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| 2. |
- Agostinho, A., et al.
(författare)
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Sexual dimorphism in the width of the mouse synaptonemal complex
- 2018
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Ingår i: Journal of Cell Science. - : Company of Biologists Ltd. - 0021-9533 .- 1477-9137. ; 131:5
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Tidskriftsartikel (refereegranskat)abstract
- Sexual dimorphism has been used to describe morphological differences between the sexes, but can be extended to any biologically related process that varies between males and females. The synaptonemal complex (SC) is a tripartite structure that connects homologous chromosomes in meiosis. Here, aided by superresolution microscopy techniques, we show that the SC is subject to sexual dimorphism, in mouse germ cells. We have identified a significantly narrower SC in oocytes and have established that this difference does not arise from a different organization of the lateral elements nor from a different isoform of transverse filament protein SYCP1. Instead, we provide evidence for the existence of a narrower central element and a different integration site for the C-termini of SYCP1, in females. In addition to these female-specific features, we speculate that post-translation modifications affecting the SYCP1 coiled-coil region could render a more compact conformation, thus contributing to the narrower SC observed in females.
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| 3. |
- de la Fuente, R, et al.
(författare)
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Epigenetic Dysregulation of Mammalian Male Meiosis Caused by Interference of Recombination and Synapsis
- 2021
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Ingår i: Cells. - : MDPI AG. - 2073-4409. ; 10:9
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Tidskriftsartikel (refereegranskat)abstract
- Meiosis involves a series of specific chromosome events, namely homologous synapsis, recombination, and segregation. Disruption of either recombination or synapsis in mammals results in the interruption of meiosis progression during the first meiotic prophase. This is usually accompanied by a defective transcriptional inactivation of the X and Y chromosomes, which triggers a meiosis breakdown in many mutant models. However, epigenetic changes and transcriptional regulation are also expected to affect autosomes. In this work, we studied the dynamics of epigenetic markers related to chromatin silencing, transcriptional regulation, and meiotic sex chromosome inactivation throughout meiosis in knockout mice for genes encoding for recombination proteins SPO11, DMC1, HOP2 and MLH1, and the synaptonemal complex proteins SYCP1 and SYCP3. These models are defective in recombination and/or synapsis and promote apoptosis at different stages of progression. Our results indicate that impairment of recombination and synapsis alter the dynamics and localization pattern of epigenetic marks, as well as the transcriptional regulation of both autosomes and sex chromosomes throughout prophase-I progression. We also observed that the morphological progression of spermatocytes throughout meiosis and the dynamics of epigenetic marks are processes that can be desynchronized upon synapsis or recombination alteration. Moreover, we detected an overlap of early and late epigenetic signatures in most mutants, indicating that the normal epigenetic transitions are disrupted. This can alter the transcriptional shift that occurs in spermatocytes in mid prophase-I and suggest that the epigenetic regulation of sex chromosomes, but also of autosomes, is an important factor in the impairment of meiosis progression in mammals.
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| 4. |
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| 5. |
- Hernandez-Hernandez, A, et al.
(författare)
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The central element of the synaptonemal complex in mice is organized as a bilayered junction structure
- 2016
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Ingår i: Journal of cell science. - : The Company of Biologists. - 1477-9137 .- 0021-9533. ; 129:11, s. 2239-2249
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Tidskriftsartikel (refereegranskat)abstract
- The synaptonemal complex (SC) transiently stabilizes pairing interactions between homologous chromosomes during meiosis. Assembly of the SC is mediated through integration of opposing transverse filaments (TF) into a central element (CE), a process that is poorly understood. We have here analyzed the localization of the TF protein SYCP1 and the CE proteins SYCE1, SYCE2 and SYCE3 within the central region of the SC in mouse spermatocytes using immunoelectron microscopy. Distribution of immuno-gold particles in a lateral view of the SC, supported by protein interaction data, suggest that the N-terminal region of SYCP1 and SYCE3 form a joint bilayered central structure and that SYCE1 and SYCE2 localize in between the two layers. We find that disruption of SYCE2 and TEX12 (a fourth CE protein) localization to the CE abolishes central alignment of the N-terminal region of SYCP1. Thus, our results show that all four CE proteins in an interdependent manner contribute to stabilization of opposing N-terminal regions of SYCP1, forming a bilayered TF-CE junction structure that promotes SC formation and synapsis.
