scholarly journals Inverted meiosis: an alternative way of chromosome segregation for reproduction

2020 ◽  
Vol 52 (7) ◽  
pp. 702-707 ◽  
Author(s):  
Wenzhu Li ◽  
Xiangwei He
Keyword(s):  
Dna Replication ◽  
Fission Yeast ◽  
Chromosome Segregation ◽  
Chromosome Structure ◽  
Adaptive Strategy ◽  
Homologous Chromosomes ◽  
Working Model ◽  
Sister Chromatids ◽  
Holocentric Chromosome ◽  
Inverted Order

Abstract Canonical meiosis is characterized by two sequential rounds of nuclear divisions following one round of DNA replication—reductional segregation of homologous chromosomes during the first division and equational segregation of sister chromatids during the second division. Meiosis in an inverted order of two nuclear divisions—inverted meiosis has been observed in several species with holocentromeres as an adaptive strategy to overcome the obstacle in executing a canonical meiosis due to the holocentric chromosome structure. Recent findings of co-existence of inverted and canonical meiosis in two monocentric organisms, human and fission yeast, suggested that inverted meiosis could be common and also lead to the puzzle regarding the mechanistic feasibility for executing two meiosis programs simultaneously. Here, we discuss apparent conflicts for concurrent canonical meiosis and inverted meiosis. Furthermore, we attempt to provide a working model that may be compatible for both forms of meiosis.

Centromere Mapping Functions for Aneuploid Meiotic Products: Analysis of rec8, rec10 and rec11 Mutants of the Fission Yeast Schizosaccharomyces pombe

Genetics ◽  
1999 ◽  
Vol 153 (1) ◽  
pp. 49-55 ◽  
Author(s):  
Michelle D Krawchuk ◽  
Wayne P Wahls
Keyword(s):  
Fission Yeast ◽  
Chromosome Segregation ◽  
Sister Chromatid ◽  
Meiotic Division ◽  
Homologous Chromosomes ◽  
Mapping Functions ◽  
Sister Chromatids ◽  
Chromatid Cohesion ◽  
Products Analysis ◽  
Meiosis I

AbstractRecent evidence suggests that the position of reciprocal recombination events (crossovers) is important for the segregation of homologous chromosomes during meiosis I and sister chromatids during meiosis II. We developed genetic mapping functions that permit the simultaneous analysis of centromere-proximal crossover recombination and the type of segregation error leading to aneuploidy. The mapping functions were tested in a study of the rec8, rec10, and rec11 mutants of fission yeast. In each mutant we monitored each of the three chromosome pairs. Between 38 and 100% of the chromosome segregation errors in the rec8 mutants were due to meiosis I nondisjunction of homologous chromosomes. The remaining segregation errors were likely the result of precocious separation of sister chromatids, a previously described defect in the rec8 mutants. Between 47 and 100% of segregation errors in the rec10 and rec11 mutants were due to nondisjunction of sister chromatids during meiosis II. In addition, centromere-proximal recombination was reduced as much as 14-fold or more on chromosomes that had experienced nondisjunction. These results demonstrate the utility of the new mapping functions and support models in which sister chromatid cohesion and crossover position are important determinants for proper chromosome segregation in each meiotic division.

scholarly journals Direct evaluation of cohesin-mediated sister kinetochore associations at meiosis I in fission yeast

2021 ◽  
Author(s):  
Masashi Nambu ◽  
Atsuki Kishikawa ◽  
Takatomi Yamada ◽  
Kento Ichikawa ◽  
Yunosuke Kira ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Chromosome Segregation ◽  
Mitotic Chromosomes ◽  
Direct Evaluation ◽  
Homologous Chromosomes ◽  
Sister Chromatids ◽  
Pheromone Signaling ◽  
Sister Kinetochore ◽  
Novel Method ◽  
Meiosis I

Kinetochores drive chromosome segregation by mediating chromosome interactions with the spindle. In higher eukaryotes, sister kinetochores are separately positioned on opposite sides of sister centromeres during mitosis, but associate with each other during meiosis I. Kinetochore association facilitates the attachment of sister chromatids to the same pole, enabling the segregation of homologous chromosomes toward opposite poles. In the fission yeast, Schizosaccharomyces pombe, Rec8-containing meiotic cohesin is suggested to establish kinetochore associations by mediating cohesion of the centromere cores. However, cohesin-mediated kinetochore associations on intact chromosomes have never been demonstrated directly. Here, we describe a novel method for the direct evaluation of kinetochore associations on intact chromosomes in live S. pombe cells, and demonstrate that sister kinetochores and the centromere cores are positioned separately on mitotic chromosomes but associate with each other on meiosis I chromosomes. Furthermore, we demonstrate that kinetochore association depends on meiotic cohesin and the cohesin regulators, Moa1 and Mrc1, and requires mating-pheromone signaling for its establishment. These results confirm cohesin-mediated kinetochore association and its regulatory mechanisms, along with the usefulness of the developed method for its analysis.

