Laser scanning confocal microscopic analysis of cytoskeletal and nuclear reorganization in live Drosophila embryos

1993 ◽  
Vol 51 ◽  
pp. 174-175
Author(s):  
William Theurkauf
Keyword(s):  
Laser Scanning ◽  
Microscopic Analysis ◽  
Large Cell ◽  
Early Embryo ◽  
Drosophila Embryo ◽  
Cortical Actin ◽  
Nuclear Reorganization ◽  
Cytoskeletal Elements ◽  
Microtubule Structure ◽  
Drosophila Embryos

Cell division in eucaryotes depends on coordinated changes in nuclear and cytoskeletal components. In Drosophila melanogaster embryos, the first 13 nuclear divisions occur without cytokinesis. During the final four divisions, nuclei divide in a uniform monolayer at the surface of the embryo. These surface divisions are accompanied by dramatic changes in cortical actin and microtubule structure (Karr and Alberts, 1986), and inhibitor studies indicate that these changes are essential to orderly mitosis (Zalokar and Erk, 1976). Because the early embryo is syncytial, fluorescent probes introduced by microinjection are incorporated in structures associated with all of the nuclei in the blastoderm. In addition, the nuclei divide synchronously every 10 to 20 min. These characteristics make the syncytial blastoderm embryo an excellent system for the analysis of mitotic reorganization of both nuclear and cytoskeletal elements. However, the Drosophila embryo is a large cell, and resolution of cytoskeletal filaments and nuclear structure is hampered by out-of focus signal.

Arrest of intravitelline mitoses in Drosophila embryos by u.v. irradiation of the egg surface

Development ◽  
1984 ◽  
Vol 80 (1) ◽  
pp. 43-61
Author(s):  
Shin Togashi ◽  
Masukichi Okada
Keyword(s):  
Cell Cycle ◽  
Single Cell ◽  
Control Mechanism ◽  
Drosophila Embryo ◽  
Posterior Half ◽  
Simple Diffusion ◽  
Cytoplasmic Region ◽  
Anterior Half ◽  
Cytoskeletal Elements ◽  
Drosophila Embryos

The intravitelline mitosis in Drosophila was arrested at the anaphase within the span of a single cell cycle after irradiation with 300 nm u.v. Embryos at and before the 8-nucleus stage were influenced by the u.v. only when irradiated anteriorly, while at and after the 16-nucleus stage, embryos are sensitive to either anterior or posterior irradiation. In embryos anteriorly irradiated at or before the 8-nucleus stage all nuclei in the embryo were prevented from performing mitosis. When irradiated at or after the 16-nucleus stage, inhibition of the intravitelline mitosis is limited to the nuclei in approximately anterior-half region of embryos in anterior irradiation, and to those inapproximately posterior-half region in posterior irradiation, resulting in incomplete blastoderm formation. Sites sensitive to 300 nm u.v. are postulated to be present in the peripheral cytoplasmic region of the embryo and not in the nucleus, because the half-attenuation thickness of 300 nm u.v. light for the Drosophila egg cytoplasm is 3 µm and nuclei are at least 50 µm away from the periphery at the stage of irradiation. In addition lateral irradiation of a portion of an egg where there is no nucleus underneath was also effective in arresting division of nuclei in the same egg. It is suggested that the effects of 300nm u.v. may not be conveyed to the nuclei from the periphery by simple diffusion of a substance, and a hypothesis is proposed for the involvement of cytoskeletal elements associated with the u.v. sensitive sites on the surface to the control mechanism of the intravitelline mitosis of the Drosophila embryo.

F-actin organization during the cellularization of the Drosophila embryo as revealed with a confocal laser scanning microscope

1990 ◽  
Vol 96 (1) ◽  
pp. 35-42
Author(s):  
R.M. Warn ◽  
M. Robert-Nicoud
Keyword(s):  
Laser Scanning ◽  
Confocal Laser Scanning Microscope ◽  
Confocal Laser Scanning ◽  
Drosophila Embryo ◽  
Confocal Laser ◽  
Actin Network ◽  
Scanning Microscope ◽  
Cortical Actin ◽  
Laser Scanning Microscope ◽  
Actin Organization

The changes in F-actin organization during the cellularization of the Drosophila embryo have been studied with a confocal laser scanning microscope using fluorescein-phalloidin as a specific stain. Particular study has been made of the changes in the organization of the F-actin network associated with the leading edges of the growing membranes. The role of this actin network in the cellularization process is considered. Other actin-containing structures have also been examined, including the cortical actin layer and a conspicuous region of F-actin aggregates, present beneath the level of the forming cell membranes.

