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Corona is required for higher-order assembly of transverse filaments into full-length synaptonemal complex in Drosophila oocytes.

Page SL, Khetani RS, Lake CM, Nielsen RJ, Jeffress JK, Warren WD, Bickel SE, Hawley RS - PLoS Genet. (2008)

Bottom Line: These results demonstrate that CONA, which does not contain a coiled coil domain, is required for the stable 'zippering' of TFs to form the central region of the Drosophila SC.We speculate that CONA's role in SC formation may be similar to that of the mammalian CE proteins SYCE2 and TEX12.However, the observation that AE alignment and pairing occurs in Tex12 and Syce2 mutant meiocytes but not in cona oocytes suggests that the SC plays a more critical role in the stable association of homologs in Drosophila than it does in mammalian cells.

View Article: PubMed Central - PubMed

Affiliation: Comparative Genomics Centre, School of Pharmacy and Molecular Sciences, James Cook University, Townsville, Australia. scott.page@jcu.edu.au

ABSTRACT
The synaptonemal complex (SC) is an intricate structure that forms between homologous chromosomes early during the meiotic prophase, where it mediates homolog pairing interactions and promotes the formation of genetic exchanges. In Drosophila melanogaster, C(3)G protein forms the transverse filaments (TFs) of the SC. The N termini of C(3)G homodimers localize to the Central Element (CE) of the SC, while the C-termini of C(3)G connect the TFs to the chromosomes via associations with the axial elements/lateral elements (AEs/LEs) of the SC. Here, we show that the Drosophila protein Corona (CONA) co-localizes with C(3)G in a mutually dependent fashion and is required for the polymerization of C(3)G into mature thread-like structures, in the context both of paired homologous chromosomes and of C(3)G polycomplexes that lack AEs/LEs. Although AEs assemble in cona oocytes, they exhibit defects that are characteristic of c(3)G mutant oocytes, including failure of AE alignment and synapsis. These results demonstrate that CONA, which does not contain a coiled coil domain, is required for the stable 'zippering' of TFs to form the central region of the Drosophila SC. We speculate that CONA's role in SC formation may be similar to that of the mammalian CE proteins SYCE2 and TEX12. However, the observation that AE alignment and pairing occurs in Tex12 and Syce2 mutant meiocytes but not in cona oocytes suggests that the SC plays a more critical role in the stable association of homologs in Drosophila than it does in mammalian cells.

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CONA is required for the thread-like localization of C(3)G.Shown is the localization of CONA::Venus (green), C(3)G (red), and DAPI (blue) in region 2A of germaria from P{nos-GAL4::VP16}/+; P{UASP-cona::Venus}/+ ; conaf04903/+ (A, B, E, F, I, J, left) and P{nos-GAL4::VP16}/+ ; P{UASP-cona::Venus}/+ ; conaf04903 (C, D, G, H, K, L, right). The top, middle and bottom rows show pro-oocytes in which C(3)G was present but CONA::Venus was visible at very low to undetectable (A, B, C, D), moderate (mod.) (E, F, G, H), or high (I, J, K, L) levels. When one functional copy of the endogenous cona+ gene is present, the localization of C(3)G takes on a punctate to thread-like pattern (arrowheads) in very early cysts, even when CONA::Venus is not readily detected (A, B). The spotty to thread-like pattern of C(3)G accumulation observed in panel B is also observed in early region 2A in conaf04903/+ heterozygotes that lack the CONA::Venus construct, and represents an early stage (zygotene) in SC assembly (Figure S1C). When CONA::Venus is expressed in a cona homozygous mutant background and is the only functional CONA protein present, the initial localization of C(3)G resembles that of a cona mutant homozygote (C, D), with diffuse and spotty regions of C(3)G localization (arrowheads). C(3)G takes on a thread-like appearance only when CONA::Venus begins to be detected (G, H, K, L), showing that the assembly of C(3)G into a thread-like SC coincides with and requires the accumulation of CONA::Venus protein. Scale bars, 5 µm.
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pgen-1000194-g002: CONA is required for the thread-like localization of C(3)G.Shown is the localization of CONA::Venus (green), C(3)G (red), and DAPI (blue) in region 2A of germaria from P{nos-GAL4::VP16}/+; P{UASP-cona::Venus}/+ ; conaf04903/+ (A, B, E, F, I, J, left) and P{nos-GAL4::VP16}/+ ; P{UASP-cona::Venus}/+ ; conaf04903 (C, D, G, H, K, L, right). The top, middle and bottom rows show pro-oocytes in which C(3)G was present but CONA::Venus was visible at very low to undetectable (A, B, C, D), moderate (mod.) (E, F, G, H), or high (I, J, K, L) levels. When one functional copy of the endogenous cona+ gene is present, the localization of C(3)G takes on a punctate to thread-like pattern (arrowheads) in very early cysts, even when CONA::Venus is not readily detected (A, B). The spotty to thread-like pattern of C(3)G accumulation observed in panel B is also observed in early region 2A in conaf04903/+ heterozygotes that lack the CONA::Venus construct, and represents an early stage (zygotene) in SC assembly (Figure S1C). When CONA::Venus is expressed in a cona homozygous mutant background and is the only functional CONA protein present, the initial localization of C(3)G resembles that of a cona mutant homozygote (C, D), with diffuse and spotty regions of C(3)G localization (arrowheads). C(3)G takes on a thread-like appearance only when CONA::Venus begins to be detected (G, H, K, L), showing that the assembly of C(3)G into a thread-like SC coincides with and requires the accumulation of CONA::Venus protein. Scale bars, 5 µm.

