Three-Dimensional reconstruction of the synaptonemal complex from pachytene maize meiocytes using Electron Microscopy tomography

1993 ◽  
Vol 51 ◽  
pp. 182-183
Author(s):  
Jennifer C. Fung ◽  
Bethe A. Scalettar ◽  
David A. Agard ◽  
John W. Sedat
Keyword(s):  
Electron Microscopy ◽  
Synaptonemal Complex ◽  
Chromosome Segregation ◽  
Three Dimensional ◽  
Central Element ◽  
Amorphous Structure ◽  
Two Dimensional ◽  
Homologous Chromosomes ◽  
Exact Function ◽  
Dimensional Reconstruction

The synaptonemal complex (SC) is a structure involved in the synapsis of homologous chromosomes during the prophase I stage of meiosis. Although the exact function of the complex is unknown, it has been suggested that one possible role might be to promote recombination by ensuring close synapsis of the homologous chromosomes. In addition, it is thought that the SC may also be required to convert the resulting recombination events into functional chiasmata to provide for proper chromosome segregation at the end of the first stage of meiosis.The SC structure itself is highly conserved across a variety of species. The organization of the SC is tripartite consisting of lateral, central and transverse elements. Two-dimensional cytological observations have been made to characterize the general features of these SC components. The lateral elements are 300 - 500 Å wide proteinaceous structures which flank the synapsed regions of the chromosome bivalent. Between the two lateral elements is a central region containing the central element commonly characterized as a less dense amorphous structure.

Three-Dimensional reconstruction of the synaptonemal complex from high-pressure frozen maize meiocytes using IVEM Tomography

1994 ◽  
Vol 52 ◽  
pp. 14-15
Author(s):  
Jennifer C. Fung ◽  
David A. Agard ◽  
John W. Sedat
Keyword(s):  
Synaptonemal Complex ◽  
Three Dimensional ◽  
Central Element ◽  
Homologous Chromosomes ◽  
Macromolecular Assembly ◽  
Dimensional Reconstruction ◽  
Protein Components ◽  
Basic Features ◽  
General Architecture ◽  
Internal Architecture

The synaptonemal complex (SC) is a key macromolecular assembly formed during meiosis of most eukaryotes. It has a crucial role in maintaining synapsis between homologous chromosomes and in ensuring proper segregation of the homologs through the establishment of functional chiasmata. Recently, biochemical and genetic efforts have begun to identify some of the protein components of the SC. As these efforts progress, a more detailed analysis of SC structure will also be needed to incorporate these new components into the overall organization of the SC.Early efforts into the analysis of SC structure have established that its general architecture is conserved throughout many organisms. The basic features found in every SC are the two lateral elements and the central element, both which run longitudinally between the homologs during the pachytene stage of prophase I. Transverse elements which run perpendicular to the homolog axis through the central region are also often found. Although the general features of the SC are conserved, the internal architecture of these components can differ.

The synaptonemal complexes of Achlya recurva (Oomycetes): karyotype analysis and three-dimensional reconstruction of pachytene nuclei in antheridia and oogonia

1991 ◽  
Vol 69 (6) ◽  
pp. 1384-1395 ◽  
Author(s):  
Hobart R. Williamson ◽  
Pesach Ben Yitzchak
Keyword(s):  
Synaptonemal Complex ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolus Organizer Region ◽  
Three Dimensional ◽  
Central Element ◽  
Three Dimensional Reconstruction ◽  
Synaptonemal Complexes ◽  
Sequence Of Events ◽  
Dimensional Reconstruction

Fifteen synaptonemal complexes, as determined by three-dimensional reconstruction of serial, ultrathin sections, were present within both antheridial and oogonial zygotene and pachytene nuclei of the oomyceteous fungus Achlya recurva, thus n = 15. The present study represents the first complete reconstruction of synaptonemal complexes in the genus Achlya. The occurrence of both zygonema and pachynema was simultaneous in antheridia and oogonia. Pachytene nuclei of antheridia and oogonia are small, 13 μm3 in volume, and the average length of the synaptonemal complexes ranged from 1.9 to 4.4 μm. Lateral elements at zygotene ranged from 1.2 to 4.7 μm. Both ends of each synaptonemal complex were attached randomly to the nuclear envelope, so a bouquet formation was not observed at pachytene. In A. recurva, the dimensions of the synaptonemal complex were as follows: overall width = 270 nm; the lateral elements = 75 nm each in width and the central region = 120 nm. There was no central element and associated transverse filaments, which may be associated with development of alternative reproductive strategies other than amphimixis, as in nematodes. Of the 15 synaptonemal complexes present, only the one carrying the nucleolus organizer region could be clearly identified from one nucleus to the next. The nucleolar organizer region was on the average 0.75 μm from the telomere in both zygotene and pachytene nuclei. There were an average of three recombination nodules in each nucleus. Synaptonemal complexes have been reported in over 80 different species of fungi and related protista. Karyotypic evolution in the oomycetes and fungi may be the result of poly-ploidization, followed by cytogenetic diversification involving aneuploidy and differing degrees of polyploidy. Such a sequence of events could explain the apparent polyphyletic formation of this group. Key words: karyotype, Oomycetes, pachytene, synaptonemal complexes, three-dimensional reconstruction.

