scholarly journals Principles of Meiotic Chromosome Assembly

2018 ◽  
Author(s):  
Stephanie A. Schalbetter ◽  
Geoffrey Fudenberg ◽  
Jonathan Baxter ◽  
Katherine S. Pollard ◽  
Matthew J. Neale
Keyword(s):  
Essential Role ◽  
Genomic Sequence ◽  
Meiotic Chromosome ◽  
Three Dimensional ◽  
Interaction Patterns ◽  
Chromosome Synapsis ◽  
Convergent Transcription ◽  
Evolutionarily Conserved ◽  
Chromosome Organisation

AbstractDuring meiotic prophase, chromosomes organise into a series of chromatin loops emanating from a proteinaceous axis, but the mechanisms of assembly remain unclear. Here we elucidate how this elaborate three-dimensional chromosome organisation is underpinned by genomic sequence in Saccharomyces cerevisiae. Entering meiosis, strong cohesin-dependent grid-like Hi-C interaction patterns emerge, reminiscent of mammalian interphase organisation, but with distinct regulation. Meiotic patterns agree with simulations of loop extrusion limited by barriers, yet are patterned by convergent transcription rather than binding of the mammalian interphase factor, CTCF, which is absent in S. cerevisiae—thereby both challenging and extending current paradigms of local chromosome organisation. While grid-like interactions emerge independently of meiotic chromosome synapsis, synapsis itself generates additional compaction that matures differentially according to telomere proximity and chromosome size. Collectively, our results elucidate fundamental principles of chromosome assembly and demonstrate the essential role of cohesin within this evolutionarily conserved process.

scholarly journals Principles of meiotic chromosome assembly revealed in S. cerevisiae

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Stephanie A. Schalbetter ◽  
Geoffrey Fudenberg ◽  
Jonathan Baxter ◽  
Katherine S. Pollard ◽  
Matthew J. Neale
Keyword(s):  
Genomic Sequence ◽  
Meiotic Chromosome ◽  
Three Dimensional ◽  
Heterogeneous Population ◽  
Interaction Patterns ◽  
Chromosome Synapsis ◽  
Barrier Formation ◽  
Evolutionarily Conserved ◽  
Chromosome Organisation

Abstract During meiotic prophase, chromosomes organise into a series of chromatin loops emanating from a proteinaceous axis, but the mechanisms of assembly remain unclear. Here we use Saccharomyces cerevisiae to explore how this elaborate three-dimensional chromosome organisation is linked to genomic sequence. As cells enter meiosis, we observe that strong cohesin-dependent grid-like Hi-C interaction patterns emerge, reminiscent of mammalian interphase organisation, but with distinct regulation. Meiotic patterns agree with simulations of loop extrusion with growth limited by barriers, in which a heterogeneous population of expanding loops develop along the chromosome. Importantly, CTCF, the factor that imposes similar features in mammalian interphase, is absent in S. cerevisiae, suggesting alternative mechanisms of barrier formation. While grid-like interactions emerge independently of meiotic chromosome synapsis, synapsis itself generates additional compaction that matures differentially according to telomere proximity and chromosome size. Collectively, our results elucidate fundamental principles of chromosome assembly and demonstrate the essential role of cohesin within this evolutionarily conserved process.

scholarly journals A molecular model for the role of SYCP3 in meiotic chromosome organisation

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Johanna Liinamaria Syrjänen ◽  
Luca Pellegrini ◽  
Owen Richard Davies
Keyword(s):  
Molecular Model ◽  
Meiotic Chromosome ◽  
Lateral Element ◽  
Homologous Chromosomes ◽  
Meiotic Chromosomes ◽  
Double Stranded Dna ◽  
Evolutionarily Conserved ◽  
20 Nm ◽  
Chromosome Organisation

The synaptonemal complex (SC) is an evolutionarily-conserved protein assembly that holds together homologous chromosomes during prophase of the first meiotic division. Whilst essential for meiosis and fertility, the molecular structure of the SC has proved resistant to elucidation. The SC protein SYCP3 has a crucial but poorly understood role in establishing the architecture of the meiotic chromosome. Here we show that human SYCP3 forms a highly-elongated helical tetramer of 20 nm length. N-terminal sequences extending from each end of the rod-like structure bind double-stranded DNA, enabling SYCP3 to link distant sites along the sister chromatid. We further find that SYCP3 self-assembles into regular filamentous structures that resemble the known morphology of the SC lateral element. Together, our data form the basis for a model in which SYCP3 binding and assembly on meiotic chromosomes leads to their organisation into compact structures compatible with recombination and crossover formation.

scholarly journals Spin wave mediated unidirectional vortex core reversal by two orthogonal monopolar field pulses: The essential role of three-dimensional magnetization dynamics

