Limits...
Meiotic telomere protein Ndj1p is required for meiosis-specific telomere distribution, bouquet formation and efficient homologue pairing.

Trelles-Sticken E, Dresser ME, Scherthan H - J. Cell Biol. (2000)

Bottom Line: Since ndj1Delta meiocytes fail to cluster their telomeres at any prophase stage, Ndj1p is the first protein shown to be required for bouquet formation in a synaptic organism.Analysis of homologue pairing by two-color fluorescence in situ hybridization with cosmid probes to regions on III, IX, and XI revealed that disruption of bouquet formation is associated with a significant delay (>2 h) of homologue pairing.Under naturally occurring conditions, bouquet formation may allow for rapid sporulation and confer a selective advantage.

View Article: PubMed Central - PubMed

Affiliation: Department of Human Biology and Genetics, University of Kaiserslautern, D-67653 Kaiserslautern, Germany.

ABSTRACT
We have investigated the requirements for NDJ1 in meiotic telomere redistribution and clustering in synchronized cultures of Saccharomyces cerevisiae. On induction of wild-type meiosis, telomeres disperse from premeiotic aggregates over the nuclear periphery, and then cluster near the spindle pole body (bouquet arrangement) before dispersing again. In ndj1Delta meiocytes, telomeres are scattered throughout the nucleus and fail to form perinuclear meiosis-specific distribution patterns, suggesting that Ndj1p may function to tether meiotic telomeres to the nuclear periphery. Since ndj1Delta meiocytes fail to cluster their telomeres at any prophase stage, Ndj1p is the first protein shown to be required for bouquet formation in a synaptic organism. Analysis of homologue pairing by two-color fluorescence in situ hybridization with cosmid probes to regions on III, IX, and XI revealed that disruption of bouquet formation is associated with a significant delay (>2 h) of homologue pairing. An increased and persistent fraction of ndj1Delta meiocytes with Zip1p polycomplexes suggests that chromosome polarization is important for synapsis progression. Thus, our observations support the hypothesis that meiotic telomere clustering contributes to efficient homologue alignment and synaptic pairing. Under naturally occurring conditions, bouquet formation may allow for rapid sporulation and confer a selective advantage.

Show MeSH

Related in: MedlinePlus

Two-color FISH with cosmid probes m (III, green) and p (IX, red) to spread nuclei of SK1 meiocytes. Nuclei were taken at t = 180 min. (a) Spread nucleus with cosmid signals apart. (b) Meiocyte with both pairs of homologous cosmid signals paired. Therefore, the signals appear enlarged. Bar, 5 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2189801&req=5

Figure 10: Two-color FISH with cosmid probes m (III, green) and p (IX, red) to spread nuclei of SK1 meiocytes. Nuclei were taken at t = 180 min. (a) Spread nucleus with cosmid signals apart. (b) Meiocyte with both pairs of homologous cosmid signals paired. Therefore, the signals appear enlarged. Bar, 5 μm.

Mentions: Since a mutant with disrupted bouquet formation offers the possibility to test for the impact of meiotic telomere clustering for the homologue pairing process, we investigated homologue pairing by FISH with cosmid probes to regions on chromosmes III, IX, and XI (Fig. 1) during wild-type and mutant sporulation. While chromosomes XI represents a large chromosome that is capable spanning the entire nuclear volume, IX is of intermediate size, and III is among the smallest yeast chromosomes. Due to the clustering of vegetative centromeres at the spindle pole body (Hayashi et al. 1998, Jin et al. 1998) and other functions, the yeast nucleus displays a substantial amount of premeiotic homologue association (Loidl et al. 1994; Weiner and Kleckner 1994; Burgess et al. 1999). Pairing interactions are disrupted during premeiotic S-phase, and then return at meiosis-specific levels that well exceed vegetative levels (Loidl et al. 1994; Weiner and Kleckner 1994; Nag et al. 1995; Trelles-Sticken et al. 1999). In the present investigation, pairing of homologous chromosome regions was determined by FISH of two differentially labeled cosmid probes to two-dimensional nuclear spreads that yields two signals pairs in the same focal plane. Spreading has been shown to enhance cytological resolution in the unfavorably small yeast nucleus and to dissociate weak chromosome interactions while leaving stable interactions intact (see Weiner and Kleckner 1994; Nag et al. 1995; Jin et al. 1998). We regarded homologous regions paired when cosmid signals of the same color were touching each other or formed an enlarged confluent signal (Fig. 10 b). To ensure saturated target regions, only nucleoids containing strong signals of both colors were analyzed. Two-color FISH with cosmid pairs f/l and m/p (see Fig. 1 and Fig. 10) was performed on nuclear spreads obtained from meiotic time courses of ndj1Δ and wild-type cells. In initial experiments, we determined the frequencies of associations between heterologously colored signals, which provides a measure for accidental signal contacts. Both wild-type and mutant time courses displayed nearly identical frequencies of heterologous signal associations at 0, 3, 5, and 7 h in sporulation. Specifically, at all time points, the mean fraction of successfully hybridized spreads showing heterologous signal contacts for cosmid combinations f/l and m/p was 8.5% (range 7.3–8.9) and 9.3% (range 9–10.2), respectively. These values are well in agreement with estimations reported by others (see Burgess et al. 1999). To adjust for accidental contacts between cosmid signals, which may be influenced by a number of parameters (see above), we used centromere distant probes and furthermore subtracted 50% of the obtained fraction showing heterologous contacts from the obtained pairing values, since in two cosmid FISH experiments a signal has a two- to fourfold higher probability to be associated with a heterologous than with a homologous signal. It should be noted that the results obtained with and without such a correction remained essentially the same (not shown).


