scholarly journals Abnormal meiotic spindles cause a cascade of defects during spermatogenesis in asp males of Drosophila

Development ◽  
1990 ◽  
Vol 108 (2) ◽  
pp. 251-260
Author(s):  
J. Casal ◽  
C. Gonzalez ◽  
F. Wandosell ◽  
J. Avila ◽  
P. Ripoll
Keyword(s):  
Drosophila Melanogaster ◽  
Variable Size ◽  
Meiotic Spindles ◽  
Spindle Structure ◽  
Size Of Nuclei ◽  
Segregation Of Chromosomes

Since spermatogenesis in Drosophila is a series of interconnected and interdependent steps and most of the spermatogenic events take place in the absence of transcription, failures in a given stage can give rise to a cascade of defects later on. The asp locus of Drosophila melanogaster codes for a non-tubulin component implicated in proper spindle structure and/or function (Ripoll et al. 1985). Homozygous asp males exhibit abnormal meiotic spindles giving rise to altered segregation of chromosomes and mitochondria and failures in cytokinesis. Postmeiotic spermatogenic stages of asp males show a series of alterations that we interpret as due to the previously occurring defective meiosis because meiotic spindles are the only microtubular structure altered in mutant testes. The most conspicuous alterations are: (i) variable size of nuclei and nebenkerns of early spermatids, which are also multinucleate instead of having single and uniformly sized nuclei; (ii) elongating spermatids in which abnormal-sized mitochondrial derivatives elongate alongside more than one axoneme; (iii) failures in the individualization process, where abnormal spermatids remain syncytial, and seem to be eliminated during the coiling stage.

scholarly journals Centromere-proximal meiotic crossovers in Drosophila melanogaster are suppressed by both highly-repetitive heterochromatin and the centromere effect

2019 ◽  
Author(s):  
Michaelyn Hartmann ◽  
James Umbanhowar ◽  
Jeff Sekelsky
Keyword(s):  
Drosophila Melanogaster ◽  
Low Frequency ◽  
Heterochromatic Region ◽  
Bloom Syndrome ◽  
Segregation Of Chromosomes

AbstractCrossovers are essential in meiosis of most organisms to ensure the proper segregation of chromosomes. The lack or improper placement of crossovers can result in nondisjunction and aneuploidy in progeny. Crossovers near the centromere can cause nondisjunction; centromere-proximal crossovers are suppressed by what is termed the centromere effect, but the mechanism is unknown. Here, we investigate contributions to centromere-proximal crossover suppression in Drosophila melanogaster. We mapped a large number of centromere-proximal crossovers and find that crossovers are essentially absent from the highly-repetitive (HR)-heterochromatin surrounding the centromere but occur at a low frequency within the less-repetitive (LR)-heterochromatic region and adjacent euchromatin. Previous research suggested that flies that lack the Bloom syndrome helicase (Blm) lose meiotic of crossover patterning, including the centromere effect. Mapping of centromere-proximal crossovers in Blm mutants reveals that the suppression within the HR-heterochromatin is intact, but the centromere effect is lost. We conclude that centromere-proximal crossovers are suppressed by two separable mechanisms: the HR-heterochromatin effect, which completely suppresses crossovers in the HR-heterochromatin, and the centromere effect, which suppresses crossovers with a dissipating effect with distance from the centromere.

Mitotic spindles of Drosophila melanogaster: a phase-contrast and scanning electron-microscope study

1977 ◽  
Vol 23 (1) ◽  
pp. 43-55
Author(s):  
A. Milsted ◽  
W.D. Cohen ◽  
N. Lampen
Keyword(s):  
Drosophila Melanogaster ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Phase Contrast ◽  
Mitotic Spindles ◽  
Scanning Electron Microscope Study ◽  
Cytoplasmic Material ◽  
Spindle Structure ◽  
Scanning Electron

Mitotic spindles have been isolated from the blastema stage of Drosophila melanogaster embryos using modified tubulin-polymerizing medium. ‘Clean’ spindles, relatively free of contaminating cytoplasmic material, are obtained. Under phase contrast, mitotic stages appear remarkably similar to those seen in situ, as reported in early literature. This preservation of morphological integrity, coupled with relative structural simplicity due to low chromosome number (2n = 8), makes these spindles ideal subjects for study. Use of the scanning electron microscope provides excellent visulization of their general structural organization, changes in whole spindle structure during the course of mitosis, and higher resolution viewing of surface detail than is permitted with light microscopy.

scholarly journals Spherical Spindle Shape Promotes Perpendicular Cortical Orientation by Preventing Isometric Cortical Pulling on both Spindle Poles during C. elegans Female Meiosis

2019 ◽  
Author(s):  
Elizabeth Vargas ◽  
Karen P. McNally ◽  
Daniel B. Cortes ◽  
Michelle T. Panzica ◽  
Amy Shaub-Maddox ◽  
...  
Keyword(s):  
Polar Body ◽  
Spherical Shape ◽  
Viscous Drag ◽  
Female Meiosis ◽  
C Elegans ◽  
Microtubule Severing ◽  
Perpendicular Orientation ◽  
Spindle Poles ◽  
Meiotic Spindles ◽  
Segregation Of Chromosomes

