Limits...
A yeast two-hybrid screen for SYP-3 interactors identifies SYP-4, a component required for synaptonemal complex assembly and chiasma formation in Caenorhabditis elegans meiosis.

Smolikov S, Schild-Prüfert K, Colaiácovo MP - PLoS Genet. (2009)

Bottom Line: SYP-4 is essential for the localization of SYP-1, SYP-2, and SYP-3 CR proteins onto chromosomes, thereby playing a crucial role in the stabilization of pairing interactions between homologous chromosomes.The lack of chiasmata observed in syp-4 mutants supports the elevated levels of chromosome nondisjunction manifested in high embryonic lethality.Altogether our findings place SYP-4 as a central player in SC formation and broaden our understanding of the structure of the SC and its assembly.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America.

ABSTRACT
The proper assembly of the synaptonemal complex (SC) between homologs is critical to ensure accurate meiotic chromosome segregation. The SC is a meiotic tripartite structure present from yeast to humans, comprised of proteins assembled along the axes of the chromosomes and central region (CR) proteins that bridge the two chromosome axes. Here we identify SYP-4 as a novel structural component of the SC in Caenorhabditis elegans. SYP-4 interacts in a yeast two-hybrid assay with SYP-3, one of components of the CR of the SC, and is localized at the interface between homologs during meiosis. SYP-4 is essential for the localization of SYP-1, SYP-2, and SYP-3 CR proteins onto chromosomes, thereby playing a crucial role in the stabilization of pairing interactions between homologous chromosomes. In the absence of SYP-4, the levels of recombination intermediates, as indicated by RAD-51 foci, are elevated in mid-prophase nuclei, and crossover recombination events are significantly reduced. The lack of chiasmata observed in syp-4 mutants supports the elevated levels of chromosome nondisjunction manifested in high embryonic lethality. Altogether our findings place SYP-4 as a central player in SC formation and broaden our understanding of the structure of the SC and its assembly.

Show MeSH

Related in: MedlinePlus

SYP-4 localizes to chromosomes during prophase I, and its localization requires both axis-associated and CR proteins.(A–C) High magnification images of nuclei stained with DAPI and anti-SYP-4. Wild type nuclei at transition zone (A), late pachytene (B), and diakinesis (C), showing immunolocalization of SYP-4 on chromosomes throughout meiotic prophase I. Arrow in (A) indicates a premeiotic nucleus adjacent to the meiotic transition zone nuclei. Arrow in (C) indicates two superimposed bivalents. Inset in (C) indicates a single bivalent at high magnification, co-immunostained with SYP-4 (red) and HTP-3 (green). SYP-4 localizes to the region distal to the chiasma (short arms of the bivalent). (D) Pachytene nuclei exemplifying the lack of SYP-4 immunolocalization on chromosomes observed in syp-4 mutants. (E–G) SYP-4 is excluded only from unsynapsed chromosomes (arrows) observed in him-8 mutants. (H–K) SYP-4 localization in pachytene nuclei is perturbed in him-3 (H), syp-1 (I), syp-2 (J), and syp-3 (K) mutants, indicating that SYP-4 localization requires both normal axis-morphogenesis and the presence of central region proteins. Bars, 2 µm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2742731&req=5

pgen-1000669-g003: SYP-4 localizes to chromosomes during prophase I, and its localization requires both axis-associated and CR proteins.(A–C) High magnification images of nuclei stained with DAPI and anti-SYP-4. Wild type nuclei at transition zone (A), late pachytene (B), and diakinesis (C), showing immunolocalization of SYP-4 on chromosomes throughout meiotic prophase I. Arrow in (A) indicates a premeiotic nucleus adjacent to the meiotic transition zone nuclei. Arrow in (C) indicates two superimposed bivalents. Inset in (C) indicates a single bivalent at high magnification, co-immunostained with SYP-4 (red) and HTP-3 (green). SYP-4 localizes to the region distal to the chiasma (short arms of the bivalent). (D) Pachytene nuclei exemplifying the lack of SYP-4 immunolocalization on chromosomes observed in syp-4 mutants. (E–G) SYP-4 is excluded only from unsynapsed chromosomes (arrows) observed in him-8 mutants. (H–K) SYP-4 localization in pachytene nuclei is perturbed in him-3 (H), syp-1 (I), syp-2 (J), and syp-3 (K) mutants, indicating that SYP-4 localization requires both normal axis-morphogenesis and the presence of central region proteins. Bars, 2 µm.