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| 8. |
- Kumar, R, et al.
(författare)
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MEI4 – a central player in the regulation of meiotic DNA double-strand break formation in the mouse
- 2015
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Ingår i: Journal of cell science. - : The Company of Biologists. - 1477-9137 .- 0021-9533. ; 128:9, s. 1800-1811
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Tidskriftsartikel (refereegranskat)abstract
- The formation of programmed DNA double strand breaks (DSBs) at the beginning of meiotic prophase marks the initiation of meiotic recombination. Meiotic DSBs are catalyzed by SPO11 and their repair takes place on meiotic chromosome axes. The evolutionarily conserved MEI4 protein is required for meiotic DSB formation and is localized on chromosome axes. Here we show that HORMAD1, one of the meiotic chromosome axis components, is required for MEI4 localization. Importantly, the quantitative correlation between the level of axis-associated MEI4 and DSB formation suggests that axis-associated MEI4 could be a limiting factor for DSB formation. We also show that MEI1, REC8 and RAD21L are important for proper MEI4 localization. These findings on MEI4 dynamics during meiotic prophase suggest that the association of MEI4 to chromosome axes is required for DSB formation, and that the loss of this association upon DSB repair could contribute to turning off meiotic DSB formation.
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| 15. |
- Hamer, G, et al.
(författare)
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Characterization of a novel meiosis-specific protein within the central element of the synaptonemal complex
- 2006
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Ingår i: Journal of cell science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 119:19Pt 19, s. 4025-4032
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Tidskriftsartikel (refereegranskat)abstract
- During the first meiotic prophase, alignment and synapsis of the homologous chromosomes are mediated by the synaptonemal complex. Incorrect assembly of this complex results in cell death, impaired meiotic recombination and formation of aneuploid germ cells. We have identified a novel mouse meiosis-specific protein, TEX12, and shown it to be a component of the central element structure of the synaptonemal complex at synapsed homologous chromosomes. Only two other central element proteins, SYCE1 and SYCE2, have been identified to date and, using several mouse knockout models, we show that these proteins and TEX12 specifically depend on the synaptonemal transverse filament protein SYCP1 for localization to the meiotic chromosomes. Additionally, we show that TEX12 exactly co-localized with SYCE2, having the same, often punctate, localization pattern. SYCE1, on the other hand, co-localized with SYCP1 and these proteins displayed the same more continuous expression pattern. These co-localization studies were confirmed by co-immunoprecipitation experiments that showed that TEX12 specifically co-precipitated with SYCE2. Our results suggest a molecular network within the central elements, in which TEX12 and SYCE2 form a complex that interacts with SYCE1. SYCE1 interacts more directly with SYCP1 and could thus anchor the central element proteins to the transverse filaments.
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| 16. |
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| 17. |
- Kouznetsova, A., et al.
(författare)
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Age-dependent aneuploidy in mammalian oocytes instigated at the second meiotic division
- 2022
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Ingår i: Aging Cell. - : Wiley. - 1474-9718 .- 1474-9726. ; 21:7
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Tidskriftsartikel (refereegranskat)abstract
- Ageing severely affects the chromosome segregation process in human oocytes resulting in aneuploidy, infertility and developmental disorders. A considerable amount of segregation errors in humans are introduced at the second meiotic division. We have here compared the chromosome segregation process in young adult and aged female mice during the second meiotic division. More than half of the oocytes in aged mice displayed chromosome segregation irregularities at anaphase II, resulting in dramatically increased level of aneuploidy in haploid gametes, from 4% in young adult mice to 30% in aged mice. We find that the post-metaphase II process that efficiently corrects aberrant kinetochore-microtubule attachments in oocytes in young adult mice is approximately 10-fold less efficient in aged mice, in particular affecting chromosomes that show small inter-centromere distances at the metaphase II stage in aged mice. Our results reveal that post-metaphase II processes have critical impact on age-dependent aneuploidy in mammalian eggs.
