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Telomere-independent homologue pairing and checkpoint escape of accessory ring chromosomes in male mouse meiosis.

Voet T, Liebe B, Labaere C, Marynen P, Scherthan H - J. Cell Biol. (2003)

Bottom Line: Fluorescent in situ hybridization and three-dimensional fluorescence microscopy revealed that ring MCs did not participate in meiotic telomere clustering while MC homologues paired at the XY-body periphery.Unaligned MCs triggered the spindle checkpoint leading to apoptosis of metaphase cells.Our findings indicate a telomere-independent mechanism for pairing of mammalian MCs, illuminate escape routes to meiotic checkpoints, and give clues for genetic engineering of germ line-permissive chromosomal vectors.

View Article: PubMed Central - PubMed

Affiliation: Human Genome Laboratory, Department of Human Genetics, Flanders Interuniversity Institute for Biotechnology, University of Leuven, Belgium.

ABSTRACT
We analyzed transmission of a ring minichromosome (MC) through mouse spermatogenesis as a monosome and in the presence of a homologue. Mice, either monosomic or disomic for the MC, produced MC+ offspring. In the monosomic condition, most univalents underwent self-synapsis as indicated by STAG3, SCP3, and SCP1 deposition. Fluorescent in situ hybridization and three-dimensional fluorescence microscopy revealed that ring MCs did not participate in meiotic telomere clustering while MC homologues paired at the XY-body periphery. Self-synapsis of MC(s) and association with the XY-body likely allowed them to pass putative pachytene checkpoints. At metaphase I and II, MC kinetochores assembled MAD2 and BUBR1 spindle checkpoint proteins. Unaligned MCs triggered the spindle checkpoint leading to apoptosis of metaphase cells. Other MCs frequently associated with mouse pericentric heterochromatin, which may have allowed them to pass the spindle checkpoint. Our findings indicate a telomere-independent mechanism for pairing of mammalian MCs, illuminate escape routes to meiotic checkpoints, and give clues for genetic engineering of germ line-permissive chromosomal vectors.

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MCs in MI and MII. (A–D) FISH with an MC chromatid-specific PAC probe (red; see Materials and methods) on MI (A and B) and MII (C and D) spreads of a disomic mouse. (Ai) An MC bivalent, remote from mouse centromeres, displays split FISH signals (arrowheads), indicating maintenance of cohesion at sister centromeres. (Bi) Two MCs showing split chromatid signals (arrowheads) are located separate from each other, but each are associated with a mouse pericentric DAPI-bright heterochromatin block (black in ii). Bar, 5 μm. (Ci) An MC displaying sister chromatid signals (arrowhead) in an MII spermatocyte. Bar, 10 μm. (Di) An MII spermatocyte with one MC with two chromatid signals (arrowhead) and a second MC that is present as a single sister chromatid (arrow) due to loss of sister chromatid cohesion during MI. All DAPI images (Aii–Dii) are shown in grayscale. (Ei) IF staining for STAG3 (red) combined with MC FISH (green) on a meiotic MI showing a STAG3 signal at the MC (arrowhead). (Eii) STAG3 channel only.
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fig6: MCs in MI and MII. (A–D) FISH with an MC chromatid-specific PAC probe (red; see Materials and methods) on MI (A and B) and MII (C and D) spreads of a disomic mouse. (Ai) An MC bivalent, remote from mouse centromeres, displays split FISH signals (arrowheads), indicating maintenance of cohesion at sister centromeres. (Bi) Two MCs showing split chromatid signals (arrowheads) are located separate from each other, but each are associated with a mouse pericentric DAPI-bright heterochromatin block (black in ii). Bar, 5 μm. (Ci) An MC displaying sister chromatid signals (arrowhead) in an MII spermatocyte. Bar, 10 μm. (Di) An MII spermatocyte with one MC with two chromatid signals (arrowhead) and a second MC that is present as a single sister chromatid (arrow) due to loss of sister chromatid cohesion during MI. All DAPI images (Aii–Dii) are shown in grayscale. (Ei) IF staining for STAG3 (red) combined with MC FISH (green) on a meiotic MI showing a STAG3 signal at the MC (arrowhead). (Eii) STAG3 channel only.

Mentions: MC FISH to MIs showed that only 18–44% of the disomic MIs (n = 23; 28 and 9, respectively) contained paired MCs with juxtaposed FISH signals with their DAPI outline touching or overlapping (Fig. 6 A). The remaining disomic MIs contained separated MC signals (Fig. 6 B), which suggests that a significant number of MC bivalents separated precociously.