scholarly journals Shugoshin Promotes Sister Kinetochore Biorientation in Saccharomyces cerevisiae

2008 ◽  
Vol 19 (3) ◽  
pp. 1199-1209 ◽  
Author(s):  
Brendan M. Kiburz ◽  
Angelika Amon ◽  
Adele L. Marston
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Chromosome Segregation ◽  
Minor Role ◽  
Meiotic Cell ◽  
Homologous Chromosomes ◽  
Cell Divisions ◽  
Sister Chromatids ◽  
Sister Kinetochore ◽  
A Minor ◽  
Meiosis I

Chromosome segregation must be executed accurately during both mitotic and meiotic cell divisions. Sgo1 plays a key role in ensuring faithful chromosome segregation in at least two ways. During meiosis this protein regulates the removal of cohesins, the proteins that hold sister chromatids together, from chromosomes. During mitosis, Sgo1 is required for sensing the absence of tension caused by sister kinetochores not being attached to microtubules emanating from opposite poles. Here we describe a differential requirement for Sgo1 in the segregation of homologous chromosomes and sister chromatids. Sgo1 plays only a minor role in segregating homologous chromosomes at meiosis I. In contrast, Sgo1 is important to bias sister kinetochores toward biorientation. We suggest that Sgo1 acts at sister kinetochores to promote their biorientation.

scholarly journals Chiasmata and the kinetochore component Dam1 are crucial for elimination of erroneous chromosome attachments and centromere oscillation at meiosis I

Open Biology ◽  
2021 ◽  
Vol 11 (2) ◽  
Author(s):  
Misuzu Wakiya ◽  
Eriko Nishi ◽  
Shinnosuke Kawai ◽  
Kohei Yamada ◽  
Kazuhiro Katsumata ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Spindle Pole ◽  
Oriented Attachment ◽  
Aurora B ◽  
Correction Factors ◽  
Homologous Chromosomes ◽  
Spindle Poles ◽  
Sister Chromatids ◽  
Potential Link ◽  
Meiosis I

Establishment of proper chromosome attachments to the spindle requires elimination of erroneous attachments, but the mechanism of this process is not fully understood. During meiosis I, sister chromatids attach to the same spindle pole (mono-oriented attachment), whereas homologous chromosomes attach to opposite poles (bi-oriented attachment), resulting in homologous chromosome segregation. Here, we show that chiasmata that link homologous chromosomes and kinetochore component Dam1 are crucial for elimination of erroneous attachments and oscillation of centromeres between the spindle poles at meiosis I in fission yeast. In chiasma-forming cells, Mad2 and Aurora B kinase, which provides time for attachment correction and destabilizes erroneous attachments, respectively, caused elimination of bi-oriented attachments of sister chromatids, whereas in chiasma-lacking cells, they caused elimination of mono-oriented attachments. In chiasma-forming cells, in addition, homologous centromere oscillation was coordinated. Furthermore, Dam1 contributed to attachment elimination in both chiasma-forming and chiasma-lacking cells, and drove centromere oscillation. These results demonstrate that chiasmata alter attachment correction patterns by enabling error correction factors to eliminate bi-oriented attachment of sister chromatids, and suggest that Dam1 induces elimination of erroneous attachments. The coincidental contribution of chiasmata and Dam1 to centromere oscillation also suggests a potential link between centromere oscillation and attachment elimination.

Live observation of fission yeast meiosis in recombination-deficient mutants

2001 ◽  
Vol 114 (15) ◽  
pp. 2843-2853 ◽  
Author(s):  
Monika Molnar ◽  
Jürg Bähler ◽  
Jürg Kohli ◽  
Yasushi Hiraoka
Keyword(s):  
Fission Yeast ◽  
Chromosome Segregation ◽  
Meiotic Division ◽  
Chiasma Formation ◽  
Homologous Chromosomes ◽  
Yeast Meiosis ◽  
Mutant Cells ◽  
Random Level ◽  
Meiosis I ◽  
Chromosome Disjunction

