Limits...
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.

Show MeSH

Related in: MedlinePlus

MCs assemble a cohesin and AE core. (A) IF staining for STAG3 (red) combined with MC FISH (green) on a monosomic pachytene nucleus. (Aii and Eii) Details showing the respective chromosome core in grayscale. A dotlike STAG3 signal (arrow) is present on the MC. (B) A connecting STAG3-positive structure (arrowhead) between the MC and the cohesin core of a monosomic mouse bivalent. (C–E) IF staining for SCP3 (green) combined with α-satellite MC FISH (red) on pachytene nuclei. (C) A dotlike SCP3 signal (arrow) is detected at the MC in a monosomic spermatocyte nucleus close to the LE of the X chromosome. (Cii) Enlarged detail showing the chromosome core (arrow). (D) A SCP3 rod (arrowhead) connects two MCs in a spermatocyte I of a disomic mouse (note that this is the most extended rod observed). (E) A rodlike SCP3-positive structure (arrowhead) connects the MC with the SC of a monosomic mouse bivalent. (A–E) Images were taken of three-dimensionally preserved nuclei such that the focal planes were at the position of the SCP or STAG3 signals. Bars in Cii and Eii represent 2 μm; bar in Dii is 7 μm. (F) Frequencies of the SCP3 dot- and rodlike staining (based on ≥ 50 nuclei).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2172825&req=5

fig2: MCs assemble a cohesin and AE core. (A) IF staining for STAG3 (red) combined with MC FISH (green) on a monosomic pachytene nucleus. (Aii and Eii) Details showing the respective chromosome core in grayscale. A dotlike STAG3 signal (arrow) is present on the MC. (B) A connecting STAG3-positive structure (arrowhead) between the MC and the cohesin core of a monosomic mouse bivalent. (C–E) IF staining for SCP3 (green) combined with α-satellite MC FISH (red) on pachytene nuclei. (C) A dotlike SCP3 signal (arrow) is detected at the MC in a monosomic spermatocyte nucleus close to the LE of the X chromosome. (Cii) Enlarged detail showing the chromosome core (arrow). (D) A SCP3 rod (arrowhead) connects two MCs in a spermatocyte I of a disomic mouse (note that this is the most extended rod observed). (E) A rodlike SCP3-positive structure (arrowhead) connects the MC with the SC of a monosomic mouse bivalent. (A–E) Images were taken of three-dimensionally preserved nuclei such that the focal planes were at the position of the SCP or STAG3 signals. Bars in Cii and Eii represent 2 μm; bar in Dii is 7 μm. (F) Frequencies of the SCP3 dot- and rodlike staining (based on ≥ 50 nuclei).

Mentions: The fertility of MC+ mice suggests germ line transmission in the presence of one and two (or multiple) MC copies. However, unpaired chromosome cores and absence of recombination appear to have the potential to trigger apoptosis through checkpoint activation in mammalian prophase I (for review see Cohen and Pollard, 2001). Two proteinaceous chromosome core structures, the AE/LE and the cohesin core (Pelttari et al., 2001; Prieto et al., 2002), contribute to correct meiotic chromosome segregation (Petronczki et al., 2003). To investigate whether the MC assembles meiotic chromosome cores, we combined MC-specific FISH with IF staining of STAG3 (a component of meiotic cohesin cores), and SCP3 or SCP1 (SC components) on monosomic and disomic pachytene nuclei. Dotlike STAG3 cohesin signals were seen at 82% of the monosomic nuclei (n = 40; Fig. 2 A), whereas in 15% of the nuclei, a STAG3 signal spanned between the univalent MC and the cohesin core of an adjacent bivalent (Fig. 2 B).


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 assemble a cohesin and AE core. (A) IF staining for STAG3 (red) combined with MC FISH (green) on a monosomic pachytene nucleus. (Aii and Eii) Details showing the respective chromosome core in grayscale. A dotlike STAG3 signal (arrow) is present on the MC. (B) A connecting STAG3-positive structure (arrowhead) between the MC and the cohesin core of a monosomic mouse bivalent. (C–E) IF staining for SCP3 (green) combined with α-satellite MC FISH (red) on pachytene nuclei. (C) A dotlike SCP3 signal (arrow) is detected at the MC in a monosomic spermatocyte nucleus close to the LE of the X chromosome. (Cii) Enlarged detail showing the chromosome core (arrow). (D) A SCP3 rod (arrowhead) connects two MCs in a spermatocyte I of a disomic mouse (note that this is the most extended rod observed). (E) A rodlike SCP3-positive structure (arrowhead) connects the MC with the SC of a monosomic mouse bivalent. (A–E) Images were taken of three-dimensionally preserved nuclei such that the focal planes were at the position of the SCP or STAG3 signals. Bars in Cii and Eii represent 2 μm; bar in Dii is 7 μm. (F) Frequencies of the SCP3 dot- and rodlike staining (based on ≥ 50 nuclei).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172825&req=5

fig2: MCs assemble a cohesin and AE core. (A) IF staining for STAG3 (red) combined with MC FISH (green) on a monosomic pachytene nucleus. (Aii and Eii) Details showing the respective chromosome core in grayscale. A dotlike STAG3 signal (arrow) is present on the MC. (B) A connecting STAG3-positive structure (arrowhead) between the MC and the cohesin core of a monosomic mouse bivalent. (C–E) IF staining for SCP3 (green) combined with α-satellite MC FISH (red) on pachytene nuclei. (C) A dotlike SCP3 signal (arrow) is detected at the MC in a monosomic spermatocyte nucleus close to the LE of the X chromosome. (Cii) Enlarged detail showing the chromosome core (arrow). (D) A SCP3 rod (arrowhead) connects two MCs in a spermatocyte I of a disomic mouse (note that this is the most extended rod observed). (E) A rodlike SCP3-positive structure (arrowhead) connects the MC with the SC of a monosomic mouse bivalent. (A–E) Images were taken of three-dimensionally preserved nuclei such that the focal planes were at the position of the SCP or STAG3 signals. Bars in Cii and Eii represent 2 μm; bar in Dii is 7 μm. (F) Frequencies of the SCP3 dot- and rodlike staining (based on ≥ 50 nuclei).
Mentions: The fertility of MC+ mice suggests germ line transmission in the presence of one and two (or multiple) MC copies. However, unpaired chromosome cores and absence of recombination appear to have the potential to trigger apoptosis through checkpoint activation in mammalian prophase I (for review see Cohen and Pollard, 2001). Two proteinaceous chromosome core structures, the AE/LE and the cohesin core (Pelttari et al., 2001; Prieto et al., 2002), contribute to correct meiotic chromosome segregation (Petronczki et al., 2003). To investigate whether the MC assembles meiotic chromosome cores, we combined MC-specific FISH with IF staining of STAG3 (a component of meiotic cohesin cores), and SCP3 or SCP1 (SC components) on monosomic and disomic pachytene nuclei. Dotlike STAG3 cohesin signals were seen at 82% of the monosomic nuclei (n = 40; Fig. 2 A), whereas in 15% of the nuclei, a STAG3 signal spanned between the univalent MC and the cohesin core of an adjacent bivalent (Fig. 2 B).

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