Mentions: To examine the immunolocalization of SYP-4 on whole mounted germlines, an α-SYP-4 antibody was raised against the N-terminus (first 27 amino acids) of SYP-4. The specificity of this antibody was confirmed by detecting the presence of SYP-4 signal on meiotic chromosomes in wild type nuclei (Figure 3A–3C) and not in syp-4(tm2713) mutants (Figure 3D). In wild type, SYP-4 was first detected upon entrance into meiosis as foci or short tracks on chromosomes in transition zone nuclei (Figure 3A). SYP-4 remained associated with chromosomes throughout pachytene where it was observed between synapsed chromosomes (Figure 3B) [2],[13],[14],[26],[27]. During the transition from late pachytene into diplotene, the SC starts to disassemble and chromosome remodeling unfolds around the crossover site [28]–[30]. At this transition, SYP-4 signal was greatly reduced throughout most of the length of the chromosomes, becoming mostly concentrated towards one end of each chromosome. This asymmetric localization pattern is similar to that observed for the other SYP proteins during this transition [28]. Given that a single crossover (obligate crossover) is formed between each pair of homologous chromosomes in C. elegans [31] and this crossover is off-center, chromosome remodeling then results in bivalents at diakinesis with a cross-shaped configuration composed of a long and a short axes intersecting at the chiasma [28]. By early diakinesis, SYP-4 localization was restricted to the short axes (short arms; the region distal to the chiasma) (Figure 3C), and by the end of diakinesis it was no longer detectable on chromosomes. This distinct pattern of localization is unique to SC central region proteins, as lateral element proteins remain on both arms of the bivalent through the end of diakinesis [2],[13],[14],[26],[27].


A yeast two-hybrid screen for SYP-3 interactors identifies SYP-4, a component required for synaptonemal complex assembly and chiasma formation in Caenorhabditis elegans meiosis.

Smolikov S, Schild-Prüfert K, Colaiácovo MP - PLoS Genet. (2009)

SYP-4 localizes to chromosomes during prophase I, and its localization requires both axis-associated and CR proteins.(A–C) High magnification images of nuclei stained with DAPI and anti-SYP-4. Wild type nuclei at transition zone (A), late pachytene (B), and diakinesis (C), showing immunolocalization of SYP-4 on chromosomes throughout meiotic prophase I. Arrow in (A) indicates a premeiotic nucleus adjacent to the meiotic transition zone nuclei. Arrow in (C) indicates two superimposed bivalents. Inset in (C) indicates a single bivalent at high magnification, co-immunostained with SYP-4 (red) and HTP-3 (green). SYP-4 localizes to the region distal to the chiasma (short arms of the bivalent). (D) Pachytene nuclei exemplifying the lack of SYP-4 immunolocalization on chromosomes observed in syp-4 mutants. (E–G) SYP-4 is excluded only from unsynapsed chromosomes (arrows) observed in him-8 mutants. (H–K) SYP-4 localization in pachytene nuclei is perturbed in him-3 (H), syp-1 (I), syp-2 (J), and syp-3 (K) mutants, indicating that SYP-4 localization requires both normal axis-morphogenesis and the presence of central region proteins. Bars, 2 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2742731&req=5