Telomere-independent homologue pairing and checkpoint escape of accessory ring chromosomes in male mouse meiosis.

Voet T, Liebe B, Labaere C, Marynen P, Scherthan H - J. Cell Biol. (2003)

MCs in MI and MII. (A–D) FISH with an MC chromatid-specific PAC probe (red; see Materials and methods) on MI (A and B) and MII (C and D) spreads of a disomic mouse. (Ai) An MC bivalent, remote from mouse centromeres, displays split FISH signals (arrowheads), indicating maintenance of cohesion at sister centromeres. (Bi) Two MCs showing split chromatid signals (arrowheads) are located separate from each other, but each are associated with a mouse pericentric DAPI-bright heterochromatin block (black in ii). Bar, 5 μm. (Ci) An MC displaying sister chromatid signals (arrowhead) in an MII spermatocyte. Bar, 10 μm. (Di) An MII spermatocyte with one MC with two chromatid signals (arrowhead) and a second MC that is present as a single sister chromatid (arrow) due to loss of sister chromatid cohesion during MI. All DAPI images (Aii–Dii) are shown in grayscale. (Ei) IF staining for STAG3 (red) combined with MC FISH (green) on a meiotic MI showing a STAG3 signal at the MC (arrowhead). (Eii) STAG3 channel only.
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Related In: Results  -  Collection

Show All Figures
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fig6: MCs in MI and MII. (A–D) FISH with an MC chromatid-specific PAC probe (red; see Materials and methods) on MI (A and B) and MII (C and D) spreads of a disomic mouse. (Ai) An MC bivalent, remote from mouse centromeres, displays split FISH signals (arrowheads), indicating maintenance of cohesion at sister centromeres. (Bi) Two MCs showing split chromatid signals (arrowheads) are located separate from each other, but each are associated with a mouse pericentric DAPI-bright heterochromatin block (black in ii). Bar, 5 μm. (Ci) An MC displaying sister chromatid signals (arrowhead) in an MII spermatocyte. Bar, 10 μm. (Di) An MII spermatocyte with one MC with two chromatid signals (arrowhead) and a second MC that is present as a single sister chromatid (arrow) due to loss of sister chromatid cohesion during MI. All DAPI images (Aii–Dii) are shown in grayscale. (Ei) IF staining for STAG3 (red) combined with MC FISH (green) on a meiotic MI showing a STAG3 signal at the MC (arrowhead). (Eii) STAG3 channel only.
Mentions: MC FISH to MIs showed that only 18–44% of the disomic MIs (n = 23; 28 and 9, respectively) contained paired MCs with juxtaposed FISH signals with their DAPI outline touching or overlapping (Fig. 6 A). The remaining disomic MIs contained separated MC signals (Fig. 6 B), which suggests that a significant number of MC bivalents separated precociously.

Bottom Line: Fluorescent in situ hybridization and three-dimensional fluorescence microscopy revealed that ring MCs did not participate in meiotic telomere clustering while MC homologues paired at the XY-body periphery.Unaligned MCs triggered the spindle checkpoint leading to apoptosis of metaphase cells.Our findings indicate a telomere-independent mechanism for pairing of mammalian MCs, illuminate escape routes to meiotic checkpoints, and give clues for genetic engineering of germ line-permissive chromosomal vectors.

View Article: PubMed Central - PubMed

Affiliation: Human Genome Laboratory, Department of Human Genetics, Flanders Interuniversity Institute for Biotechnology, University of Leuven, Belgium.

ABSTRACT
We analyzed transmission of a ring minichromosome (MC) through mouse spermatogenesis as a monosome and in the presence of a homologue. Mice, either monosomic or disomic for the MC, produced MC+ offspring. In the monosomic condition, most univalents underwent self-synapsis as indicated by STAG3, SCP3, and SCP1 deposition. Fluorescent in situ hybridization and three-dimensional fluorescence microscopy revealed that ring MCs did not participate in meiotic telomere clustering while MC homologues paired at the XY-body periphery. Self-synapsis of MC(s) and association with the XY-body likely allowed them to pass putative pachytene checkpoints. At metaphase I and II, MC kinetochores assembled MAD2 and BUBR1 spindle checkpoint proteins. Unaligned MCs triggered the spindle checkpoint leading to apoptosis of metaphase cells. Other MCs frequently associated with mouse pericentric heterochromatin, which may have allowed them to pass the spindle checkpoint. Our findings indicate a telomere-independent mechanism for pairing of mammalian MCs, illuminate escape routes to meiotic checkpoints, and give clues for genetic engineering of germ line-permissive chromosomal vectors.

Show MeSH
Related in: MedlinePlus