| 1. |
- Schoch, C. L., et al.
(author)
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A class-wide phylogenetic assessment of Dothideomycetes
- 2009
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In: Studies in mycology. - : Westerdijk Fungal Biodiversity Institute. - 0166-0616 .- 1872-9797. ; 64, s. 1-15
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Research review (peer-reviewed)abstract
- We present a comprehensive phylogeny derived from 5 genes, nucSSU, nucLSU rDNA, TEF1, RPB1 and RPB2, for 356 isolates and 41 families (six newly described in this volume) in Dothideomycetes. All currently accepted orders in the class are represented for the first time in addition to numerous previously unplaced lineages. Subclass Pleosporomycetidae is expanded to include the aquatic order Jahnulales. An ancestral reconstruction of basic nutritional modes supports numerous transitions from saprobic life histories to plant associated and lichenised modes and a transition from terrestrial to aquatic habitats are confirmed. Finally, a genomic comparison of 6 dothideomycete genomes with other fungi finds a high level of unique protein associated with the class, supporting its delineation as a separate taxon.
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| 2. |
- Adelfalk, C, et al.
(author)
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Cohesin SMC1beta protects telomeres in meiocytes
- 2009
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In: The Journal of cell biology. - : Rockefeller University Press. - 1540-8140 .- 0021-9525. ; 187:2, s. 185-199
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Journal article (peer-reviewed)abstract
- Meiosis-specific mammalian cohesin SMC1β is required for complete sister chromatid cohesion and proper axes/loop structure of axial elements (AEs) and synaptonemal complexes (SCs). During prophase I, telomeres attach to the nuclear envelope (NE), but in Smc1β−/− meiocytes, one fifth of their telomeres fail to attach. This study reveals that SMC1β serves a specific role at telomeres, which is independent of its role in determining AE/SC length and loop extension. SMC1β is necessary to prevent telomere shortening, and SMC3, present in all known cohesin complexes, properly localizes to telomeres only if SMC1β is present. Very prominently, telomeres in Smc1β−/− spermatocytes and oocytes loose their structural integrity and suffer a range of abnormalities. These include disconnection from SCs and formation of large telomeric protein–DNA extensions, extended telomere bridges between SCs, ring-like chromosomes, intrachromosomal telomeric repeats, and a reduction of SUN1 foci in the NE. We suggest that a telomere structure protected from DNA rearrangements depends on SMC1β.
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| 3. |
- de Boer, E, et al.
(author)
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Meiotic interference among MLH1 foci requires neither an intact axial element structure nor full synapsis
- 2007
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In: Journal of cell science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 120:5Pt 5, s. 731-736
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Journal article (peer-reviewed)abstract
- During meiosis, homologous chromosomes (homologs) perform reciprocal exchanges (crossovers) at a high frequency. Crossovers display interference, i.e. their spacing is more even than would be expected if they were placed randomly along the chromosomes. Concomitantly with crossover formation, synaptonemal complexes (SCs) appear between homologs: each chromosome forms an axial structure, the axial element (AE); the AEs of homologs align, and numerous transverse filaments connect the AEs to form an SC. Both the AE and the SC have been implicated in the imposition of interference. We investigated whether intact AEs or SCs are required for crossover interference in the mouse, using a mutant lacking AE protein SYCP3, which displays structurally abnormal AEs and incomplete synapsis. We estimated the level of interference from the spacing of immunofluorescent MLH1 foci, which mark almost all crossover sites in the mouse, along the SCs. The levels of interference among MLH1 foci in wild-type and Sycp3–/– mice were comparable, implying that neither an intact AE structure nor full synapsis is required for wild-type levels of interference.
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| 4. |
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| 5. |
- Jochum, K. P., et al.
(author)
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MPI-DING reference glasses for in situ microanalysis: New reference values for element concentrations and isotope ratios
- 2006
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In: Geochemistry Geophysics Geosystems. - 1525-2027. ; 7:15 Febr
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Journal article (peer-reviewed)abstract
- [1] We present new analytical data of major and trace elements for the geological MPI-DING glasses KL2-G, ML3B-G, StHs6/80-G, GOR128-G, GOR132-G, BM90/21-G, T1-G, and ATHO-G. Different analytical methods were used to obtain a large spectrum of major and trace element data, in particular, EPMA, SIMS, LA-ICPMS, and isotope dilution by TIMS and ICPMS. Altogether, more than 60 qualified geochemical laboratories worldwide contributed to the analyses, allowing us to present new reference and information values and their uncertainties ( at 95% confidence level) for up to 74 elements. We complied with the recommendations for the certification of geological reference materials by the International Association of Geoanalysts (IAG). The reference values were derived from the results of 16 independent techniques, including definitive ( isotope dilution) and comparative bulk ( e. g., INAA, ICPMS, SSMS) and microanalytical ( e. g., LA-ICPMS, SIMS, EPMA) methods. Agreement between two or more independent methods and the use of definitive methods provided traceability to the fullest extent possible. We also present new and recently published data for the isotopic compositions of H, B, Li, O, Ca, Sr, Nd, Hf, and Pb. The results were mainly obtained by high-precision bulk techniques, such as TIMS and MC-ICPMS. In addition, LA-ICPMS and SIMS isotope data of B, Li, and Pb are presented.