Regular segregation of homologous chromosomes during meiotic divisions is essential for the generation of viable progeny. In recombination-proficient organisms, chromosome disjunction at meiosis I generally occurs by chiasma formation between the homologs (chiasmate meiosis). We have studied meiotic stages in living rec8 and rec7 mutant cells of fission yeast, with special attention to prophase and the first meiotic division. Both rec8 and rec7 are early recombination mutants, and in rec7 mutants, chromosome segregation at meiosis I occurs without any recombination (achiasmate meiosis). Both mutants showed distinct irregularities in nuclear prophase movements. Additionally, rec7 showed an extended first division of variable length and with single chromosomes changing back and forth between the cell poles. Two other early recombination deficient mutants (rec14 and rec15) showed very similar phenotypes to rec7 during the first meiotic division, and the fidelity of achiasmate chromosome segregation slightly exceeded the expected random level. We discuss possible regulatory mechanisms of fission yeast to deal with achiasmate chromosome segregation.

scholarly journals Loss of Cell Cycle Checkpoint Control in Drosophila Rfc4 Mutants

2001 ◽  
Vol 21 (15) ◽  
pp. 5156-5168 ◽  
Author(s):  
Sue A. Krause ◽  
Marie-Louise Loupart ◽  
Sharron Vass ◽  
Stefan Schoenfelder ◽  
Steve Harrison ◽  
...  
Keyword(s):  
Dna Replication ◽  
Chromosome Segregation ◽  
Mitotic Chromosome ◽  
Chromosome Structure ◽  
Cell Cycle Checkpoint ◽  
Replication Factor C ◽  
Checkpoint Control ◽  
Direct Role ◽  
Cycle Checkpoint ◽  
Factor C

ABSTRACT Two alleles of the Drosophila melanogaster Rfc4(DmRfc4) gene, which encodes subunit 4 of the replication factor C (RFC) complex, cause striking defects in mitotic chromosome cohesion and condensation. These mutations produce larval phenotypes consistent with a role in DNA replication but also result in mitotic chromosomal defects appearing either as premature chromosome condensation-like or precocious sister chromatid separation figures. Though the DmRFC4 protein localizes to all replicating nuclei, it is dispersed from chromatin in mitosis. Thus the mitotic defects appear not to be the result of a direct role for RFC4 in chromosome structure. We also show that the mitotic defects in these twoDmRfc4 alleles are the result of aberrant checkpoint control in response to DNA replication inhibition or damage to chromosomes. Not all surveillance function is compromised in these mutants, as the kinetochore attachment checkpoint is operative. Intriguingly, metaphase delay is frequently observed with the more severe of the two alleles, indicating that subsequent chromosome segregation may be inhibited. This is the first demonstration that subunit 4 of RFC functions in checkpoint control in any organism, and our findings additionally emphasize the conserved nature of RFC's involvement in checkpoint control in multicellular eukaryotes.

scholarly journals Centromere repositioning causes inversion of meiosis and generates a reproductive barrier

2019 ◽  
Vol 116 (43) ◽  
pp. 21580-21591 ◽  
Author(s):  
Min Lu ◽  
Xiangwei He
Keyword(s):  
Meiotic Chromosome ◽  
Feedback Mechanism ◽  
Reproductive Barrier ◽  
Evolutionary Time ◽  
Homologous Chromosomes ◽  
Sister Chromatids ◽  
Inverted Order ◽  
Canonical Order ◽  
Evolutionary New Centromeres

The chromosomal position of each centromere is determined epigenetically and is highly stable, whereas incremental cases have supported the occurrence of centromere repositioning on an evolutionary time scale (evolutionary new centromeres, ENCs), which is thought to be important in speciation. The mechanisms underlying the high stability of centromeres and its functional significance largely remain an enigma. Here, in the fission yeast Schizosaccharomyces pombe, we identify a feedback mechanism: The kinetochore, whose assembly is guided by the centromere, in turn, enforces centromere stability. Upon going through meiosis, specific inner kinetochore mutations induce centromere repositioning—inactivation of the original centromere and formation of a new centromere elsewhere—in 1 of the 3 chromosomes at random. Repositioned centromeres reside asymmetrically in the pericentromeric regions and cells carrying them are competent in mitosis and homozygotic meiosis. However, when cells carrying a repositioned centromere are crossed with those carrying the original centromere, the progeny suffer severe lethality due to defects in meiotic chromosome segregation. Thus, repositioned centromeres constitute a reproductive barrier that could initiate genetic divergence between 2 populations with mismatched centromeres, documenting a functional role of ENCs in speciation. Surprisingly, homozygotic repositioned centromeres tend to undergo meiosis in an inverted order—that is, sister chromatids segregate first, and homologous chromosomes separate second—whereas the original centromeres on other chromosomes in the same cell undergo meiosis in the canonical order, revealing hidden flexibility in the perceived rigid process of meiosis.

