title: Corona is required for higher-order assembly of transverse filaments into full-length synaptonemal complex in Drosophila oocytes.
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.
authors.affiliation: Comparative Genomics Centre, School of Pharmacy and Molecular Sciences, James Cook University, Townsville, Australia. scott.page@jcu.edu.au
authors.forename: Scott L
authors.initials: SL
authors.lastname: Page
authors.forename: Radhika S
authors.initials: RS
authors.lastname: Khetani
authors.forename: Cathleen M
authors.initials: CM
authors.lastname: Lake
authors.forename: Rachel J
authors.initials: RJ
authors.lastname: Nielsen
authors.forename: Jennifer K
authors.initials: JK
authors.lastname: Jeffress
authors.forename: William D
authors.initials: WD
authors.lastname: Warren
authors.forename: Sharon E
authors.initials: SE
authors.lastname: Bickel
authors.forename: R Scott
authors.initials: RS
authors.lastname: Hawley
mesh_terms: D000818:Animals; D002875:Chromosomes / Q000378:metabolism; D029721:Drosophila Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008540:Meiosis; D009865:Oocytes / Q000737:chemistry* / Q000378:metabolism*; D021381:Protein Transport; D013573:Synaptonemal Complex / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: C532574:C3G protein, Drosophila; D029721:Drosophila Proteins; C532575:cona protein, Drosophila