AbstractMeiotic spindles are positioned perpendicular to the oocyte cortex to facilitate segregation of chromosomes into a large egg and a tiny polar body. In C. elegans, spindles are initially ellipsoid and parallel to the cortex before shortening to a spherical shape and rotating to the perpendicular orientation by dynein-driven cortical pulling. The mechanistic connection between spindle shape and rotation has remained elusive. Here we used mutants of the microtubule-severing protein katanin to manipulate spindle shape without eliminating cortical pulling. In a katanin mutant, spindles remained ellipsoid, had pointed poles and became trapped in either a diagonal or a parallel orientation. Results indicated that astral microtubules emanating from both spindle poles initially engage in cortical pulling until microtubules emanating from one pole detach from the cortex allowing pivoting of the spindle. The lower viscous drag experienced by spherical spindles prevented recapture of the cortex by astral microtubules emanating from the detached pole. In addition, maximizing contact between pole dynein and cortical dynein stabilizes round poles in a perpendicular orientation. Spherical spindle shape can thus promote perpendicular orientation by two distinct mechanisms.

scholarly journals Catch and release: 14-3-3 controls Ncd in meiotic spindles

2017 ◽  
Vol 216 (10) ◽  
pp. 3003-3005
Author(s):  
Mary Dasso
Keyword(s):  
Drosophila Melanogaster ◽  
Spindle Assembly ◽  
Aurora B ◽  
Catch And Release ◽  
Cell Biol ◽  
Microtubule Motor ◽  
Meiotic Spindles ◽  
The Right

During Drosophila melanogaster oogenesis, spindle assembly occurs without centrosomes and relies on signals from chromosomes. Beaven et al. (2017. J. Cell. Biol. https://doi.org/10.1083/jcb.201704120) show that 14-3-3 proteins bind and inhibit a key microtubule motor, Ncd, during oogenesis, but Aurora B releases Ncd inhibition near chromosomes, allowing Ncd to work in the right time and place.

scholarly journals KLP-18, a Klp2 Kinesin, Is Required for Assembly of Acentrosomal Meiotic Spindles in Caenorhabditis elegans

2003 ◽  
Vol 14 (11) ◽  
pp. 4458-4469 ◽  
Author(s):  
Christoph Segbert ◽  
Rosemarie Barkus ◽  
Jim Powers ◽  
Susan Strome ◽  
William M. Saxton ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Chromosome Segregation ◽  
Meiotic Chromosome ◽  
Random Pattern ◽  
Mitotic Spindles ◽  
Clear View ◽  
Meiotic Chromosomes ◽  
Meiotic Spindles ◽  
And Function ◽  
Segregation Of Chromosomes

The proper segregation of chromosomes during meiosis or mitosis requires the assembly of well organized spindles. In many organisms, meiotic spindles lack centrosomes. The formation of such acentrosomal spindles seems to involve first assembly or capture of microtubules (MTs) in a random pattern around the meiotic chromosomes and then parallel bundling and bipolar organization by the action of MT motors and other proteins. Here, we describe the structure, distribution, and function of KLP-18, a Caenorhabditis elegans Klp2 kinesin. Previous reports of Klp2 kinesins agree that it concentrates in spindles, but do not provide a clear view of its function. During prometaphase, metaphase, and anaphase, KLP-18 concentrates toward the poles in both meiotic and mitotic spindles. Depletion of KLP-18 by RNA-mediated interference prevents parallel bundling/bipolar organization of the MTs that accumulate around female meiotic chromosomes. Hence, meiotic chromosome segregation fails, leading to haploid or aneuploid embryos. Subsequent assembly and function of centrosomal mitotic spindles is normal except when aberrant maternal chromatin is present. This suggests that although KLP-18 is critical for organizing chromosome-derived MTs into a parallel bipolar spindle, the order inherent in centrosome-derived astral MT arrays greatly reduces or eliminates the need for KLP-18 organizing activity in mitotic spindles.

Author response for "Location and arrangement of campaniform sensilla in Drosophila melanogaster"

2020 ◽  
Author(s):  
Gesa F. Dinges ◽  
Alexander S. Chockley ◽  
Till Bockemühl ◽  
Kei Ito ◽  
Alexander Blanke ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Author Response ◽  
Campaniform Sensilla

3-D reconstruction and analysis of mammalian mitotic spindle structure

1992 ◽  
Vol 50 (1) ◽  
pp. 578-579
Author(s):  
Kent McDonald ◽  
David Mastronarde ◽  
Rubai Ding ◽  
Eileen O'Toole ◽  
J. Richard McIntosh
Keyword(s):  
Cross Sections ◽  
Mitotic Spindle ◽  
Experimental Studies ◽  
Video Camera ◽  
Three Dimensions ◽  
Mitotic Spindles ◽  
Black And White ◽  
Reconstruction Methods ◽  
Spindle Structure ◽  
Tissue Culture Line

Mammalian spindles are generally large and may contain over a thousand microtubules (MTs). For this reason they are difficult to reconstruct in three dimensions and many researchers have chosen to study the smaller and simpler spindles of lower eukaryotes. Nevertheless, the mammalian spindle is used for many experimental studies and it would be useful to know its detailed structure.We have been using serial cross sections and computer reconstruction methods to analyze MT distributions in mitotic spindles of PtK cells, a mammalian tissue culture line. Images from EM negatives are digtized on a light box by a Dage MTI video camera containing a black and white Saticon tube. The signal is digitized by a Parallax 1280 graphics device in a MicroVax III computer. Microtubules are digitized at a magnification such that each is 10-12 pixels in diameter.

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