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SOLO: a meiotic protein required for centromere cohesion, coorientation, and SMC1 localization in Drosophila melanogaster.

Yan R, Thomas SE, Tsai JH, Yamada Y, McKee BD - J. Cell Biol. (2010)

Bottom Line: Centromeric foci of the cohesin protein SMC1 are absent in solo mutants at all meiotic stages.SOLO and SMC1 colocalize to meiotic centromeres from early prophase I until anaphase II in wild-type males, but both proteins disappear prematurely at anaphase I in mutants for mei-S332, which encodes the Drosophila homologue of the cohesin protector protein shugoshin.The solo mutant phenotypes and the localization patterns of SOLO and SMC1 indicate that they function together to maintain sister chromatid cohesion in Drosophila meiosis.

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Affiliation: Department of Biochemistry, Cellular, and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA.

ABSTRACT
Sister chromatid cohesion is essential to maintain stable connections between homologues and sister chromatids during meiosis and to establish correct centromere orientation patterns on the meiosis I and II spindles. However, the meiotic cohesion apparatus in Drosophila melanogaster remains largely uncharacterized. We describe a novel protein, sisters on the loose (SOLO), which is essential for meiotic cohesion in Drosophila. In solo mutants, sister centromeres separate before prometaphase I, disrupting meiosis I centromere orientation and causing nondisjunction of both homologous and sister chromatids. Centromeric foci of the cohesin protein SMC1 are absent in solo mutants at all meiotic stages. SOLO and SMC1 colocalize to meiotic centromeres from early prophase I until anaphase II in wild-type males, but both proteins disappear prematurely at anaphase I in mutants for mei-S332, which encodes the Drosophila homologue of the cohesin protector protein shugoshin. The solo mutant phenotypes and the localization patterns of SOLO and SMC1 indicate that they function together to maintain sister chromatid cohesion in Drosophila meiosis.

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Localization pattern of SOLO. (A) Colocalization of Venus::SOLO and CID on meiotic centromeres in WT spermatocytes. {UASp-Venus::SOLO}/{nos-GAL4::VP16}) WT males were stained with anti-CID and DAPI. (B) SOLO::Venus localizes to spermatogonia (gonia) but not somatic cyst cells in an eight-cell cyst from UPS-SOLO:Venus males. Arrows indicate cyst nuclei. Venus::SOLO and SOLO::Venus were detected by native fluorescence. S1, early prophase I; MI, metaphase I; MII, metaphase II; AII, anaphase II. Bars, 5 µm.
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fig6: Localization pattern of SOLO. (A) Colocalization of Venus::SOLO and CID on meiotic centromeres in WT spermatocytes. {UASp-Venus::SOLO}/{nos-GAL4::VP16}) WT males were stained with anti-CID and DAPI. (B) SOLO::Venus localizes to spermatogonia (gonia) but not somatic cyst cells in an eight-cell cyst from UPS-SOLO:Venus males. Arrows indicate cyst nuclei. Venus::SOLO and SOLO::Venus were detected by native fluorescence. S1, early prophase I; MI, metaphase I; MII, metaphase II; AII, anaphase II. Bars, 5 µm.

Mentions: Using nos-GAL4::VP16 to induce Venus::SOLO expression, bright Venus foci were seen in nuclei of spermatocytes of all stages up to and including metaphase II but were absent at anaphase II and subsequent stages (Fig. 6 A). Both the numbers of Venus::SOLO foci per nucleus (up to eight in primary spermatocytes and four in secondary spermatocytes) and the fact that they overlapped CID foci at all stages indicate that Venus::SOLO localizes to centromeres. In late prophase I nuclei, the centromeric Venus::SOLO foci were sometimes larger and more diffuse (Fig. S4 A, stage S6) than CID foci at similar stages (Figs. 4 and 6), suggesting that SOLO localizes to centric heterochromatic regions that are broader than the centromeres proper. A similar localization pattern was observed using a transgene containing a 2.7-kb fragment from the region immediately upstream of exon 1 of the vas/solo locus that has previously been shown to contain the vas regulatory elements (Sano et al., 2002) fused to SOLO::Venus (unpublished data). Curiously, in these males, SOLO::Venus foci are also present in nuclei of premeiotic spermatogonial cells despite the aforementioned evidence that solo is dispensable for spermatogonial chromatid segregation. However, no expression of UPS-SOLO::Venus was detected in the somatic cyst cells of testes (Fig. 6 B). Centromeric SOLO::Venus foci were also present in meiotic cells of UPS-SOLO::Venus females, which is consistent with a requirement for solo in female meiotic chromosome segregation, but were absent in somatic follicle cells (Fig. S5). Thus, SOLO appears to be germline specific but not meiosis specific in its expression pattern, although only meiotic phenotypes have been detected in solo mutants.