scholarly journals A stochastic model of kinetochore–microtubule attachment accurately describes fission yeast chromosome segregation

2012 ◽  
Vol 196 (6) ◽  
pp. 757-774 ◽  
Author(s):  
Guillaume Gay ◽  
Thibault Courtheoux ◽  
Céline Reyes ◽  
Sylvie Tournier ◽  
Yannick Gachet
Keyword(s):  
Fission Yeast ◽  
Chromosome Segregation ◽  
Aurora B ◽  
Segregation Behavior ◽  
Microtubule Attachment ◽  
Anaphase Onset ◽  
Sister Chromatids ◽  
Yeast Chromosome ◽  
Spindle Microtubules ◽  
Early Mitosis

In fission yeast, erroneous attachments of spindle microtubules to kinetochores are frequent in early mitosis. Most are corrected before anaphase onset by a mechanism involving the protein kinase Aurora B, which destabilizes kinetochore microtubules (ktMTs) in the absence of tension between sister chromatids. In this paper, we describe a minimal mathematical model of fission yeast chromosome segregation based on the stochastic attachment and detachment of ktMTs. The model accurately reproduces the timing of correct chromosome biorientation and segregation seen in fission yeast. Prevention of attachment defects requires both appropriate kinetochore orientation and an Aurora B–like activity. The model also reproduces abnormal chromosome segregation behavior (caused by, for example, inhibition of Aurora B). It predicts that, in metaphase, merotelic attachment is prevented by a kinetochore orientation effect and corrected by an Aurora B–like activity, whereas in anaphase, it is corrected through unbalanced forces applied to the kinetochore. These unbalanced forces are sufficient to prevent aneuploidy.

scholarly journals Condensin restructures chromosomes in preparation for meiotic divisions

2004 ◽  
Vol 167 (4) ◽  
pp. 613-625 ◽  
Author(s):  
Raymond C. Chan ◽  
Aaron F. Severson ◽  
Barbara J. Meyer
Keyword(s):  
Caenorhabditis Elegans ◽  
Chromosome Segregation ◽  
Germ Cells ◽  
Protein Complex ◽  
Mitotic Chromosome ◽  
Meiotic Chromosome ◽  
Ordered Structure ◽  
Homologous Chromosomes ◽  
Sister Chromatids ◽  
Chromosome Resolution

The production of haploid gametes from diploid germ cells requires two rounds of meiotic chromosome segregation after one round of replication. Accurate meiotic chromosome segregation involves the remodeling of each pair of homologous chromosomes around the site of crossover into a highly condensed and ordered structure. We showed that condensin, the protein complex needed for mitotic chromosome compaction, restructures chromosomes during meiosis in Caenorhabditis elegans. In particular, condensin promotes both meiotic chromosome condensation after crossover recombination and the remodeling of sister chromatids. Condensin helps resolve cohesin-independent linkages between sister chromatids and alleviates recombination-independent linkages between homologues. The safeguarding of chromosome resolution by condensin permits chromosome segregation and is crucial for the formation of discrete, individualized bivalent chromosomes.

scholarly journals Correct spindle elongation at the metaphase/anaphase transition is an APC-dependent event in budding yeast

2001 ◽  
Vol 155 (5) ◽  
pp. 711-718 ◽  
Author(s):  
Fedor Severin ◽  
Anthony A. Hyman ◽  
Simonetta Piatti
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Chromosome Segregation ◽  
Sister Chromatid ◽  
Budding Yeast ◽  
Sister Chromatid Cohesion ◽  
Anaphase Promoting Complex ◽  
Sister Chromatids ◽  
Chromatid Cohesion ◽  
Spindle Elongation

At the metaphase to anaphase transition, chromosome segregation is initiated by the splitting of sister chromatids. Subsequently, spindles elongate, separating the sister chromosomes into two sets. Here, we investigate the cell cycle requirements for spindle elongation in budding yeast using mutants affecting sister chromatid cohesion or DNA replication. We show that separation of sister chromatids is not sufficient for proper spindle integrity during elongation. Rather, successful spindle elongation and stability require both sister chromatid separation and anaphase-promoting complex activation. Spindle integrity during elongation is dependent on proteolysis of the securin Pds1 but not on the activity of the separase Esp1. Our data suggest that stabilization of the elongating spindle at the metaphase to anaphase transition involves Pds1-dependent targets other than Esp1.

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