title: Silencing markers are retained on pericentric heterochromatin during murine primordial germ cell development.
abstract: In the nuclei of most mammalian cells, pericentric heterochromatin is characterized by DNA methylation, histone modifications such as H3K9me3 and H4K20me3, and specific binding proteins like heterochromatin-binding protein 1 isoforms (HP1 isoforms). Maintenance of this specialized chromatin structure is of great importance for genome integrity and for the controlled repression of the repetitive elements within the pericentric DNA sequence. Here we have studied histone modifications at pericentric heterochromatin during primordial germ cell (PGC) development using different fixation conditions and fluorescent immunohistochemical and immunocytochemical protocols.
  
  
  
  We observed that pericentric heterochromatin marks, such as H3K9me3, H4K20me3, and HP1 isoforms, were retained on pericentric heterochromatin throughout PGC development. However, the observed immunostaining patterns varied, depending on the fixation method, explaining previous findings of a general loss of pericentric heterochromatic features in PGCs. Also, in contrast to the general clustering of multiple pericentric regions and associated centromeres in DAPI-dense regions in somatic cells, the pericentric regions of PGCs were more frequently organized as individual entities. We also observed a transient enrichment of the chromatin remodeler ATRX in pericentric regions in embryonic day 11.5 (E11.5) PGCs. At this stage, a similar and low level of major satellite repeat RNA transcription was detected in both PGCs and somatic cells.
  
  
  
  These results indicate that in pericentric heterochromatin of mouse PGCs, only minor reductions in levels of some chromatin-associated proteins occur, in association with a transient increase in ATRX, between E11.5 and E13.5. These pericentric heterochromatin regions more frequently contain only a single centromere in PGCs compared to the surrounding soma, indicating a difference in overall organization, but there is no de-repression of major satellite transcription.
authors.affiliation: Department of Developmental Biology, Erasmus MC, University Medical Center, Rotterdam, The Netherlands.
authors.forename: Aristea
authors.initials: A
authors.lastname: Magaraki
authors.affiliation: Division of Reproductive Medicine, Department of Obstetrics and Gynecology, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: Godfried
authors.initials: G
authors.lastname: van der Heijden
authors.affiliation: Department of Developmental Biology, Erasmus MC, University Medical Center, Rotterdam, The Netherlands.
authors.forename: Esther
authors.initials: E
authors.lastname: Sleddens-Linkels
authors.affiliation: Division of Reproductive Medicine, Department of Obstetrics and Gynecology, Central Hospital of Karlstad, Karlstad, Värmland Sweden.
authors.forename: Leonidas
authors.initials: L
authors.lastname: Magarakis
authors.affiliation: Erasmus Optical Imaging Center, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: Wiggert A
authors.initials: WA
authors.lastname: van Cappellen
authors.affiliation: Friedrich Miescher Institute for Biomedical Research (FMI), Basel, Switzerland.|Faculty of Sciences, University of Basel, Basel, Switzerland.
authors.forename: Antoine H F M
authors.initials: AHFM
authors.lastname: Peters
authors.affiliation: Department of Developmental Biology, Erasmus MC, University Medical Center, Rotterdam, The Netherlands.
authors.forename: Joost
authors.initials: J
authors.lastname: Gribnau
authors.affiliation: Department of Developmental Biology, Erasmus MC, University Medical Center, Rotterdam, The Netherlands.
authors.forename: Willy M
authors.identifier: 0000-0002-9179-850X
authors.initials: WM
authors.lastname: Baarends
authors.affiliation: Department of Developmental Biology, Erasmus MC, University Medical Center, Rotterdam, The Netherlands.
authors.forename: Maureen
authors.initials: M
authors.lastname: Eijpe
mesh_terms: D000818:Animals; D002503:Centromere / Q000378:metabolism; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism; D004622:Embryo, Mammalian / Q000378:metabolism; D020868:Gene Silencing; D005854:Germ Cells / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D006570:Heterochromatin / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D007150:Immunohistochemistry; D051379:Mice; D008856:Microscopy, Fluorescence; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D006570:Heterochromatin; D006657:Histones; D020033:Protein Isoforms; D000090266:Chromobox Protein Homolog 5
keywords: ATRX; Centromere; H3K9me3; H4K20me3; HP1; Histone modifications; Immunochemistry; Major satellites; Pericentric heterochromatin; Primordial germ cell