title: Superresolution imaging reveals structurally distinct periodic patterns of chromatin along pachytene chromosomes.
abstract: During meiosis, homologous chromosomes associate to form the synaptonemal complex (SC), a structure essential for fertility. Information about the epigenetic features of chromatin within this structure at the level of superresolution microscopy is largely lacking. We combined single-molecule localization microscopy (SMLM) with quantitative analytical methods to describe the epigenetic landscape of meiotic chromosomes at the pachytene stage in mouse oocytes. DNA is found to be nonrandomly distributed along the length of the SC in condensed clusters. Periodic clusters of repressive chromatin [trimethylation of histone H3 at lysine (Lys) 27 (H3K27me3)] are found at 500-nm intervals along the SC, whereas one of the ends of the SC displays a large and dense cluster of centromeric histone mark [trimethylation of histone H3 at Lys 9 (H3K9me3)]. Chromatin associated with active transcription [trimethylation of histone H3 at Lys 4 (H3K4me3)] is arranged in a radial hair-like loop pattern emerging laterally from the SC. These loops seem to be punctuated with small clusters of H3K4me3 with an average spread larger than their periodicity. Our findings indicate that the nanoscale structure of the pachytene chromosomes is constrained by periodic patterns of chromatin marks, whose function in recombination and higher order genome organization is yet to be elucidated.
authors.affiliation: Institute of Molecular Biology (IMB), 55128 Mainz, Germany; Institute for Pharmacy and Molecular Biotechnology, University of Heidelberg, 69120 Heidelberg, Germany;
authors.forename: Kirti
authors.identifier: http://orcid.org/0000-0002-0325-9988
authors.initials: K
authors.lastname: Prakash
authors.affiliation: Institute of Molecular Biology (IMB), 55128 Mainz, Germany;
authors.forename: David
authors.initials: D
authors.lastname: Fournier
authors.affiliation: Institute of Molecular Biology (IMB), 55128 Mainz, Germany;
authors.forename: Stefan
authors.initials: S
authors.lastname: Redl
authors.affiliation: Department of Molecular Spectroscopy, Max Planck Institute for Polymer Research, 55128 Mainz, Germany;
authors.forename: Gerrit
authors.initials: G
authors.lastname: Best
authors.affiliation: Institute of Molecular Biology (IMB), 55128 Mainz, Germany; Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna Biocenter Campus, 1030 Vienna, Austria.
authors.forename: Máté
authors.initials: M
authors.lastname: Borsos
authors.affiliation: Institute of Molecular Biology (IMB), 55128 Mainz, Germany;
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Tiwari
authors.affiliation: Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna Biocenter Campus, 1030 Vienna, Austria.
authors.forename: Kikuë
authors.initials: K
authors.lastname: Tachibana-Konwalski
authors.affiliation: Institute of Molecular Biology (IMB), 55128 Mainz, Germany;
authors.forename: René F
authors.initials: RF
authors.lastname: Ketting
authors.affiliation: Department of Molecular Spectroscopy, Max Planck Institute for Polymer Research, 55128 Mainz, Germany;
authors.forename: Sapun H
authors.initials: SH
authors.lastname: Parekh
authors.affiliation: Institute of Molecular Biology (IMB), 55128 Mainz, Germany; Institute for Pharmacy and Molecular Biotechnology, University of Heidelberg, 69120 Heidelberg, Germany; c.cremer@imb-mainz.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Cremer
authors.affiliation: Institute of Molecular Biology (IMB), 55128 Mainz, Germany;
authors.forename: Udo J
authors.initials: UJ
authors.lastname: Birk
mesh_terms: D000818:Animals; D002503:Centromere / Q000378:metabolism; D002843:Chromatin / Q000737:chemistry* / Q000378:metabolism*; D033481:Chromosomes, Mammalian / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D008745:Methylation; D051379:Mice; D008853:Microscopy / Q000379:methods*; D008954:Models, Biological; D049471:Pachytene Stage; D013573:Synaptonemal Complex / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D002843:Chromatin; D006657:Histones; D008239:Lysine
keywords: chromatin organization; epigenetics; histone modifications; meiosis; superresolution microscopy