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Leptotene/zygotene chromosome movement via the SUN/KASH protein bridge in Caenorhabditis elegans.

Baudrimont A, Penkner A, Woglar A, Machacek T, Wegrostek C, Gloggnitzer J, Fridkin A, Klein F, Gruenbaum Y, Pasierbek P, Jantsch V - PLoS Genet. (2010)

Bottom Line: Abrogation of synapsis led to a deceleration of SUN-1 aggregate movement.Analysis of matefin/SUN-1 in a double-strand break deficient mutant revealed that repair intermediates influenced matefin/SUN-1 aggregate dynamics.Investigation of movement in meiotic regulator mutants substantiated that proper orchestration of the meiotic program and effective repair of DNA double-strand breaks were necessary for the wild-type behavior of matefin/SUN-1 aggregates.

View Article: PubMed Central - PubMed

Affiliation: Department of Chromosome Biology, Max F. Perutz Laboratories, University of Vienna, Vienna, Austria.

ABSTRACT
The Caenorhabditis elegans inner nuclear envelope protein matefin/SUN-1 plays a conserved, pivotal role in the process of genome haploidization. CHK-2-dependent phosphorylation of SUN-1 regulates homologous chromosome pairing and interhomolog recombination in Caenorhabditis elegans. Using time-lapse microscopy, we characterized the movement of matefin/SUN-1::GFP aggregates (the equivalent of chromosomal attachment plaques) and showed that the dynamics of matefin/SUN-1 aggregates remained unchanged throughout leptonene/zygotene, despite the progression of pairing. Movement of SUN-1 aggregates correlated with chromatin polarization. We also analyzed the requirements for the formation of movement-competent matefin/SUN-1 aggregates in the context of chromosome structure and found that chromosome axes were required to produce wild-type numbers of attachment plaques. Abrogation of synapsis led to a deceleration of SUN-1 aggregate movement. Analysis of matefin/SUN-1 in a double-strand break deficient mutant revealed that repair intermediates influenced matefin/SUN-1 aggregate dynamics. Investigation of movement in meiotic regulator mutants substantiated that proper orchestration of the meiotic program and effective repair of DNA double-strand breaks were necessary for the wild-type behavior of matefin/SUN-1 aggregates.

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Impact of SC components on the dynamics of SUN-1 aggregates.him-3(gk149) (A), htp-1(gk174) (B), syp-2(ok307) (C), and syp-3(me42) (D), with projection of cumulative movement (i), displacement tracks (ii), and distribution of the projected speed (iii). Arcs represent traveled distance (iv). Blue lines represent values from the first movie, orange lines from the second. (C) syp-2(ok307) (i), (ii), (iii), and (iv) from the distal part of the extended TZ and i', ii', iii', and iv' from the proximal part. See Table 1 for number of nuclei analyzed. Scale bar: 2 µm.
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pgen-1001219-g004: Impact of SC components on the dynamics of SUN-1 aggregates.him-3(gk149) (A), htp-1(gk174) (B), syp-2(ok307) (C), and syp-3(me42) (D), with projection of cumulative movement (i), displacement tracks (ii), and distribution of the projected speed (iii). Arcs represent traveled distance (iv). Blue lines represent values from the first movie, orange lines from the second. (C) syp-2(ok307) (i), (ii), (iii), and (iv) from the distal part of the extended TZ and i', ii', iii', and iv' from the proximal part. See Table 1 for number of nuclei analyzed. Scale bar: 2 µm.

Mentions: The him-3(gk149) allele displays loss of the polarized conformation of chromatin in the TZ of the gonad and lacks presynaptic alignment [40]. Depleting HIM-3 resulted in 1.1±0.3 (SD, n = 53) SUN-1 aggregates moving inside a nucleus (Table 1), and, on rare occasions, up to two aggregates (Figure 4Ai and 4Aii) unable to fuse (Figure 2A, Video S4). The projected speed distribution of the aggregates was “Gaussian-shaped,” with 95% of the aggregates moving within a range of 10–100 nm/s (Figure 4Aiii); this was significantly reduced compared to wild type (Mann-Whitney test, p<0.001). Depletion of HIM-3 also reduced the distance traveled by the SUN-1 aggregates: arc values only varied between 23° and 91° (Figure 4Aiv). HIM-8 is one of the four PC proteins, and binds specifically to the X chromosome [25]. In him-3(gk149), HIM-8 always colocalizes with SUN-1::GFP, as shown by immunostaining [28]. Thus, the single SUN-1 aggregate moving with a reduced projected speed corresponds to the X chromosome and HIM-3 is, therefore, required for the formation of autosomal chromosome attachment plaques ([28] and this study). To test whether the formation of SUN-1 aggregates was impaired in him-3(gk149) due to mislocalization of the PC proteins, we stained him-3(gk149) with the PC protein ZIM-3 (marker for chromosomes I and IV). In him-3(gk149) mutant worms, the PC protein ZIM-3 did not colocalize with SUN-1 aggregates, although chromatin-associated signals were observed (Figure S4, Text S2). Therefore, we hypothesize that defective lateral elements of the SC impeded functional attachment plaque formation.