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| 6. |
- Juhlin, C, et al.
(author)
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Loss of parafibromin expression in a subset of parathyroid adenomas
- 2006
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In: Endocrine-related cancer. - : Bioscientifica. - 1351-0088 .- 1479-6821. ; 13:2, s. 509-523
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Journal article (peer-reviewed)abstract
- Inactivation of the hyperparathyroidism–jaw tumour syndrome (HPT– JT) gene, HRPT2, was recently established as a genetic mechanism in the development of parathyroid tumours. Its encoded protein parafibromin has tumour-suppressor properties that play an important role in tumour development in the parathyroids, jaws and kidneys. Inactivating HRPT2 mutations are common in HPT– JT and parathyroid carcinomas, and have been described in a few cases of parathyroid adenomas with cystic features. In this study, 46 cases of cystic parathyroid adenomas previously investigated for HRPT2 mutations were characterized with regard to MEN1 gene mutations, cyclin D1 expression and parafibromin expression. In normal tissues and cell lines, parafibromin was ubiquitously expressed. Furthermore, parafibromin was detected as a dominating nuclear and a weaker cytoplasmic signal in transfected cell lines. In the three parathyroid tumours with inactivating HRPT2 mutations parafibromin expression was not detectable, and in one of two cases with aberrantly sized parafibromin the protein was delocalized. Both high and low cyclin D1 levels were found among HRPT2-mutated and -unmutated tumours, suggesting that these events are not mutually exclusive in parathyroid tumour development. The presented data suggest that in the majority of benign parathyroid tumours the expression of parafibromin remains unaltered, while the loss of parafibromin expression is strongly indicative of gene inactivation through mutation of the HRPT2 gene.
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| 10. |
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| 11. |
- Staab, C A, et al.
(author)
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Serum-responsive expression of carbonyl-metabolizing enzymes in normal and transformed human buccal keratinocytes
- 2008
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In: Cellular and Molecular Life Sciences (CMLS). - : Springer Science and Business Media LLC. - 1420-682X .- 1420-9071. ; 65:22, s. 3653-3663
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Journal article (peer-reviewed)abstract
- Gene expression of carbonyl-metabolizing enzymes (CMEs) was investigated in normal buccal keratinocytes (NBK) and the transformed buccal keratinocyte lines SVpgC2a and SqCC/Y1. Studies were performed at a serum concentration known to induce terminal squamous differentiation (TSD) in normal cells. Overall, 39 of 58 evaluated CMEs were found to be expressed at the transcript level. Together the transformed cell lines showed altered transcription of eight CME genes compared to NBK, substantiating earlier results. Serum increased transcript levels of ALDH1A3, DHRS3, HPGD and AKR1A1, and decreased those of ALDH4A1 in NBK; of these, the transformed, TSD-deficient cell lines partly retained regulation of ALDH1A3 and DHRS3. Activity measurements in crude cell lysates, including relevant enzymatic inhibitors, indicated significant capacity for CME-mediated xenobiotic metabolism among the cell lines, notably with an increase in serum-differentiated NBK. The results constitute the first evidence for differential CME gene expression and activity in non-differentiated and differentiated states of epithelial cells.
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| 12. |
- Yang, F, et al.
(author)
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Meiotic failure in male mice lacking an X-linked factor
- 2008
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In: Genes & development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 22:5, s. 682-691
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Journal article (peer-reviewed)abstract
- Meiotic silencing of sex chromosomes may cause their depletion of meiosis-specific genes during evolution. Here, we challenge this hypothesis by reporting the identification of TEX11 as the first X-encoded meiosis-specific factor in mice. TEX11 forms discrete foci on synapsed regions of meiotic chromosomes and appears to be a novel constituent of meiotic nodules involved in recombination. Loss of TEX11 function causes chromosomal asynapsis and reduced crossover formation, leading to elimination of spermatocytes, respectively, at the pachytene and anaphase I stages. Specifically, TEX11-deficient spermatocytes with asynapsed autosomes undergo apoptosis at the pachytene stage, while those with only asynapsed sex chromosomes progress. However, cells that survive the pachytene stage display chromosome nondisjunction at the first meiotic division, resulting in cell death and male infertility. TEX11 interacts with SYCP2, which is an integral component of the synaptonemal complex lateral elements. Thus, TEX11 promotes initiation and/or maintenance of synapsis and formation of crossovers, and may provide a physical link between these two meiotic processes.
