Fused sister kinetochores initiate the reductional division in meiosis I

Xuexian Li; R. Kelly Dawe

doi:10.1038/ncb1923

Nonrandom Homolog Segregation at Meiosis I in Schizosaccharomyces pombe Mutants Lacking Recombination

Genetics ◽

10.1093/genetics/163.3.857 ◽

2003 ◽

Vol 163 (3) ◽

pp. 857-874 ◽

Cited By ~ 6

Author(s):

Luther Davis ◽

Gerald R Smith

Keyword(s):

Schizosaccharomyces Pombe ◽

Sister Chromatid ◽

Meiotic Recombination ◽

Meiotic Division ◽

General Feature ◽

Homologous Chromosomes ◽

Chromatid Cohesion ◽

Homozygous Diploid ◽

Reductional Division ◽

Meiosis I

Abstract Physical connection between homologous chromosomes is normally required for their proper segregation to opposite poles at the first meiotic division (MI). This connection is generally provided by the combination of reciprocal recombination and sister-chromatid cohesion. In the absence of meiotic recombination, homologs are predicted to segregate randomly at MI. Here we demonstrate that in rec12 mutants of the fission yeast Schizosaccharomyces pombe, which are devoid of meiosis-induced recombination, homologs segregate to opposite poles at MI 63% of the time. Residual, Rec12-independent recombination appears insufficient to account for the observed nonrandom homolog segregation. Dyad asci are frequently produced by rec12 mutants. More than half of these dyad asci contain two viable homozygous-diploid spores, the products of a single reductional division. This set of phenotypes is shared by other S. pombe mutants that lack meiotic recombination, suggesting that nonrandom MI segregation and dyad formation are a general feature of meiosis in the absence of recombination and are not peculiar to rec12 mutants. Rec8, a meiosis-specific sister-chromatid cohesin, is required for the segregation phenotypes displayed by rec12 mutants. We propose that S. pombe possesses a system independent of recombination that promotes homolog segregation and discuss possible mechanisms.

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Commitment to meiosis in Saccharomyces cerevisiae: involvement of the SPO14 gene.

Genetics ◽

10.1093/genetics/130.4.703 ◽

1992 ◽

Vol 130 (4) ◽

pp. 703-716 ◽

Cited By ~ 5

Author(s):

S M Honigberg ◽

C Conicella ◽

R E Espositio

Keyword(s):

Saccharomyces Cerevisiae ◽

Gene Product ◽

Mitotic Division ◽

Temperature Sensitive ◽

Unusual Property ◽

Phenotypic Analysis ◽

New Gene ◽

Late Stages ◽

Reductional Division ◽

Meiosis I

Abstract This paper describes the identification, cloning and phenotypic analysis of SPO14, a new gene required for meiosis and spore formation. Studies of strains carrying a temperature-sensitive mutation or a disruption/duplication allele indicate that spo14 mutants have the unusual property of being able to return to mitotic division, even from the late stages of meiotic development. Early meiotic events, such as DNA replication and intragenic and intergenic recombination, occur normally. In contrast, later meiotic processes are defective in spo14 mutants: the meiosis I division appears to be executed at slightly depressed levels, the meiosis II division is reduced more severely, and no spores are formed. Epistasis tests using mutants defective in recombination or reductional division support these findings. Based on these data, we suggest that the SPO14 gene product is involved in the coordinate induction of late meiotic events and that this induction is responsible for the phenomenon of commitment.

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Recombination Can Partially Substitute for SPO13 in Regulating Meiosis I in Budding Yeast

Genetics ◽

10.1093/genetics/155.4.1607 ◽

2000 ◽

Vol 155 (4) ◽

pp. 1607-1621 ◽

Cited By ~ 2

Author(s):

Lisa Henninger Rutkowski ◽

Rochelle Easton Esposito

Keyword(s):

Saccharomyces Cerevisiae ◽

Nuclear Division ◽

Crossing Over ◽

Wild Type Allele ◽

Null Mutant ◽

Wild Type ◽

Homologous Chromosomes ◽

Chromosome Synapsis ◽

Reductional Division ◽

Meiosis I

Abstract Recombination and chromosome synapsis bring homologous chromosomes together, creating chiasmata that ensure accurate disjunction during reductional division. SPO13 is a key gene required for meiosis I (MI) reductional segregation, but dispensable for recombination, in Saccharomyces cerevisiae. Absence of SPO13 leads to single-division meiosis where reductional segregation is largely eliminated, but other meiotic events occur relatively normally. This phenotype allows haploids to produce viable meiotic products. Spo13p is thought to act by delaying nuclear division until sister centromeres/chromatids undergo proper cohesion for segregation to the same pole at MI. In the present study, a search for new spo13-like mutations that allow haploid meiosis recovered only new spo13 alleles. Unexpectedly, an unusual reduced-expression allele (spo13-23) was recovered that behaves similarly to a null mutant in haploids but to a wild-type allele in diploids, dependent on the presence of recombining homologs rather than on a diploid genome. This finding demonstrates that in addition to promoting accurate homolog disjunction, recombination can also function to partially substitute for SPO13 in promoting sister cohesion. Analysis of various recombination-defective mutants indicates that this contribution of recombination to reductional segregation requires full levels of crossing over. The implications of these results regarding SPO13 function are discussed.

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Meiotic CENP-C is a shepherd: bridging the space between the centromere and the kinetochore in time and space

Essays in Biochemistry ◽

10.1042/ebc20190080 ◽

2020 ◽

Vol 64 (2) ◽

pp. 251-261

Author(s):

Jessica E. Fellmeth ◽

Kim S. McKim

Keyword(s):

Chromosome Segregation ◽

New Technologies ◽

Early Prophase ◽

Unique Role ◽

Kinetochore Assembly ◽

M Phase ◽

In Vivo Analysis ◽

Meiosis I

Abstract While many of the proteins involved in the mitotic centromere and kinetochore are conserved in meiosis, they often gain a novel function due to the unique needs of homolog segregation during meiosis I (MI). CENP-C is a critical component of the centromere for kinetochore assembly in mitosis. Recent work, however, has highlighted the unique features of meiotic CENP-C. Centromere establishment and stability require CENP-C loading at the centromere for CENP-A function. Pre-meiotic loading of proteins necessary for homolog recombination as well as cohesion also rely on CENP-C, as do the main scaffolding components of the kinetochore. Much of this work relies on new technologies that enable in vivo analysis of meiosis like never before. Here, we strive to highlight the unique role of this highly conserved centromere protein that loads on to centromeres prior to M-phase onset, but continues to perform critical functions through chromosome segregation. CENP-C is not merely a structural link between the centromere and the kinetochore, but also a functional one joining the processes of early prophase homolog synapsis to late metaphase kinetochore assembly and signaling.

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