Meiotic cohesin REC8 marks the axial elements of rat synaptonemal complexes before cohesins SMC1β and SMC3

In meiotic prophase, the sister chromatids of each chromosome develop a common axial element (AE) that is integrated into the synaptonemal complex (SC). We analyzed the incorporation of sister chromatid cohesion proteins (cohesins) and other AE components into AEs. Meiotic cohesin REC8 appeared shortly before premeiotic S phase in the nucleus and formed AE-like structures (REC8-AEs) from premeiotic S phase on. Subsequently, meiotic cohesin SMC1β, cohesin SMC3, and AE proteins SCP2 and SCP3 formed dots along REC8-AEs, which extended and fused until they lined REC8-AEs along their length. In metaphase I, SMC1β, SMC3, SCP2, and SCP3 disappeared from the chromosome arms and accumulated around the centromeres, where they stayed until anaphase II. In striking contrast, REC8 persisted along the chromosome arms until anaphase I and near the centromeres until anaphase II. We propose that REC8 provides a basis for AE formation and that the first steps in AE assembly do not require SMC1β, SMC3, SCP2, and SCP3. Furthermore, SMC1β, SMC3, SCP2, and SCP3 cannot provide arm cohesion during metaphase I. We propose that REC8 then provides cohesion. RAD51 and/or DMC1 coimmunoprecipitates with REC8, suggesting that REC8 may also provide a basis for assembly of recombination complexes.

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Quantitative Cytogenetics Reveals Molecular Stoichiometry and Longitudinal Organization of Meiotic Chromosome Axes and Loops

10.1101/724997 ◽

2019 ◽

Cited By ~ 3

Author(s):

Alexander Woglar ◽

Kei Yamaya ◽

Baptiste Roelens ◽

Alistair Boettiger ◽

Simone Köhler ◽

...

Keyword(s):

Sister Chromatid ◽

De Novo ◽

Meiotic Chromosome ◽

S Phase ◽

C Elegans ◽

Sister Chromatids ◽

Chromatid Cohesion ◽

Molecular Bases ◽

Chromosome Axis ◽

Specialized Organization

ABSTRACTDuring meiosis, chromosomes adopt a specialized organization involving assembly of a cohesin-based axis along their lengths, with DNA loops emanating from this axis. We applied novel, quantitative and widely applicable cytogenetic strategies to elucidate the molecular bases of this organization using C. elegans. Analyses of WT chromosomes and de novo circular mini-chromosomes revealed that meiosis-specific HORMA-domain proteins assemble into cohorts in defined numbers and co-organize the axis together with two functionally-distinct cohesin complexes (REC-8 and COH-3/4) in defined stoichiometry. We further found that REC-8 cohesins, which load during S phase and mediate sister chromatid cohesion, usually occur as individual complexes, supporting a model wherein sister cohesion is mediated locally by a single cohesin ring. REC-8 complexes are interspersed in an alternating pattern with cohorts of axis-organizing COH-3/4 complexes (averaging three per cohort), which are insufficient to confer cohesion but can bind to individual chromatids, suggesting a mechanism to enable formation of asymmetric sister chromatid loops. Indeed, immuno-FISH assays demonstrate frequent asymmetry in genomic content between the loops formed on sister chromatids. We discuss how features of chromosome axis/loop architecture inferred from our data can help to explain enigmatic, yet essential, aspects of the meiotic program.

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Meiosis in triploid Lolium. I. Synaptonemal complex formation and chromosome configurations at metaphase I in aneuploid autotriploid L. multiflorum

Genome ◽

10.1139/g94-025 ◽

1994 ◽

Vol 37 (2) ◽

pp. 181-189 ◽

Cited By ~ 10

Author(s):

Huw M. Thomas ◽

Barry J. Thomas

Keyword(s):

Complex Formation ◽

Synaptonemal Complex ◽

Lolium Multiflorum ◽

Synaptonemal Complexes ◽

Pollen Mother Cells ◽

Partner Exchange ◽

Synaptonemal Complex Formation ◽

Mother Cells ◽

Axial Element ◽

Metaphase I

A spreading technique for synaptonemal complexes (SCs) was applied to pollen mother cells of two aneuploid genotypes of autotriploid Lolium multiflorum (2n = 3x + 1 = 22). In the earliest nuclei analyzed the axial elements are in six groups of 3 and one group of 4. Most groups have formed multivalents with from one to five pairing partner exchanges, but there are also groups that have formed bivalents and univalents. Some axial elements have formed triple associations, in one case for the length of the trivalent. Unsynapsed axial elements remain aligned with their homologous SCs into pachytene, but this alignment is abolished as these axes pair heterologously among themselves until the entire axial element complement is synapsed. At metaphase I most chromosomes are associated as trivalents and quadrivalents.Key words: Lolium, triploid, pairing partner exchange, chiasma, multivalent.