2016 ◽  
Vol 119 (17) ◽  
pp. 173901 ◽  
Author(s):  
Matthias Noske ◽  
Hermann Stoll ◽  
Manfred Fähnle ◽  
Ajay Gangwar ◽  
Georg Woltersdorf ◽  
...  
Keyword(s):  
Spin Wave ◽  
Vortex Core ◽  
Essential Role ◽  
Three Dimensional ◽  
Magnetization Dynamics

Identification and analysis ofDYAD: a gene required for meiotic chromosome organisation and female meiotic progression inArabidopsis

Development ◽  
2002 ◽  
Vol 129 (16) ◽  
pp. 3935-3943 ◽  
Author(s):  
Bhavna Agashe ◽  
Chellapilla Krishna Prasad ◽  
Imran Siddiqi
Keyword(s):  
Meiotic Chromosome ◽  
Metaphase Plate ◽  
Specific Marker ◽  
Female Meiosis ◽  
Meiotic Progression ◽  
Putative Protein ◽  
Chromosome Synapsis ◽  
Bivalent Formation ◽  
Chromosome Organisation ◽  
Novel Protein

The dyad mutant of Arabidopsis was previously identified as being defective in female meiosis. We report here the analysis of the DYAD gene. In ovules and anthers DYAD RNA is detected specifically in female and male meiocytes respectively, in premeiotic interphase/meiotic prophase. Analysis of chromosome spreads in female meiocytes showed that in the mutant, chromosomes did not undergo synapsis and formed ten univalents instead of five bivalents. Unlike mutations in AtDMC1 and AtSPO11 which also affect bivalent formation as the univalent chromosomes segregate randomly, the dyad univalents formed an ordered metaphase plate and underwent an equational division. This suggests a requirement for DYAD for chromosome synapsis and centromere configuration in female meiosis. The dyad mutant showed increased and persistent expression of a meiosis-specific marker, pAtDMC1::GUS during female meiosis, indicative of defective meiotic progression. The sequence of the putative protein encoded by DYAD did not reveal strong similarity to other proteins. DYAD is therefore likely to encode a novel protein required for meiotic chromosome organisation and female meiotic progression.

WIPI β-propellers in autophagy-related diseases and longevity

2013 ◽  
Vol 41 (4) ◽  
pp. 962-967 ◽  
Author(s):  
Daniela Bakula ◽  
Zsuzsanna Takacs ◽  
Tassula Proikas-Cezanne
Keyword(s):  
Essential Role ◽  
Mammalian Target Of Rapamycin ◽  
Membrane Vesicles ◽  
Catabolic Pathway ◽  
Autophagosome Formation ◽  
Cytoplasmic Material ◽  
Evolutionarily Conserved ◽  
Initiation Step ◽  
Conserved Amino Acids

Autophagy is a catabolic pathway in which the cell sequesters cytoplasmic material, including long-lived proteins, lipids and organelles, in specialized double-membrane vesicles, called autophagosomes. Subsequently, autophagosomes communicate with the lysosomal compartment and acquire acidic hydrolases for final cargo degradation. This process of partial self-eating secures the survival of eukaryotic cells during starvation periods and is critically regulated by mTORC1 (mammalian target of rapamycin complex 1). Under nutrient-poor conditions, inhibited mTORC1 permits localized PtdIns(3)P production at particular membranes that contribute to autophagosome formation. Members of the human WIPI (WD-repeat protein interacting with phosphoinositides) family fulfil an essential role as PtdIns(3)P effectors at the initiation step of autophagosome formation. In the present article, we discuss the role of human WIPIs in autophagy, and the identification of evolutionarily conserved amino acids of WIPI-1 that confer PtdIns(3)P binding downstream of mTORC1 inhibition. We also discuss the PtdIns(3)P effector function of WIPIs in the context of longevity and autophagy-related human diseases, such as cancer and neurodegeneration.

scholarly journals Topoisomerases Modulate the Timing of Meiotic DNA Breakage and Chromosome Morphogenesis in Saccharomyces cerevisiae

Genetics ◽  
2020 ◽  
Vol 215 (1) ◽  
pp. 59-73 ◽  
Author(s):  
Jonna Heldrich ◽  
Xiaoji Sun ◽  
Luis A. Vale-Silva ◽  
Tovah E. Markowitz ◽  
Andreas Hochwagen
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Meiotic Prophase ◽  
Meiotic Chromosome ◽  
Strand Break ◽  
Temperature Sensitive ◽  
Chromosomal Dna ◽  
Link Type ◽  
Chromosome Synapsis ◽  
Intergenic Regions

