title: Meiosis in mice without a synaptonemal complex.
abstract: The synaptonemal complex (SC) promotes fusion of the homologous chromosomes (synapsis) and crossover recombination events during meiosis. The SC displays an extensive structural conservation between species; however, a few organisms lack SC and execute meiotic process in a SC-independent manner. To clarify the SC function in mammals, we have generated a mutant mouse strain (Sycp1(-/-)Sycp3(-/-), here called SC-null) in which all known SC proteins have been displaced from meiotic chromosomes. While transmission electron microscopy failed to identify any remnants of the SC in SC-null spermatocytes, neither formation of the cohesion axes nor attachment of the chromosomes to the nuclear membrane was perturbed. Furthermore, the meiotic chromosomes in SC-null meiocytes achieved pre-synaptic pairing, underwent early homologous recombination events and sustained a residual crossover formation. In contrast, in SC-null meiocytes synapsis and MLH1-MLH3-dependent crossovers maturation were abolished, whereas the structural integrity of chromosomes was drastically impaired. The variable consequences that SC inactivation has on the meiotic process in different organisms, together with the absence of SC in some unrelated species, imply that the SC could have originated independently in different taxonomic groups.
authors.affiliation: Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden. Anna.Kouznetsova@ki.se
authors.forename: Anna
authors.initials: A
authors.lastname: Kouznetsova
authors.forename: Ricardo
authors.initials: R
authors.lastname: Benavente
authors.forename: Albert
authors.initials: A
authors.lastname: Pastink
authors.forename: Christer
authors.initials: C
authors.lastname: Höög
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D002875:Chromosomes / Q000648:ultrastructure; D004268:DNA-Binding Proteins; D059765:Homologous Recombination; D006801:Humans; D008297:Male; D008540:Meiosis; D051379:Mice; D008817:Mice, Mutant Strains; D009687:Nuclear Proteins / Q000235:genetics; D011995:Recombination, Genetic; D013090:Spermatocytes / Q000166:cytology; D013573:Synaptonemal Complex / Q000378:metabolism; D013997:Time Factors; D000097722:Cohesins
chemical_list: D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D000097722:Cohesins; C489754:Sycp1 protein, mouse; C490062:Sycp3 protein, mouse