Mentions: When CONA::Venus was expressed under the control of a nanos-GAL4::VP16 driver in a conaf04903 heterozygote in which wild-type CONA protein was also present, C(3)G was detected as puncta and short threads within early prophase nuclei before CONA::Venus signal was detectable (Figure 2A–B). The spotty to thread-like pattern of C(3)G accumulation observed in Figure 2B is also observed in early region 2A in conaf04903/+ heterozygotes that lack the CONA::Venus transgene, and represents an early stage (zygotene) in SC assembly in which the short threads of C(3)G are associated with endogenous CONA (Figure S1C). As the intensity of CONA::Venus staining increased during the progression of meiotic prophase, CONA::Venus assumed a thread-like staining pattern that co-localized with C(3)G (Figure 2E–F, 2I–J).


Corona is required for higher-order assembly of transverse filaments into full-length synaptonemal complex in Drosophila oocytes.

Page SL, Khetani RS, Lake CM, Nielsen RJ, Jeffress JK, Warren WD, Bickel SE, Hawley RS - PLoS Genet. (2008)

CONA is required for the thread-like localization of C(3)G.Shown is the localization of CONA::Venus (green), C(3)G (red), and DAPI (blue) in region 2A of germaria from P{nos-GAL4::VP16}/+; P{UASP-cona::Venus}/+ ; conaf04903/+ (A, B, E, F, I, J, left) and P{nos-GAL4::VP16}/+ ; P{UASP-cona::Venus}/+ ; conaf04903 (C, D, G, H, K, L, right). The top, middle and bottom rows show pro-oocytes in which C(3)G was present but CONA::Venus was visible at very low to undetectable (A, B, C, D), moderate (mod.) (E, F, G, H), or high (I, J, K, L) levels. When one functional copy of the endogenous cona+ gene is present, the localization of C(3)G takes on a punctate to thread-like pattern (arrowheads) in very early cysts, even when CONA::Venus is not readily detected (A, B). The spotty to thread-like pattern of C(3)G accumulation observed in panel B is also observed in early region 2A in conaf04903/+ heterozygotes that lack the CONA::Venus construct, and represents an early stage (zygotene) in SC assembly (Figure S1C). When CONA::Venus is expressed in a cona homozygous mutant background and is the only functional CONA protein present, the initial localization of C(3)G resembles that of a cona mutant homozygote (C, D), with diffuse and spotty regions of C(3)G localization (arrowheads). C(3)G takes on a thread-like appearance only when CONA::Venus begins to be detected (G, H, K, L), showing that the assembly of C(3)G into a thread-like SC coincides with and requires the accumulation of CONA::Venus protein. Scale bars, 5 µm.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2529403&req=5