scholarly journals MATERNAL-ZYGOTIC GENE INTERACTIONS DURING FORMATION OF THE DORSOVENTRAL PATTERN IN DROSOPHILA EMBRYOS

Genetics ◽  
1983 ◽  
Vol 105 (3) ◽  
pp. 615-632 ◽  
Author(s):  
Pat Simpson
Keyword(s):  
Early Embryo ◽  
Drosophila Embryo ◽  
Sensitive Period ◽  
Temperature Sensitive ◽  
Mutant Genotype ◽  
Dominant Phenotype ◽  
Zygotic Gene ◽  
Definition Of ◽  
Mutant Phenotypes ◽  
Dominant Lethality

ABSTRACT Maternal-zygotic interactions involving the three genes dorsal (dl), twist (twi) and snail (sna) are described. The results suggest that all three are involved in the process by which the dorsoventral pattern of the Drosophila embryo is established. First, the lethal embryonic mutant phenotypes are rather similar. In homozygous twi or sna embryos invagination of the ventral presumptive mesodermal cells fails to occur, and the resulting embryos are devoid of internal organs. This is very similar to the dominant phenotype described for dl; in the case of dl, however, the effect is a maternal one dependent on the mutant genotype of the female. Second, a synergistic interaction has been found whereby dominant lethality of twi  - or sna-bearing zygotes is observed in embryos derived from heterozygous dl females at high temperature. The temperature sensitivity of this interaction permitted definition of a temperature-sensitive period which is probably that of dl. This was found to extend from approximately 12 hr prior to oviposition to 2— 3 hr of embryogenesis. A zygotic action for the dl gene in addition to the maternal effect was revealed by the finding that extra doses of dl  + in the zygotes can partially rescue the dominant lethality of heterozygous twi embryos derived from heterozygous dl females. Two possible interpretations of the synergism are considered: (1) twi and sna are activated in the embryos as a result of positional signals placed in the egg as a consequence of the functioning of the dl gene during oogenesis and, thus, play a role in embryonic determination. (2) The gene products of dl  + and twi  + (or sna  +) combine to produce a functional molecule that is involved in the specification of dorsoventral pattern in the early embryo.

Confocal laser scanning microscopic analysis of the penetration of an epoxy resin‐based sealer into dentinal tubules after calcium hydroxide dressing

2021 ◽  
Author(s):  
Manoel E.L. Machado ◽  
Virginia Natalia Veintimilla Lozada ◽  
Karol Jasmin Carrillo Rengifo ◽  
Raquel E.G. Guillén ◽  
Hector Caballero‐Flores ◽  
...  
Keyword(s):  
Epoxy Resin ◽  
Calcium Hydroxide ◽  
Laser Scanning ◽  
Microscopic Analysis ◽  
Confocal Laser Scanning ◽  
Confocal Laser ◽  
Dentinal Tubules

scholarly journals Specific release of membrane-bound annexin II and cortical cytoskeletal elements by sequestration of membrane cholesterol.

1997 ◽  
Vol 8 (3) ◽  
pp. 533-545 ◽  
Author(s):  
T Harder ◽  
R Kellner ◽  
R G Parton ◽  
J Gruenberg
Keyword(s):  
Actin Cytoskeleton ◽  
Cytoskeletal Proteins ◽  
Annexin Ii ◽  
Dependent Manner ◽  
Cortical Actin ◽  
Independent Manner ◽  
Low Concentrations ◽  
Early Endosomes ◽  
Associated Proteins ◽  
Cytoskeletal Elements

Annexin II is an abundant protein which is present in the cytosol and on the cytoplasmic face of plasma membrane and early endosomes. It is generally believed that this association occurs via Ca(2+)-dependent binding to lipids, a mechanism typical for the annexin protein family. Although previous studies have shown that annexin II is involved in early endosome dynamics and organization, the precise biological role of the protein is unknown. In this study, we found that approximately 50% of the total cellular annexin was associated with membranes in a Ca(2+)-independent manner. This binding was extremely tight, since it resisted high salt and, to some extent, high pH treatments. We found, however, that membrane-associated annexin II could be quantitatively released by low concentrations of the cholesterol-sequestering agents filipin and digitonin. Both treatments released an identical and limited set of proteins but had no effects on other membrane-associated proteins. Among the released proteins, we identified, in addition to annexin II itself, the cortical cytoskeletal proteins alpha-actinin, ezrin and moesin, and membrane-associated actin. Our biochemical and immunological observations indicate that these proteins are part of a complex containing annexin II and that stability of the complex is sensitive to cholesterol sequestering agents. Since annexin II is tightly membrane-associated in a cholesterol-dependent manner, and since it seems to interact physically with elements of the cortical actin cytoskeleton, we propose that the protein serves as interface between membranes containing high amounts of cholesterol and the actin cytoskeleton.