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| 18. |
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| 19. |
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| 20. |
- Kouznetsova, A, et al.
(författare)
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BRCA1-mediated chromatin silencing is limited to oocytes with a small number of asynapsed chromosomes
- 2009
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Ingår i: Journal of cell science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 122:14Pt 14, s. 2446-2452
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Tidskriftsartikel (refereegranskat)abstract
- Transcriptional silencing of the sex chromosomes during male meiosis is regarded as a manifestation of a general mechanism active in both male and female germ cells, called meiotic silencing of unsynapsed chromatin (MSUC). MSUC is initiated by the recruitment of the tumor suppressor protein BRCA1 to the axes of unsynapsed chromosomes. We now show that Sycp3, a structural component of the chromosome axis, is required for localization of BRCA1 to unsynapsed pachytene chromosomes. Importantly, we find that oocytes carrying an excess of two to three pairs of asynapsed homologous chromosomes fail to recruit enough BRCA1 to the asynapsed axes to activate MSUC. Furthermore, loss of MSUC function only transiently rescues oocytes from elimination during early postnatal development. The fact that the BRCA1-dependent synapsis surveillance system cannot respond to higher degrees of asynapsis and is dispensable for removal of aberrant oocytes argues that MSUC has a limited input as a quality control mechanism in female germ cells.
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| 21. |
- Kouznetsova, A, et al.
(författare)
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SYCP2 and SYCP3 are required for cohesin core integrity at diplotene but not for centromere cohesion at the first meiotic division
- 2005
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Ingår i: Journal of cell science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 118:10Pt 10, s. 2271-2278
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Tidskriftsartikel (refereegranskat)abstract
- Much of the organization of the meiotic prophase-I chromosome axis is attributed to two groups of proteins: the axial element proteins, SYCP2 and SYCP3; and the cohesin-complex proteins. Although the cohesin-complex proteins ensure that sister chromatids remain paired during meiosis, the role of SYCP2 and SYCP3 is not clear. Interestingly, it has been shown that SYCP3 and SYCP2 associate with the centromere regions of male, but not female, metaphase-I chromosomes, suggesting a sex-specific function for the two proteins. We have analysed the spatial distribution of cohesin-complex proteins associated with meiotic chromosomes in germ cells derived from Sycp3-deficient female and male mice. We show that, in the absence of SYCP3, the cohesin cores associated with the female meiotic chromosomes disassemble prematurely at the diplotene stage of meiosis. We also show that SYCP3 and SYCP2 are not required for centromere cohesion at the metaphase-I stage in male germ cells. We conclude that SYCP3 has a temporally restricted role in maintaining, but not establishing, cohesin-core organization during prophase I. This finding supports a model in which the removal of bulk cohesin from paired sister chromatids at late prophase in both meiotic and mitotic cells ensures proper chromosome compaction and segregation.
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| 23. |
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| 24. |
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| 26. |
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| 27. |
- Sakakibara, Y, et al.
(författare)
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Bivalent separation into univalents precedes age-related meiosis I errors in oocytes
- 2015
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Ingår i: Nature communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 6, s. 7550-
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Tidskriftsartikel (refereegranskat)abstract
- The frequency of chromosome segregation errors during meiosis I (MI) in oocytes increases with age. The two-hit model suggests that errors are caused by the combination of a first hit that creates susceptible crossover configurations and a second hit comprising an age-related reduction in chromosome cohesion. This model predicts an age-related increase in univalents, but direct evidence of this phenomenon as a major cause of segregation errors has been lacking. Here, we provide the first live analysis of single chromosomes undergoing segregation errors during MI in the oocytes of naturally aged mice. Chromosome tracking reveals that 80% of the errors are preceded by bivalent separation into univalents. The set of the univalents is biased towards balanced and unbalanced predivision of sister chromatids during MI. Moreover, we find univalents predisposed to predivision in human oocytes. This study defines premature bivalent separation into univalents as the primary defect responsible for age-related aneuploidy.
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| 28. |
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