pgen-1000669-g003: SYP-4 localizes to chromosomes during prophase I, and its localization requires both axis-associated and CR proteins.(A–C) High magnification images of nuclei stained with DAPI and anti-SYP-4. Wild type nuclei at transition zone (A), late pachytene (B), and diakinesis (C), showing immunolocalization of SYP-4 on chromosomes throughout meiotic prophase I. Arrow in (A) indicates a premeiotic nucleus adjacent to the meiotic transition zone nuclei. Arrow in (C) indicates two superimposed bivalents. Inset in (C) indicates a single bivalent at high magnification, co-immunostained with SYP-4 (red) and HTP-3 (green). SYP-4 localizes to the region distal to the chiasma (short arms of the bivalent). (D) Pachytene nuclei exemplifying the lack of SYP-4 immunolocalization on chromosomes observed in syp-4 mutants. (E–G) SYP-4 is excluded only from unsynapsed chromosomes (arrows) observed in him-8 mutants. (H–K) SYP-4 localization in pachytene nuclei is perturbed in him-3 (H), syp-1 (I), syp-2 (J), and syp-3 (K) mutants, indicating that SYP-4 localization requires both normal axis-morphogenesis and the presence of central region proteins. Bars, 2 µm.
Mentions: To examine the immunolocalization of SYP-4 on whole mounted germlines, an α-SYP-4 antibody was raised against the N-terminus (first 27 amino acids) of SYP-4. The specificity of this antibody was confirmed by detecting the presence of SYP-4 signal on meiotic chromosomes in wild type nuclei (Figure 3A–3C) and not in syp-4(tm2713) mutants (Figure 3D). In wild type, SYP-4 was first detected upon entrance into meiosis as foci or short tracks on chromosomes in transition zone nuclei (Figure 3A). SYP-4 remained associated with chromosomes throughout pachytene where it was observed between synapsed chromosomes (Figure 3B) [2],[13],[14],[26],[27]. During the transition from late pachytene into diplotene, the SC starts to disassemble and chromosome remodeling unfolds around the crossover site [28]–[30]. At this transition, SYP-4 signal was greatly reduced throughout most of the length of the chromosomes, becoming mostly concentrated towards one end of each chromosome. This asymmetric localization pattern is similar to that observed for the other SYP proteins during this transition [28]. Given that a single crossover (obligate crossover) is formed between each pair of homologous chromosomes in C. elegans [31] and this crossover is off-center, chromosome remodeling then results in bivalents at diakinesis with a cross-shaped configuration composed of a long and a short axes intersecting at the chiasma [28]. By early diakinesis, SYP-4 localization was restricted to the short axes (short arms; the region distal to the chiasma) (Figure 3C), and by the end of diakinesis it was no longer detectable on chromosomes. This distinct pattern of localization is unique to SC central region proteins, as lateral element proteins remain on both arms of the bivalent through the end of diakinesis [2],[13],[14],[26],[27].

Bottom Line: SYP-4 is essential for the localization of SYP-1, SYP-2, and SYP-3 CR proteins onto chromosomes, thereby playing a crucial role in the stabilization of pairing interactions between homologous chromosomes.The lack of chiasmata observed in syp-4 mutants supports the elevated levels of chromosome nondisjunction manifested in high embryonic lethality.Altogether our findings place SYP-4 as a central player in SC formation and broaden our understanding of the structure of the SC and its assembly.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America.

ABSTRACT
The proper assembly of the synaptonemal complex (SC) between homologs is critical to ensure accurate meiotic chromosome segregation. The SC is a meiotic tripartite structure present from yeast to humans, comprised of proteins assembled along the axes of the chromosomes and central region (CR) proteins that bridge the two chromosome axes. Here we identify SYP-4 as a novel structural component of the SC in Caenorhabditis elegans. SYP-4 interacts in a yeast two-hybrid assay with SYP-3, one of components of the CR of the SC, and is localized at the interface between homologs during meiosis. SYP-4 is essential for the localization of SYP-1, SYP-2, and SYP-3 CR proteins onto chromosomes, thereby playing a crucial role in the stabilization of pairing interactions between homologous chromosomes. In the absence of SYP-4, the levels of recombination intermediates, as indicated by RAD-51 foci, are elevated in mid-prophase nuclei, and crossover recombination events are significantly reduced. The lack of chiasmata observed in syp-4 mutants supports the elevated levels of chromosome nondisjunction manifested in high embryonic lethality. Altogether our findings place SYP-4 as a central player in SC formation and broaden our understanding of the structure of the SC and its assembly.

Show MeSH
Related in: MedlinePlus