pgen-1000194-g002: CONA is required for the thread-like localization of C(3)G.Shown is the localization of CONA::Venus (green), C(3)G (red), and DAPI (blue) in region 2A of germaria from P{nos-GAL4::VP16}/+; P{UASP-cona::Venus}/+ ; conaf04903/+ (A, B, E, F, I, J, left) and P{nos-GAL4::VP16}/+ ; P{UASP-cona::Venus}/+ ; conaf04903 (C, D, G, H, K, L, right). The top, middle and bottom rows show pro-oocytes in which C(3)G was present but CONA::Venus was visible at very low to undetectable (A, B, C, D), moderate (mod.) (E, F, G, H), or high (I, J, K, L) levels. When one functional copy of the endogenous cona+ gene is present, the localization of C(3)G takes on a punctate to thread-like pattern (arrowheads) in very early cysts, even when CONA::Venus is not readily detected (A, B). The spotty to thread-like pattern of C(3)G accumulation observed in panel B is also observed in early region 2A in conaf04903/+ heterozygotes that lack the CONA::Venus construct, and represents an early stage (zygotene) in SC assembly (Figure S1C). When CONA::Venus is expressed in a cona homozygous mutant background and is the only functional CONA protein present, the initial localization of C(3)G resembles that of a cona mutant homozygote (C, D), with diffuse and spotty regions of C(3)G localization (arrowheads). C(3)G takes on a thread-like appearance only when CONA::Venus begins to be detected (G, H, K, L), showing that the assembly of C(3)G into a thread-like SC coincides with and requires the accumulation of CONA::Venus protein. Scale bars, 5 µm.
Mentions: When CONA::Venus was expressed under the control of a nanos-GAL4::VP16 driver in a conaf04903 heterozygote in which wild-type CONA protein was also present, C(3)G was detected as puncta and short threads within early prophase nuclei before CONA::Venus signal was detectable (Figure 2A–B). The spotty to thread-like pattern of C(3)G accumulation observed in Figure 2B is also observed in early region 2A in conaf04903/+ heterozygotes that lack the CONA::Venus transgene, and represents an early stage (zygotene) in SC assembly in which the short threads of C(3)G are associated with endogenous CONA (Figure S1C). As the intensity of CONA::Venus staining increased during the progression of meiotic prophase, CONA::Venus assumed a thread-like staining pattern that co-localized with C(3)G (Figure 2E–F, 2I–J).

Bottom Line: These results demonstrate that CONA, which does not contain a coiled coil domain, is required for the stable 'zippering' of TFs to form the central region of the Drosophila SC.We speculate that CONA's role in SC formation may be similar to that of the mammalian CE proteins SYCE2 and TEX12.However, the observation that AE alignment and pairing occurs in Tex12 and Syce2 mutant meiocytes but not in cona oocytes suggests that the SC plays a more critical role in the stable association of homologs in Drosophila than it does in mammalian cells.

View Article: PubMed Central - PubMed

Affiliation: Comparative Genomics Centre, School of Pharmacy and Molecular Sciences, James Cook University, Townsville, Australia. scott.page@jcu.edu.au

ABSTRACT
The synaptonemal complex (SC) is an intricate structure that forms between homologous chromosomes early during the meiotic prophase, where it mediates homolog pairing interactions and promotes the formation of genetic exchanges. In Drosophila melanogaster, C(3)G protein forms the transverse filaments (TFs) of the SC. The N termini of C(3)G homodimers localize to the Central Element (CE) of the SC, while the C-termini of C(3)G connect the TFs to the chromosomes via associations with the axial elements/lateral elements (AEs/LEs) of the SC. Here, we show that the Drosophila protein Corona (CONA) co-localizes with C(3)G in a mutually dependent fashion and is required for the polymerization of C(3)G into mature thread-like structures, in the context both of paired homologous chromosomes and of C(3)G polycomplexes that lack AEs/LEs. Although AEs assemble in cona oocytes, they exhibit defects that are characteristic of c(3)G mutant oocytes, including failure of AE alignment and synapsis. These results demonstrate that CONA, which does not contain a coiled coil domain, is required for the stable 'zippering' of TFs to form the central region of the Drosophila SC. We speculate that CONA's role in SC formation may be similar to that of the mammalian CE proteins SYCE2 and TEX12. However, the observation that AE alignment and pairing occurs in Tex12 and Syce2 mutant meiocytes but not in cona oocytes suggests that the SC plays a more critical role in the stable association of homologs in Drosophila than it does in mammalian cells.

Show MeSH
Related in: MedlinePlus