Synaptic configuration of quadrivalents and their association with the XY bivalent in spermatocytes of Robertsonian heterozygotes of Mus domesticus
Abstract Background The nuclear architecture of meiotic prophase spermatocytes is based on higher–order patterns of spatial associations among chromosomal domains and consequently is prone to modification by chromosomal rearrangements. We have shown that nuclear architecture is modified i...
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Sociedad de Biología de Chile
2017
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oai:scielo:S0716-976020170001004052018-01-08Synaptic configuration of quadrivalents and their association with the XY bivalent in spermatocytes of Robertsonian heterozygotes of Mus domesticusBerríos,SoledadFernández–Donoso,RaúlAyarza,Eliana Quadrivalents Robertsonian chromosomes Mouse spermatocytes Nucleoli Nuclear architecture Abstract Background The nuclear architecture of meiotic prophase spermatocytes is based on higher–order patterns of spatial associations among chromosomal domains and consequently is prone to modification by chromosomal rearrangements. We have shown that nuclear architecture is modified in spermatocytes of Robertsonian (Rb) homozygotes of Mus domesticus. In this study we analyse the synaptic configuration of the quadrivalents formed in the meiotic pro– phase of spermatocytes of mice double heterozygotes for the dependent Rb chromosomes: Rbs 11.16 and 16.17. Results Electron microscope spreads of 60 pachytene spermatocytes from four animals of Mus domesticus 2n = 38 were studied and their respective quadrivalents analysed in detail. Normal synaptonemal complex was found between arms 16 of the Rb metacentric chromosomes, telocentrics 11 and 17 and homologous arms of the Rb metacentric chromosomes. About 43% of the quadrivalents formed a synaptonemal complex between the heterologous short arms of chromosomes 11 and 17. This synaptonemal complex is bound to the nuclear envelope through a fourth synapsed telomere, thus dragging the entire quadrivalent to the nuclear envelope. About 57% of quadrivalents showed unsynapsed single axes in the short arms of the telocentric chromosomes. About 90% of these unsynapsed quadrivalents also showed a telomere–to–telomere association between one of the single axes of the telocentric chromosome 11 or 17 and the X chromosome single axis, which was otherwise normally paired with the Y chromosome. Nucleolar material was associated with two bivalents and with the quadrivalent. Conclusions The spermatocytes of heterozygotes for dependent Rb chromosomes formed a quadrivalent where four chromosomes are synapsed together and bound to the nuclear envelope through four telomeres. The nuclear configuration is determined by the fourth shortest telomere, which drags the centromere regions and heterochromatin of all the chromosomes towards the nuclear envelope, favouring the reiterated encounter and eventual rearrangement between the heterologous chromosomes. The unsynapsed regions of quadrivalents are frequently bound to the single axis of the X chromosome, possibly perturbing chromatin condensation and gene expression.info:eu-repo/semantics/openAccessSociedad de Biología de ChileBiological Research v.50 20172017-01-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602017000100405en10.1186/s40659-017-0143-6 |
| institution |
Scielo Chile |
| collection |
Scielo Chile |
| language |
English |
| topic |
Quadrivalents Robertsonian chromosomes Mouse spermatocytes Nucleoli Nuclear architecture |
| spellingShingle |
Quadrivalents Robertsonian chromosomes Mouse spermatocytes Nucleoli Nuclear architecture Berríos,Soledad Fernández–Donoso,Raúl Ayarza,Eliana Synaptic configuration of quadrivalents and their association with the XY bivalent in spermatocytes of Robertsonian heterozygotes of Mus domesticus |
| description |
Abstract Background The nuclear architecture of meiotic prophase spermatocytes is based on higher–order patterns of spatial associations among chromosomal domains and consequently is prone to modification by chromosomal rearrangements. We have shown that nuclear architecture is modified in spermatocytes of Robertsonian (Rb) homozygotes of Mus domesticus. In this study we analyse the synaptic configuration of the quadrivalents formed in the meiotic pro– phase of spermatocytes of mice double heterozygotes for the dependent Rb chromosomes: Rbs 11.16 and 16.17. Results Electron microscope spreads of 60 pachytene spermatocytes from four animals of Mus domesticus 2n = 38 were studied and their respective quadrivalents analysed in detail. Normal synaptonemal complex was found between arms 16 of the Rb metacentric chromosomes, telocentrics 11 and 17 and homologous arms of the Rb metacentric chromosomes. About 43% of the quadrivalents formed a synaptonemal complex between the heterologous short arms of chromosomes 11 and 17. This synaptonemal complex is bound to the nuclear envelope through a fourth synapsed telomere, thus dragging the entire quadrivalent to the nuclear envelope. About 57% of quadrivalents showed unsynapsed single axes in the short arms of the telocentric chromosomes. About 90% of these unsynapsed quadrivalents also showed a telomere–to–telomere association between one of the single axes of the telocentric chromosome 11 or 17 and the X chromosome single axis, which was otherwise normally paired with the Y chromosome. Nucleolar material was associated with two bivalents and with the quadrivalent. Conclusions The spermatocytes of heterozygotes for dependent Rb chromosomes formed a quadrivalent where four chromosomes are synapsed together and bound to the nuclear envelope through four telomeres. The nuclear configuration is determined by the fourth shortest telomere, which drags the centromere regions and heterochromatin of all the chromosomes towards the nuclear envelope, favouring the reiterated encounter and eventual rearrangement between the heterologous chromosomes. The unsynapsed regions of quadrivalents are frequently bound to the single axis of the X chromosome, possibly perturbing chromatin condensation and gene expression. |
| author |
Berríos,Soledad Fernández–Donoso,Raúl Ayarza,Eliana |
| author_facet |
Berríos,Soledad Fernández–Donoso,Raúl Ayarza,Eliana |
| author_sort |
Berríos,Soledad |
| title |
Synaptic configuration of quadrivalents and their association with the XY bivalent in spermatocytes of Robertsonian heterozygotes of Mus domesticus |
| title_short |
Synaptic configuration of quadrivalents and their association with the XY bivalent in spermatocytes of Robertsonian heterozygotes of Mus domesticus |
| title_full |
Synaptic configuration of quadrivalents and their association with the XY bivalent in spermatocytes of Robertsonian heterozygotes of Mus domesticus |
| title_fullStr |
Synaptic configuration of quadrivalents and their association with the XY bivalent in spermatocytes of Robertsonian heterozygotes of Mus domesticus |
| title_full_unstemmed |
Synaptic configuration of quadrivalents and their association with the XY bivalent in spermatocytes of Robertsonian heterozygotes of Mus domesticus |
| title_sort |
synaptic configuration of quadrivalents and their association with the xy bivalent in spermatocytes of robertsonian heterozygotes of mus domesticus |
| publisher |
Sociedad de Biología de Chile |
| publishDate |
2017 |
| url |
http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602017000100405 |
| work_keys_str_mv |
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| _version_ |
1718441566959304704 |