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Maternal Obesity Enhances Oocyte Chromosome Abnormalities Associated With Aging

10.1101/505511 ◽

2018 ◽

Cited By ~ 1

Author(s):

Yan Yun ◽

Zijie Wei ◽

Neil Hunter

Keyword(s):

Sister Chromatid ◽

Maternal Obesity ◽

Sister Chromatid Cohesion ◽

Chromosome Abnormalities ◽

Obese Mice ◽

Sister Chromatids ◽

Chromatid Cohesion ◽

Metaphase I

Obesity is increasing globally and maternal obesity has adverse effects on pregnancy outcomes and the long-term health of offspring. Maternal obesity has been associated with pregnancy failure through impaired oogenesis and embryogenesis. However, whether maternal obesity causes chromosome abnormalities in oocytes has remained unclear. Here we show that chromosome abnormalities are increased in the oocytes of obese mice and identify weakened sister-chromatid cohesion as the likely cause. Numbers of full-grown follicles retrieved from obese mice were the same as controls and the efficiency of in vitro oocyte maturation remained high. However, chromosome abnormalities presenting in both metaphase-I and metaphase-II were elevated, most prominently the premature separation of sister chromatids. Weakened sister-chromatid cohesion in oocytes from obese mice was manifested both as the terminalization of chiasmata in metaphase-I and as increased separation of sister centromeres in metaphase II. Obesity-associated abnormalities were elevated in older mice implying that maternal obesity exacerbates the deterioration of cohesion seen with advancing age.

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Phosphorylation of histone H3 is correlated with changes in the maintenance of sister chromatid cohesion during meiosis in maize, rather than the condensation of the chromatin

Journal of Cell Science ◽

10.1242/jcs.113.18.3217 ◽

2000 ◽

Vol 113 (18) ◽

pp. 3217-3226 ◽

Cited By ~ 3

Author(s):

E. Kaszas ◽

W.Z. Cande

Keyword(s):

Sister Chromatid ◽

Meiotic Chromosome ◽

Histone H3 ◽

Sister Chromatid Cohesion ◽

Chromosome Condensation ◽

Mitotic Chromosomes ◽

Sister Chromatids ◽

H3 Phosphorylation ◽

Chromatid Cohesion ◽

Metaphase I

Meiotic chromosome condensation is a unique process, characterized by dramatic changes in chromosome morphology that are required for the correct progression of pairing, synapsis, recombination and segregation of sister chromatids. We used an antibody that recognizes a ser 10 phosphoepitope on histone H3 to monitor H3 phosphorylation during meiosis in maize meiocytes. H3 phosphorylation has been reported to be an excellent marker for chromosome condensation during mitotic prophase in animal cells. In this study, we find that on maize mitotic chromosomes only pericentromeric regions are stained; there is little staining on the arms. During meiosis, chromosome condensation from leptotene through diplotene occurs in the absence of H3 phosphorylation. Instead, the changes in H3 phosphorylation at different stages of meiosis correlate with the differences in requirements for sister chromatid cohesion at different stages. Just before nuclear envelope breakdown, histone H3 phosphorylation is seen first in the pericentromeric regions and then extends through the arms at metaphase I; at metaphase II only the pericentromeric regions are stained. In afd1 (absence of first division), a mutant that is defective in many aspects of meiosis including sister chromatid cohesion and has equational separation at metaphase I, staining is restricted to the pericentromeric regions during metaphase I and anaphase I; there is no staining at metaphase II or anaphase II. We conclude that changes in the level of phosphorylation of ser10 in H3 correspond to changes in the cohesion of sister chromatids rather than the extent of chromosome condensation at different stages of meiosis.

