title: Chromosome-wide regulation of meiotic crossover formation in Caenorhabditis elegans requires properly assembled chromosome axes.
abstract: Most sexually reproducing organisms depend on the regulated formation of crossovers, and the consequent chiasmata, to accomplish successful segregation of homologous chromosomes at the meiosis I division. A robust, chromosome-wide crossover control system limits chromosome pairs to one crossover in most meioses in the nematode Caenorhabditis elegans; this system has been proposed to rely on structural integrity of meiotic chromosome axes. Here, we test this hypothesis using a mutant, him-3(me80), that assembles reduced levels of meiosis-specific axis component HIM-3 along cohesin-containing chromosome axes. Whereas pairing, synapsis, and crossing over are eliminated when HIM-3 is absent, the him-3(me80) mutant supports assembly of synaptonemal complex protein SYP-1 along some paired chromosomes, resulting in partial competence for chiasma formation. We present both genetic and cytological evidence indicating that the him-3(me80) mutation leads to an increased incidence of meiotic products with two crossovers. These results indicate that limiting the amount of a major axis component results in a reduced capacity to communicate the presence of a (nascent) crossover and/or to discourage others in response.
authors.affiliation: Department of Developmental Biology and Department of Genetics, Stanford University School of Medicine, Stanford, California 94305, USA.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Nabeshima
authors.forename: Anne M
authors.initials: AM
authors.lastname: Villeneuve
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Hillers
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000502:physiology; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000502:physiology; D023902:Chromosome Pairing / Q000502:physiology; D002875:Chromosomes / Q000502:physiology*; D003434:Crossing Over, Genetic / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D008040:Genetic Linkage; D008540:Meiosis / Q000502:physiology*; D009154:Mutation; D051135:Rad51 Recombinase; D014960:X Chromosome / Q000502:physiology
chemical_list: D029742:Caenorhabditis elegans Proteins; D004268:DNA-Binding Proteins; C121599:HIM-3 protein, C elegans; D051135:Rad51 Recombinase; C495148:rad-51 protein, C elegans