Meiotic telomere protein Ndj1p is required for meiosis-specific telomere distribution, bouquet formation and efficient homologue pairing.

Trelles-Sticken E, Dresser ME, Scherthan H - J. Cell Biol. (2000)

Two-color FISH with cosmid probes m (III, green) and p (IX, red) to spread nuclei of SK1 meiocytes. Nuclei were taken at t = 180 min. (a) Spread nucleus with cosmid signals apart. (b) Meiocyte with both pairs of homologous cosmid signals paired. Therefore, the signals appear enlarged. Bar, 5 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2189801&req=5

Figure 10: Two-color FISH with cosmid probes m (III, green) and p (IX, red) to spread nuclei of SK1 meiocytes. Nuclei were taken at t = 180 min. (a) Spread nucleus with cosmid signals apart. (b) Meiocyte with both pairs of homologous cosmid signals paired. Therefore, the signals appear enlarged. Bar, 5 μm.
Mentions: Since a mutant with disrupted bouquet formation offers the possibility to test for the impact of meiotic telomere clustering for the homologue pairing process, we investigated homologue pairing by FISH with cosmid probes to regions on chromosmes III, IX, and XI (Fig. 1) during wild-type and mutant sporulation. While chromosomes XI represents a large chromosome that is capable spanning the entire nuclear volume, IX is of intermediate size, and III is among the smallest yeast chromosomes. Due to the clustering of vegetative centromeres at the spindle pole body (Hayashi et al. 1998, Jin et al. 1998) and other functions, the yeast nucleus displays a substantial amount of premeiotic homologue association (Loidl et al. 1994; Weiner and Kleckner 1994; Burgess et al. 1999). Pairing interactions are disrupted during premeiotic S-phase, and then return at meiosis-specific levels that well exceed vegetative levels (Loidl et al. 1994; Weiner and Kleckner 1994; Nag et al. 1995; Trelles-Sticken et al. 1999). In the present investigation, pairing of homologous chromosome regions was determined by FISH of two differentially labeled cosmid probes to two-dimensional nuclear spreads that yields two signals pairs in the same focal plane. Spreading has been shown to enhance cytological resolution in the unfavorably small yeast nucleus and to dissociate weak chromosome interactions while leaving stable interactions intact (see Weiner and Kleckner 1994; Nag et al. 1995; Jin et al. 1998). We regarded homologous regions paired when cosmid signals of the same color were touching each other or formed an enlarged confluent signal (Fig. 10 b). To ensure saturated target regions, only nucleoids containing strong signals of both colors were analyzed. Two-color FISH with cosmid pairs f/l and m/p (see Fig. 1 and Fig. 10) was performed on nuclear spreads obtained from meiotic time courses of ndj1Δ and wild-type cells. In initial experiments, we determined the frequencies of associations between heterologously colored signals, which provides a measure for accidental signal contacts. Both wild-type and mutant time courses displayed nearly identical frequencies of heterologous signal associations at 0, 3, 5, and 7 h in sporulation. Specifically, at all time points, the mean fraction of successfully hybridized spreads showing heterologous signal contacts for cosmid combinations f/l and m/p was 8.5% (range 7.3–8.9) and 9.3% (range 9–10.2), respectively. These values are well in agreement with estimations reported by others (see Burgess et al. 1999). To adjust for accidental contacts between cosmid signals, which may be influenced by a number of parameters (see above), we used centromere distant probes and furthermore subtracted 50% of the obtained fraction showing heterologous contacts from the obtained pairing values, since in two cosmid FISH experiments a signal has a two- to fourfold higher probability to be associated with a heterologous than with a homologous signal. It should be noted that the results obtained with and without such a correction remained essentially the same (not shown).

Bottom Line: Since ndj1Delta meiocytes fail to cluster their telomeres at any prophase stage, Ndj1p is the first protein shown to be required for bouquet formation in a synaptic organism.Analysis of homologue pairing by two-color fluorescence in situ hybridization with cosmid probes to regions on III, IX, and XI revealed that disruption of bouquet formation is associated with a significant delay (>2 h) of homologue pairing.Under naturally occurring conditions, bouquet formation may allow for rapid sporulation and confer a selective advantage.

View Article: PubMed Central - PubMed

Affiliation: Department of Human Biology and Genetics, University of Kaiserslautern, D-67653 Kaiserslautern, Germany.

ABSTRACT
We have investigated the requirements for NDJ1 in meiotic telomere redistribution and clustering in synchronized cultures of Saccharomyces cerevisiae. On induction of wild-type meiosis, telomeres disperse from premeiotic aggregates over the nuclear periphery, and then cluster near the spindle pole body (bouquet arrangement) before dispersing again. In ndj1Delta meiocytes, telomeres are scattered throughout the nucleus and fail to form perinuclear meiosis-specific distribution patterns, suggesting that Ndj1p may function to tether meiotic telomeres to the nuclear periphery. Since ndj1Delta meiocytes fail to cluster their telomeres at any prophase stage, Ndj1p is the first protein shown to be required for bouquet formation in a synaptic organism. Analysis of homologue pairing by two-color fluorescence in situ hybridization with cosmid probes to regions on III, IX, and XI revealed that disruption of bouquet formation is associated with a significant delay (>2 h) of homologue pairing. An increased and persistent fraction of ndj1Delta meiocytes with Zip1p polycomplexes suggests that chromosome polarization is important for synapsis progression. Thus, our observations support the hypothesis that meiotic telomere clustering contributes to efficient homologue alignment and synaptic pairing. Under naturally occurring conditions, bouquet formation may allow for rapid sporulation and confer a selective advantage.

Show MeSH
Related in: MedlinePlus