scholarly journals A close-to-native structure of the synaptonemal complex

2021 ◽  
Author(s):  
Rosario Ortiz ◽  
Olga M Echeverria ◽  
Sergej Masich ◽  
Christer Hoog ◽  
Abrahan Hernandez-Hernandez
Keyword(s):  
Electron Microscopy ◽  
Genetic Variability ◽  
Synaptonemal Complex ◽  
Central Region ◽  
Genetic Material ◽  
Central Element ◽  
Structural Models ◽  
Super Resolution ◽  
Native Structure ◽  
Homologous Chromosomes

Genetic variability in sexually reproducing organisms results from an exchange of genetic material between homologous chromosomes. The genetic exchange mechanism is dependent on the synaptonemal complex (SC), a protein structure localized between the homologous chromosomes. Current structural models of the SC are based on electron microscopy, super resolution, and expansion microscopy studies using chemical fixatives and sample dehydration of gonads, which are methodologies known to produce structural artifacts. We have developed a novel electron microscopy sample-preparation approach where pachytene cells are isolated from mouse testis by FACS, followed by cryo-fixation and cryo-substitution to achieve visualization of a close-to-native structure of the SC. We found that the central region of the SC was wider than previously recognized, and the transverse filaments more densely packed in the central region. Furthermore, we identified a structure nucleating the central element of the SC.

Three-Dimensional Electron Microscopy of Individual Biological Objects

1976 ◽  
Vol 31 (6) ◽  
pp. 645-655 ◽  
Author(s):  
W. Hoppe ◽  
H. J. Schramm ◽  
M. Sturm ◽  
N. Hunsmann ◽  
J. Gaßmann
Keyword(s):  
Electron Microscopy ◽  
Three Dimensional ◽  
Image Point ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Biological Objects ◽  
Dimensional Reconstruction ◽  
The Common ◽  
Measuring Scheme

In this paper methods and results of three-dimensional electron microscopy of individual molecules will be presented. Part I describes the general experimental and theoretical methods (microgoniometer, measuring scheme, two-dimensional and three-dimensional reconstruction, determination of the common origin of the projections). Special attention will be given to the image point shapes under different reconstruction conditions

scholarly journals Superresolution expansion microscopy reveals the three-dimensional organization of the Drosophila synaptonemal complex

2017 ◽  
Vol 114 (33) ◽  
pp. E6857-E6866 ◽  
Author(s):  
Cori K. Cahoon ◽  
Zulin Yu ◽  
Yongfu Wang ◽  
Fengli Guo ◽  
Jay R. Unruh ◽  
...  
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Segregation ◽  
Biological Sample ◽  
3D Model ◽  
Three Dimensional ◽  
Optical Resolution ◽  
Structured Illumination ◽  
Structured Illumination Microscopy ◽  
Homologous Chromosomes ◽  
Superresolution Microscopy

The synaptonemal complex (SC), a structure highly conserved from yeast to mammals, assembles between homologous chromosomes and is essential for accurate chromosome segregation at the first meiotic division. In Drosophila melanogaster, many SC components and their general positions within the complex have been dissected through a combination of genetic analyses, superresolution microscopy, and electron microscopy. Although these studies provide a 2D understanding of SC structure in Drosophila, the inability to optically resolve the minute distances between proteins in the complex has precluded its 3D characterization. A recently described technology termed expansion microscopy (ExM) uniformly increases the size of a biological sample, thereby circumventing the limits of optical resolution. By adapting the ExM protocol to render it compatible with structured illumination microscopy, we can examine the 3D organization of several known Drosophila SC components. These data provide evidence that two layers of SC are assembled. We further speculate that each SC layer may connect two nonsister chromatids, and present a 3D model of the Drosophila SC based on these findings.