Leptotene/zygotene chromosome movement via the SUN/KASH protein bridge in Caenorhabditis elegans.

Baudrimont A, Penkner A, Woglar A, Machacek T, Wegrostek C, Gloggnitzer J, Fridkin A, Klein F, Gruenbaum Y, Pasierbek P, Jantsch V - PLoS Genet. (2010)

Impact of SC components on the dynamics of SUN-1 aggregates.him-3(gk149) (A), htp-1(gk174) (B), syp-2(ok307) (C), and syp-3(me42) (D), with projection of cumulative movement (i), displacement tracks (ii), and distribution of the projected speed (iii). Arcs represent traveled distance (iv). Blue lines represent values from the first movie, orange lines from the second. (C) syp-2(ok307) (i), (ii), (iii), and (iv) from the distal part of the extended TZ and i', ii', iii', and iv' from the proximal part. See Table 1 for number of nuclei analyzed. Scale bar: 2 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2991264&req=5

pgen-1001219-g004: Impact of SC components on the dynamics of SUN-1 aggregates.him-3(gk149) (A), htp-1(gk174) (B), syp-2(ok307) (C), and syp-3(me42) (D), with projection of cumulative movement (i), displacement tracks (ii), and distribution of the projected speed (iii). Arcs represent traveled distance (iv). Blue lines represent values from the first movie, orange lines from the second. (C) syp-2(ok307) (i), (ii), (iii), and (iv) from the distal part of the extended TZ and i', ii', iii', and iv' from the proximal part. See Table 1 for number of nuclei analyzed. Scale bar: 2 µm.
Mentions: The him-3(gk149) allele displays loss of the polarized conformation of chromatin in the TZ of the gonad and lacks presynaptic alignment [40]. Depleting HIM-3 resulted in 1.1±0.3 (SD, n = 53) SUN-1 aggregates moving inside a nucleus (Table 1), and, on rare occasions, up to two aggregates (Figure 4Ai and 4Aii) unable to fuse (Figure 2A, Video S4). The projected speed distribution of the aggregates was “Gaussian-shaped,” with 95% of the aggregates moving within a range of 10–100 nm/s (Figure 4Aiii); this was significantly reduced compared to wild type (Mann-Whitney test, p<0.001). Depletion of HIM-3 also reduced the distance traveled by the SUN-1 aggregates: arc values only varied between 23° and 91° (Figure 4Aiv). HIM-8 is one of the four PC proteins, and binds specifically to the X chromosome [25]. In him-3(gk149), HIM-8 always colocalizes with SUN-1::GFP, as shown by immunostaining [28]. Thus, the single SUN-1 aggregate moving with a reduced projected speed corresponds to the X chromosome and HIM-3 is, therefore, required for the formation of autosomal chromosome attachment plaques ([28] and this study). To test whether the formation of SUN-1 aggregates was impaired in him-3(gk149) due to mislocalization of the PC proteins, we stained him-3(gk149) with the PC protein ZIM-3 (marker for chromosomes I and IV). In him-3(gk149) mutant worms, the PC protein ZIM-3 did not colocalize with SUN-1 aggregates, although chromatin-associated signals were observed (Figure S4, Text S2). Therefore, we hypothesize that defective lateral elements of the SC impeded functional attachment plaque formation.

Bottom Line: Abrogation of synapsis led to a deceleration of SUN-1 aggregate movement.Analysis of matefin/SUN-1 in a double-strand break deficient mutant revealed that repair intermediates influenced matefin/SUN-1 aggregate dynamics.Investigation of movement in meiotic regulator mutants substantiated that proper orchestration of the meiotic program and effective repair of DNA double-strand breaks were necessary for the wild-type behavior of matefin/SUN-1 aggregates.

View Article: PubMed Central - PubMed

Affiliation: Department of Chromosome Biology, Max F. Perutz Laboratories, University of Vienna, Vienna, Austria.

ABSTRACT
The Caenorhabditis elegans inner nuclear envelope protein matefin/SUN-1 plays a conserved, pivotal role in the process of genome haploidization. CHK-2-dependent phosphorylation of SUN-1 regulates homologous chromosome pairing and interhomolog recombination in Caenorhabditis elegans. Using time-lapse microscopy, we characterized the movement of matefin/SUN-1::GFP aggregates (the equivalent of chromosomal attachment plaques) and showed that the dynamics of matefin/SUN-1 aggregates remained unchanged throughout leptonene/zygotene, despite the progression of pairing. Movement of SUN-1 aggregates correlated with chromatin polarization. We also analyzed the requirements for the formation of movement-competent matefin/SUN-1 aggregates in the context of chromosome structure and found that chromosome axes were required to produce wild-type numbers of attachment plaques. Abrogation of synapsis led to a deceleration of SUN-1 aggregate movement. Analysis of matefin/SUN-1 in a double-strand break deficient mutant revealed that repair intermediates influenced matefin/SUN-1 aggregate dynamics. Investigation of movement in meiotic regulator mutants substantiated that proper orchestration of the meiotic program and effective repair of DNA double-strand breaks were necessary for the wild-type behavior of matefin/SUN-1 aggregates.

Show MeSH
Related in: MedlinePlus