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| 13. |
- Costa, Y, et al.
(author)
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Two novel proteins recruited by synaptonemal complex protein 1 (SYCP1) are at the centre of meiosis
- 2005
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In: Journal of cell science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 118:12Pt 12, s. 2755-2762
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Journal article (peer-reviewed)abstract
- Completion of meiosis in mammals depends on the formation of the synaptonemal complex, a tripartite structure that physically links homologous chromosomes during prophase I. Several components of the synaptonemal complex are known, including constituents of the cohesin core, the axial/lateral element and the transverse filaments. No protein has previously been identified as an exclusive component of the central element. Mutations in some synaptonemal-complex proteins results in impaired meiosis. In humans, cases of male infertility have been associated with failure to build the synaptonemal complex. To search for new components of the meiotic machinery, we have used data from microarray expression profiling and found two proteins localising solely to the central element of the mammalian synaptonemal complex. These new proteins, SYCE1 and CESC1, interact with the transverse filament protein SYCP1, and their localisation to the central element appears to depend on recruitment by SYCP1. This suggests a role for SYCE1 and CESC1 in synaptonemal-complex assembly, and perhaps also stability and recombination.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
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| 18. |
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| 19. |
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| 20. |
- Hamer, G, et al.
(author)
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Characterization of a novel meiosis-specific protein within the central element of the synaptonemal complex
- 2006
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In: Journal of cell science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 119:19Pt 19, s. 4025-4032
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Journal article (peer-reviewed)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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| 21. |
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| 22. |
- Hamer, G, et al.
(author)
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Progression of meiotic recombination requires structural maturation of the central element of the synaptonemal complex
- 2008
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In: Journal of cell science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 121:15Pt 15, s. 2445-2451
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Journal article (peer-reviewed)abstract
- The synaptonemal complex is an elaborate meiosis-specific supramolecular protein assembly that promotes chromosome synapsis and meiotic recombination. We inactivated the meiosis-specific gene Tex12 and found that TEX12 is essential for progression of meiosis in both male and female germ cells. Structural analysis of the synaptonemal complex in Tex12–/– meiocytes revealed a disrupted central element structure, a dense structure residing between the synapsed homologous chromosomes. Chromosome synapsis is initiated at multiple positions along the paired homologous chromosomes in Tex12–/– meiotic cells, but fails to propagate along the chromosomes. Furthermore, although meiotic recombination is initiated in Tex12–/– meiotic cells, these early recombination events do not develop into meiotic crossovers. Hence, the mere initiation of synapsis is not sufficient to support meiotic crossing-over. Our results show that TEX12 is a component of the central element structure of the synaptonemal complex required for propagation of synapsis along the paired homologous chromosomes and maturation of early recombination events into crossovers.
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| 23. |
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| 24. |
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| 25. |
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| 26. |
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| 27. |
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| 28. |
- Kouznetsova, A, et al.
(author)
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BRCA1-mediated chromatin silencing is limited to oocytes with a small number of asynapsed chromosomes
- 2009
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In: Journal of cell science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 122:14Pt 14, s. 2446-2452
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Journal article (peer-reviewed)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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| 29. |
- Kouznetsova, A, et al.
(author)
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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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In: Journal of cell science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 118:10Pt 10, s. 2271-2278
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Journal article (peer-reviewed)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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| 30. |
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| 31. |
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| 32. |
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| 33. |
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| 34. |
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| 35. |
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| 36. |
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| 37. |
- Lundell, C., et al.
(author)
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Effects of confined geometry on phase-separated dextran/gelatine mixtures exposed to shear
- 2005
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In: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 288:1, s. 222-229
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Journal article (peer-reviewed)abstract
- The effect of shear on aqueous phase-separated dextran/fish gelatine mixtures with a total concentration of 5 and 10% was studied in a confined geometry. It was measured as a function of composition, strain rate and gap size. This was done by using both small-angle light scattering and a shear cell combined with a confocal laser scanning microscope. At a total polymer concentration of 5%, small-angle light scattering results showed that up to 100 s-1 the deformation of the domains increases with the strain rate. At strain rates less than 100 s-1, the response of the system to strain is dominated by strain rate-dependent deformation. At a higher strain rate there might be balance between break-up and re-coalescence. At a total concentration of 10%, small effects of the gap size were found. In confined geometry, the coalescence rate was faster than expected from viscous hydrodynamic growth. The microscope images showed that the gelatine-enriched phase forms a wetting layer on the surface of the glass wall. The degree of wetting appears to increase with increasing the strain rate up to 60 s -1 and decreases again at higher strain rates. © 2005 Elsevier Inc. All rights reserved.