SOLO: a meiotic protein required for centromere cohesion, coorientation, and SMC1 localization in Drosophila melanogaster.

Yan R, Thomas SE, Tsai JH, Yamada Y, McKee BD - J. Cell Biol. (2010)

Localization pattern of SOLO. (A) Colocalization of Venus::SOLO and CID on meiotic centromeres in WT spermatocytes. {UASp-Venus::SOLO}/{nos-GAL4::VP16}) WT males were stained with anti-CID and DAPI. (B) SOLO::Venus localizes to spermatogonia (gonia) but not somatic cyst cells in an eight-cell cyst from UPS-SOLO:Venus males. Arrows indicate cyst nuclei. Venus::SOLO and SOLO::Venus were detected by native fluorescence. S1, early prophase I; MI, metaphase I; MII, metaphase II; AII, anaphase II. Bars, 5 µm.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2819681&req=5

fig6: Localization pattern of SOLO. (A) Colocalization of Venus::SOLO and CID on meiotic centromeres in WT spermatocytes. {UASp-Venus::SOLO}/{nos-GAL4::VP16}) WT males were stained with anti-CID and DAPI. (B) SOLO::Venus localizes to spermatogonia (gonia) but not somatic cyst cells in an eight-cell cyst from UPS-SOLO:Venus males. Arrows indicate cyst nuclei. Venus::SOLO and SOLO::Venus were detected by native fluorescence. S1, early prophase I; MI, metaphase I; MII, metaphase II; AII, anaphase II. Bars, 5 µm.
Mentions: Using nos-GAL4::VP16 to induce Venus::SOLO expression, bright Venus foci were seen in nuclei of spermatocytes of all stages up to and including metaphase II but were absent at anaphase II and subsequent stages (Fig. 6 A). Both the numbers of Venus::SOLO foci per nucleus (up to eight in primary spermatocytes and four in secondary spermatocytes) and the fact that they overlapped CID foci at all stages indicate that Venus::SOLO localizes to centromeres. In late prophase I nuclei, the centromeric Venus::SOLO foci were sometimes larger and more diffuse (Fig. S4 A, stage S6) than CID foci at similar stages (Figs. 4 and 6), suggesting that SOLO localizes to centric heterochromatic regions that are broader than the centromeres proper. A similar localization pattern was observed using a transgene containing a 2.7-kb fragment from the region immediately upstream of exon 1 of the vas/solo locus that has previously been shown to contain the vas regulatory elements (Sano et al., 2002) fused to SOLO::Venus (unpublished data). Curiously, in these males, SOLO::Venus foci are also present in nuclei of premeiotic spermatogonial cells despite the aforementioned evidence that solo is dispensable for spermatogonial chromatid segregation. However, no expression of UPS-SOLO::Venus was detected in the somatic cyst cells of testes (Fig. 6 B). Centromeric SOLO::Venus foci were also present in meiotic cells of UPS-SOLO::Venus females, which is consistent with a requirement for solo in female meiotic chromosome segregation, but were absent in somatic follicle cells (Fig. S5). Thus, SOLO appears to be germline specific but not meiosis specific in its expression pattern, although only meiotic phenotypes have been detected in solo mutants.

Bottom Line: Centromeric foci of the cohesin protein SMC1 are absent in solo mutants at all meiotic stages.SOLO and SMC1 colocalize to meiotic centromeres from early prophase I until anaphase II in wild-type males, but both proteins disappear prematurely at anaphase I in mutants for mei-S332, which encodes the Drosophila homologue of the cohesin protector protein shugoshin.The solo mutant phenotypes and the localization patterns of SOLO and SMC1 indicate that they function together to maintain sister chromatid cohesion in Drosophila meiosis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biochemistry, Cellular, and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA.

ABSTRACT
Sister chromatid cohesion is essential to maintain stable connections between homologues and sister chromatids during meiosis and to establish correct centromere orientation patterns on the meiosis I and II spindles. However, the meiotic cohesion apparatus in Drosophila melanogaster remains largely uncharacterized. We describe a novel protein, sisters on the loose (SOLO), which is essential for meiotic cohesion in Drosophila. In solo mutants, sister centromeres separate before prometaphase I, disrupting meiosis I centromere orientation and causing nondisjunction of both homologous and sister chromatids. Centromeric foci of the cohesin protein SMC1 are absent in solo mutants at all meiotic stages. SOLO and SMC1 colocalize to meiotic centromeres from early prophase I until anaphase II in wild-type males, but both proteins disappear prematurely at anaphase I in mutants for mei-S332, which encodes the Drosophila homologue of the cohesin protector protein shugoshin. The solo mutant phenotypes and the localization patterns of SOLO and SMC1 indicate that they function together to maintain sister chromatid cohesion in Drosophila meiosis.

Show MeSH
Related in: MedlinePlus