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Evidence for cohesin sliding along budding yeast chromosomes

Open Biology ◽

10.1098/rsob.150178 ◽

2016 ◽

Vol 6 (6) ◽

pp. 150178 ◽

Cited By ~ 37

Author(s):

Maria Ocampo-Hafalla ◽

Sofía Muñoz ◽

Catarina P. Samora ◽

Frank Uhlmann

Keyword(s):

Chromosome Segregation ◽

Sister Chromatid ◽

Budding Yeast ◽

Transcription Termination ◽

Gene Activation ◽

S Phase ◽

Cohesin Complex ◽

Sister Chromatids ◽

Chromatid Cohesion ◽

Active Genes

The ring-shaped cohesin complex is thought to topologically hold sister chromatids together from their synthesis in S phase until chromosome segregation in mitosis. How cohesin stably binds to chromosomes for extended periods, without impeding other chromosomal processes that also require access to the DNA, is poorly understood. Budding yeast cohesin is loaded onto DNA by the Scc2–Scc4 cohesin loader at centromeres and promoters of active genes, from where cohesin translocates to more permanent places of residence at transcription termination sites. Here we show that, at the GAL2 and MET17 loci, pre-existing cohesin is pushed downstream along the DNA in response to transcriptional gene activation, apparently without need for intermittent dissociation or reloading. We observe translocation intermediates and find that the distribution of most chromosomal cohesin is shaped by transcription. Our observations support a model in which cohesin is able to slide laterally along chromosomes while maintaining topological contact with DNA. In this way, stable cohesin binding to DNA and enduring sister chromatid cohesion become compatible with simultaneous underlying chromosomal activities, including but maybe not limited to transcription.

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MCM2–7-dependent cohesin loading during S phase promotes sister-chromatid cohesion

eLife ◽

10.7554/elife.33920 ◽

2018 ◽

Vol 7 ◽

Cited By ~ 27

Author(s):

Ge Zheng ◽

Mohammed Kanchwala ◽

Chao Xing ◽

Hongtao Yu

Keyword(s):

Sister Chromatid ◽

Replication Fork ◽

Sister Chromatid Cohesion ◽

S Phase ◽

Nucleosome Assembly ◽

Okazaki Fragment ◽

Replicative Helicase ◽

Sister Chromatids ◽

Chromatid Cohesion ◽

Okazaki Fragment Processing

DNA replication transforms cohesin rings dynamically associated with chromatin into the cohesive form to establish sister-chromatid cohesion. Here, we show that, in human cells, cohesin loading onto chromosomes during early S phase requires the replicative helicase MCM2–7 and the kinase DDK. Cohesin and its loader SCC2/4 (NIPBL/MAU2 in humans) associate with DDK and phosphorylated MCM2–7. This binding does not require MCM2–7 activation by CDC45 and GINS, but its persistence on activated MCM2–7 requires fork-stabilizing replisome components. Inactivation of these replisome components impairs cohesin loading and causes interphase cohesion defects. Interfering with Okazaki fragment processing or nucleosome assembly does not impact cohesion. Therefore, MCM2–7-coupled cohesin loading promotes cohesion establishment, which occurs without Okazaki fragment maturation. We propose that the cohesin–loader complex bound to MCM2–7 is mobilized upon helicase activation, transiently held by the replisome, and deposited behind the replication fork to encircle sister chromatids and establish cohesion.

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SOLO: a meiotic protein required for centromere cohesion, coorientation, and SMC1 localization in Drosophila melanogaster

The Journal of Cell Biology ◽

10.1083/jcb.200904040 ◽

2010 ◽

Vol 188 (3) ◽

pp. 335-349 ◽

Cited By ~ 24

Author(s):

Rihui Yan ◽

Sharon E. Thomas ◽

Jui-He Tsai ◽

Yukihiro Yamada ◽

Bruce D. McKee

Keyword(s):

Drosophila Melanogaster ◽

Sister Chromatid ◽

Sister Chromatid Cohesion ◽

Early Prophase ◽

Wild Type ◽

Sister Chromatids ◽

Chromatid Cohesion ◽

Mutant Phenotypes ◽

Meiosis I ◽

Novel Protein

Sister chromatid cohesion is essential to maintain stable connections between homologues and sister chromatids during meiosis and to establish correct centromere orientation patterns on the meiosis I and II spindles. However, the meiotic cohesion apparatus in Drosophila melanogaster remains largely uncharacterized. We describe a novel protein, sisters on the loose (SOLO), which is essential for meiotic cohesion in Drosophila. In solo mutants, sister centromeres separate before prometaphase I, disrupting meiosis I centromere orientation and causing nondisjunction of both homologous and sister chromatids. Centromeric foci of the cohesin protein SMC1 are absent in solo mutants at all meiotic stages. SOLO and SMC1 colocalize to meiotic centromeres from early prophase I until anaphase II in wild-type males, but both proteins disappear prematurely at anaphase I in mutants for mei-S332, which encodes the Drosophila homologue of the cohesin protector protein shugoshin. The solo mutant phenotypes and the localization patterns of SOLO and SMC1 indicate that they function together to maintain sister chromatid cohesion in Drosophila meiosis.

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