During meiotic prophase, concurrent transcription, recombination, and chromosome synapsis place substantial topological strain on chromosomal DNA, but the role of topoisomerases in this context remains poorly defined. Here, we analyzed the roles of topoisomerases I and II (Top1 and Top2) during meiotic prophase in Saccharomyces cerevisiae. We show that both topoisomerases accumulate primarily in promoter-containing intergenic regions of actively transcribing genes, including many meiotic double-strand break (DSB) hotspots. Despite the comparable binding patterns, top1 and top2 mutations have different effects on meiotic recombination. TOP1 disruption delays DSB induction and shortens the window of DSB accumulation by an unknown mechanism. By contrast, temperature-sensitive top2-1 mutants exhibit a marked delay in meiotic chromosome remodeling and elevated DSB signals on synapsed chromosomes. The problems in chromosome remodeling were linked to altered Top2 binding patterns rather than a loss of Top2 catalytic activity, and stemmed from a defect in recruiting the chromosome remodeler Pch2/TRIP13 to synapsed chromosomes. No chromosomal defects were observed in the absence of TOP1. Our results imply independent roles for Top1 and Top2 in modulating meiotic chromosome structure and recombination.

scholarly journals Exploring Mondrian Compositions in Three-Dimensional Space

Leonardo ◽  
2020 ◽  
Vol 53 (1) ◽  
pp. 63-69
Author(s):  
Jasmina Stevanov ◽  
Johannes M. Zanker
Keyword(s):  
Interior Design ◽  
Architectural Design ◽  
Essential Role ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Physical Constraints ◽  
Standards Of Beauty ◽  
Perceptual Factors ◽  
Three Dimensional Space

The dogmatic nature of Piet Mondrian’s neoplasticism manifesto initiated a discourse about translating aesthetic ideals from paintings to 3D structures. Mondrian rarely ventured into architectural design, and his unique interior design of “Salon de Madame B … à Dresden” was not executed. The authors discuss physical constraints and perceptual factors that conflict with neoplastic ideals. Using physical and virtual models of the salon, the authors demonstrate challenges with perspective projections and show how such distortions could be minimized in a cylinder. The paradoxical percept elicited by a “reverspective” Mondrian-like space further highlights the essential role of perceptual processes in reaching neoplastic standards of beauty.

scholarly journals The Centriole Cartwheel Protein SAS-6 in Trypanosoma brucei Is Required for Probasal Body Biogenesis and Flagellum Assembly

2015 ◽  
Vol 14 (9) ◽  
pp. 898-907 ◽  
Author(s):  
Huiqing Hu ◽  
Yi Liu ◽  
Qing Zhou ◽  
Sara Siegel ◽  
Ziyin Li
Keyword(s):  
Cell Cycle ◽  
Rna Interference ◽  
Trypanosoma Brucei ◽  
Basal Body ◽  
Essential Role ◽  
Microtubule Organizing Center ◽  
Content Type ◽  
Evolutionarily Conserved ◽  
Organizing Center

ABSTRACT The centriole in eukaryotes functions as the cell's microtubule-organizing center (MTOC) to nucleate spindle assembly, and its biogenesis requires an evolutionarily conserved protein, SAS-6, which assembles the centriole cartwheel. Trypanosoma brucei , an early branching protozoan, possesses the basal body as its MTOC to nucleate flagellum biogenesis. However, little is known about the components of the basal body and their roles in basal body biogenesis and flagellum assembly. Here, we report that the T. brucei SAS-6 homolog, TbSAS-6, is localized to the mature basal body and the probasal body throughout the cell cycle. RNA interference (RNAi) of TbSAS-6 inhibited probasal body biogenesis, compromised flagellum assembly, and caused cytokinesis arrest. Surprisingly, overexpression of TbSAS-6 in T. brucei also impaired probasal body duplication and flagellum assembly, contrary to SAS-6 overexpression in humans, which produces supernumerary centrioles. Furthermore, we showed that depletion of T. brucei Polo-like kinase, TbPLK, or inhibition of TbPLK activity did not abolish TbSAS-6 localization to the basal body, in contrast to the essential role of Polo-like kinase in recruiting SAS-6 to centrioles in animals. Altogether, these results identified the essential role of TbSAS-6 in probasal body biogenesis and flagellum assembly and suggest the presence of a TbPLK-independent pathway governing basal body duplication in T. brucei .

scholarly journals Essential role of c-myb in definitive hematopoiesis is evolutionarily conserved

2010 ◽  
Vol 107 (40) ◽  
pp. 17304-17308 ◽  
Author(s):  
C. Soza-Ried ◽  
I. Hess ◽  
N. Netuschil ◽  
M. Schorpp ◽  
T. Boehm
Keyword(s):  
Essential Role ◽  
Evolutionarily Conserved ◽  
Definitive Hematopoiesis
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