An activity gradient of decapentaplegic is necessary for the specification of dorsal pattern elements in the Drosophila embryo

Development ◽  
1993 ◽  
Vol 117 (2) ◽  
pp. 807-822 ◽  
Author(s):  
K.A. Wharton ◽  
R.P. Ray ◽  
W.M. Gelbart
Keyword(s):  
Cell Fate ◽  
Gene Dosage ◽  
Early Embryo ◽  
Drosophila Embryo ◽  
Cell Fates ◽  
Gene Encoding ◽  
In The Wild ◽  
Intercellular Signalling ◽  
Overlapping Domains ◽  
Dorsal Pattern

decapentaplegic (dpp) is a zygotically expressed gene encoding a TGF-beta-related ligand that is necessary for dorsal-ventral patterning in the Drosophila embryo. We show here that dpp is an integral part of a gradient that specifies many different cell fates via intercellular signalling. There is a graded requirement for dpp activity in the early embryo: high levels of dpp activity specify the amnioserosa, while progressively lower levels specify dorsal and lateral ectoderm. This potential for dpp to specify cell fate is highly dosage sensitive. In the wild-type embryo, increasing the gene dosage of dpp can shift cell fates along the dorsal-ventral axis. Furthermore, in mutant embryos, in which only a subset of the dorsal-ventral pattern elements are represented, increasing the gene dosage of dpp can specifically transform those pattern elements into more dorsal ones. We present evidence that the zygotic dpp gradient and the maternal dorsal gradient specify distinct, non-overlapping domains of the dorsal-ventral pattern.

Mutations affecting the cytoskeletal organization of syncytial Drosophila embryos

Development ◽  
1993 ◽  
Vol 118 (4) ◽  
pp. 1245-1254 ◽  
Author(s):  
W. Sullivan ◽  
P. Fogarty ◽  
W. Theurkauf
Keyword(s):  
Mitotic Division ◽  
P Element ◽  
Drosophila Embryo ◽  
Nuclear Movement ◽  
Microtubule Organization ◽  
Cytoskeletal Organization ◽  
New Genes ◽  
Movement Organization ◽  
Cytoplasmic Organization ◽  
Drosophila Embryos

Cytoplasmic organization, nuclear migration, and nuclear division in the early syncytial Drosophila embryo are all modulated by the cytoskeleton. In an attempt to identify genes involved in cytoskeletal functions, we have examined a collection of maternal-effect lethal mutations induced by single P-element transposition for those that cause defects in nuclear movement, organization, or morphology during the syncytial embryonic divisions. We describe three mutations, grapes, scrambled, and nuclear-fallout, which define three previously uncharacterized genes. Females homozygous for these mutations produce embryos that exhibit extensive mitotic division errors only after the nuclei migrate to the surface. Analysis of the microfilament and microtubule organization in embryos derived from these newly identified mutations reveal disruptions in the cortical cytoskeleton. Each of the three mutations disrupts the actin-based pseudocleavage furrows and the cellularization furrows in a distinct fashion. In addition to identifying new genes involved in cytoskeletal organization, these mutations provide insights into cytoskeletal function during early Drosophila embryogenesis.

scholarly journals Dia- and Rok-dependent enrichment of capping proteins in a cortical region

2021 ◽  
Author(s):  
Anja Schmidt ◽  
Long Li ◽  
Zhiyi Lv ◽  
Shuling Yan ◽  
Jörg Großhans
Keyword(s):  
Myosin Ii ◽  
Rho Kinase ◽  
Cortical Region ◽  
Protein Enrichment ◽  
Cortical Actin ◽  
Capping Protein ◽  
Capping Proteins ◽  
Muscle Myosin ◽  
Drosophila Embryos

Rho signaling with its major targets the formin Dia, Rho kinase (Rok) and non-muscle myosin II control turnover, amount and contractility of actomyosin. Much less investigated has been a potential function for the distribution of F-actin plus and minus ends. In syncytial Drosophila embryos Rho1 signaling is high between actin caps, i. e. the cortical intercap region. Capping protein binds to free plus ends of F-actin to prevent elongation of the filament. Capping protein has served as a marker to visualize the distribution of F-actin plus ends in cells and in vitro. Here, we probed the distribution of plus ends with capping protein in syncytial Drosophila embryos. We found that Capping proteins are specifically enriched in the intercap region similar to Dia and MyoII but distinct from overall F-actin. The intercap enrichment of Capping protein was impaired in dia mutants and embryos, in which Rok and MyoII activation was inhibited. Our observations reveal that Dia and Rok/MyoII control Capping protein enrichment and support a model that Dia and Rok/MyoII control the organization of cortical actin cytoskeleton downstream of Rho1 signaling.

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