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| 38. |
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| 39. |
- Novak, I, et al.
(author)
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Cohesin Smc1beta determines meiotic chromatin axis loop organization
- 2008
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In: The Journal of cell biology. - : Rockefeller University Press. - 1540-8140 .- 0021-9525. ; 180:1, s. 83-90
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Journal article (peer-reviewed)abstract
- Meiotic chromosomes consist of proteinaceous axial structures from which chromatin loops emerge. Although we know that loop density along the meiotic chromosome axis is conserved in organisms with different genome sizes, the basis for the regular spacing of chromatin loops and their organization is largely unknown. We use two mouse model systems in which the postreplicative meiotic chromosome axes in the mutant oocytes are either longer or shorter than in wild-type oocytes. We observe a strict correlation between chromosome axis extension and a general and reciprocal shortening of chromatin loop size. However, in oocytes with a shorter chromosome axis, only a subset of the chromatin loops is extended. We find that the changes in chromatin loop size observed in oocytes with shorter or longer chromosome axes depend on the structural maintenance of chromosomes 1β (Smc1β), a mammalian chromosome–associated meiosis-specific cohesin. Our results suggest that in addition to its role in sister chromatid cohesion, Smc1β determines meiotic chromatin loop organization.
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| 40. |
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| 41. |
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| 42. |
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| 43. |
- Schmitt, J, et al.
(author)
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Transmembrane protein Sun2 is involved in tethering mammalian meiotic telomeres to the nuclear envelope
- 2007
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 104:18, s. 7426-7431
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Journal article (peer-reviewed)abstract
- Dynamic repositioning of telomeres is a unique feature of meiotic prophase I that is highly conserved among eukaryotes. At least in fission yeast it was shown to be required for proper alignment and recombination of homologous chromosomes. On entry into meiosis telomeres attach to the nuclear envelope and transiently cluster at a limited area to form a chromosomal bouquet. Telomere clustering is thought to promote chromosome recognition and stable pairing of the homologs. However, the molecular basis of telomere attachment and movement is largely unknown. Here we report that mammalian SUN-domain protein Sun2 specifically localizes to the nuclear envelope attachment sites of meiotic telomeres. Sun2–telomere association is maintained throughout the dynamic movement of telomeres. This association does not require the assembly of chromosomal axial elements or the presence of A-type lamins. Detailed EM analysis revealed that Sun2 is part of a membrane-spanning fibrillar complex that interconnects attached telomeres with cytoplasmic structures. Together with recent findings in fission yeast, our study indicates that the molecular mechanisms required for tethering meiotic telomeres and their dynamic movements during bouquet formation are conserved among eukaryotes.
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| 44. |
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| 46. |
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| 48. |
- Wang, H, et al.
(author)
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Structural damage to meiotic chromosomes impairs DNA recombination and checkpoint control in mammalian oocytes
- 2006
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In: The Journal of cell biology. - : Rockefeller University Press. - 0021-9525 .- 1540-8140. ; 173:4, s. 485-495
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Journal article (peer-reviewed)abstract
- Meiosis in human oocytes is a highly error-prone process with profound effects on germ cell and embryo development. The synaptonemal complex protein 3 (SYCP3) transiently supports the structural organization of the meiotic chromosome axis. Offspring derived from murine Sycp3−/− females die in utero as a result of aneuploidy. We studied the nature of the proximal chromosomal defects that give rise to aneuploidy in Sycp3−/− oocytes and how these errors evade meiotic quality control mechanisms. We show that DNA double-stranded breaks are inefficiently repaired in Sycp3−/− oocytes, thereby generating a temporal spectrum of recombination errors. This is indicated by a strong residual γH2AX labeling retained at late meiotic stages in mutant oocytes and an increased persistence of recombination-related proteins associated with meiotic chromosomes. Although a majority of the mutant oocytes are rapidly eliminated at early postnatal development, a subset with a small number of unfinished crossovers evades the DNA damage checkpoint, resulting in the formation of aneuploid gametes.
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| 49. |
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