a suitable model to asses risks of cross-generational effects of perturbing early embryo development. This review will highlight how preimplantation environment changes can not only affect developmental processes taking place at that time, but can also have an impact further, affecting offspring health and physiology; and how they may be transmitted to the next generation. We will also analyze the emerging role of epigenetics as a mechanistic link between the early environment and the later phenotype of the developing organism. 相似文献