Image Reconstruction Applied to High Voltage Microscopy

1974 ◽  
Vol 32 ◽  
pp. 396-397
Author(s):  
D. E. Johnson ◽  
J. Pfeifer
Keyword(s):  
Electron Microscopy ◽  
Image Reconstruction ◽  
High Voltage ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Three Dimensional Reconstruction ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Dimensional Reconstruction ◽  
Quantitative Results

Greatly increased specimen penetration, which is the principle advantage of high voltage electron microscopy, carries with it an increased need for techniques to interpret the large amount of three-dimensional information projected into two-dimensional micrographs. Stereo views can provide very useful information and are widely used. However, for the general specimen, stereo views are limited in their ability to produce quantitative results. At the high voltage microscope facility, Univ. of Wisconsin, we have begun a program to develop and apply three dimensional reconstruction techniques to the microscopy of thick specimens.

scholarly journals Crossover recombination and synapsis are linked by adjacent regions within the N terminus of the Zip1 synaptonemal complex protein

2018 ◽  
Author(s):  
Karen Voelkel-Meiman ◽  
Shun-Yun Cheng ◽  
Melanie Parziale ◽  
Savannah J. Morehouse ◽  
Arden Feil ◽  
...  
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Segregation ◽  
Central Element ◽  
Building Blocks ◽  
Homologous Chromosomes ◽  
Sumo Ligase ◽  
Close Proximity ◽  
N Terminus ◽  
Complex Protein ◽  
Synaptonemal Complex Protein

AbstractAccurate chromosome segregation during meiosis relies on the prior establishment of at least one crossover recombination event between homologous chromosomes, which is often associated with the meiosis-specific MutSγ complex. The recombination intermediates that give rise to MutSγ interhomolog crossovers are embedded within a hallmark meiotic prophase structure called the synaptonemal complex (SC), but the mechanisms that coordinate the processes of SC assembly (synapsis) and crossover recombination remain poorly understood. Among known central region building blocks of the budding yeast SC, the Zip1 protein is unique for its SC-independent role in promoting MutSγ crossovers. Here we report that adjacent regions within Zip1’s unstructured N terminus encompass its crossover and SC assembly functions. We previously showed that deletion of Zip1 residues 21-163 abolishes tripartite SC assembly and prevents the robust SUMOylation of the SC central element component, Ecm11, but allows excess MutSγ crossover recombination. We find the reciprocal phenotype when Zip1 residues 2-9 or 10-14 are deleted; in these mutants SC assembles and Ecm11 is hyperSUMOylated, but MutSγ crossovers are strongly diminished. Interestingly, Zip1 residues 2-9 or 2-14 are required for the normal localization of Zip3, a putative E3 SUMO ligase and pro-MutSγ crossover factor, to Zip1 polycomplex structures and to recombination initiation sites. By contrast, deletion of Zip1 residues 15-20 does not detectably prevent Zip3’s localization at Zip1 polycomplex and supports some MutSγ crossing over but prevents normal SC assembly and robust Ecm11 SUMOylation. These results highlight distinct N terminal regions that are differentially critical for Zip1’s roles in crossover recombination and SC assembly; we speculate that the adjacency of these regions enables Zip1 to serve as a liaison, facilitating crosstalk between the two processes by bringing crossover recombination and synapsis factors in close proximity to one another.

Computer Assisted Image Reconstruction of Oligomer Structure

1976 ◽  
Vol 34 ◽  
pp. 472-473
Author(s):  
A.M. Jones ◽  
A. Max Fiskin
Keyword(s):  
Three Dimensional ◽  
Depth Of Field ◽  
Computer Assisted ◽  
Projection Data ◽  
Two Dimensional ◽  
Single Particles ◽  
Dimensional Reconstruction ◽  
Computer Assisted Image ◽  
The Fourier Transform ◽  
Space Approach

If the tilt of a specimen can be varied either by the strategy of observing identical particles orientated randomly or by use of a eucentric goniometer stage, three dimensional reconstruction procedures are available (l). If the specimens, such as small protein aggregates, lack periodicity, direct space methods compete favorably in ease of implementation with reconstruction by the Fourier (transform) space approach (2). Regardless of method, reconstruction is possible because useful specimen thicknesses are always much less than the depth of field in an electron microscope. Thus electron images record the amount of stain in columns of the object normal to the recording plates. For single particles, practical considerations dictate that the specimen be tilted precisely about a single axis. In so doing a reconstructed image is achieved serially from two-dimensional sections which in turn are generated by a series of back-to-front lines of projection data.

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