title: An epigenetic switch is crucial for spermatogonia to exit the undifferentiated state toward a Kit-positive identity.
abstract: Epigenetic modifications influence gene expression and chromatin remodeling. In embryonic pluripotent stem cells, these epigenetic modifications have been extensively characterized; by contrast, the epigenetic events of tissue-specific stem cells are poorly understood. Here, we define a new epigenetic shift that is crucial for differentiation of murine spermatogonia toward meiosis. We have exploited a property of incomplete cytokinesis, which causes male germ cells to form aligned chains of characteristic lengths, as they divide and differentiate. These chains revealed the stage of spermatogenesis, so the epigenetic differences of various stages could be characterized. Single, paired and medium chain-length spermatogonia not expressing Kit (a marker of differentiating spermatogonia) showed no expression of Dnmt3a2 and Dnmt3b (two de novo DNA methyltransferases); they also lacked the transcriptionally repressive histone modification H3K9me2. By contrast, spermatogonia consisting of ~8-16 chained cells with Kit expression dramatically upregulated Dnmt3a2/3b expression and also displayed increased H3K9me2 modification. To explore the function of these epigenetic changes in spermatogonia in vivo, the DNA methylation machinery was destabilized by ectopic Dnmt3b expression or Np95 ablation. Forced Dnmt3b expression induced expression of Kit; whereas ablation of Np95, which is essential for maintaining DNA methylation, interfered with differentiation and viability only after spermatogonia become Kit positive. These data suggest that the epigenetic status of spermatogonia shifts dramatically during the Kit-negative to Kit-positive transition. This shift might serve as a switch that determines whether spermatogonia self-renew or differentiate.
authors.affiliation: Department of Histology and Cell Biology, Yokohama City University School of Medicine, Yokohama, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Shirakawa
authors.forename: Ruken
authors.initials: R
authors.lastname: Yaman-Deveci
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Tomizawa
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Kamizato
authors.forename: Kuniko
authors.initials: K
authors.lastname: Nakajima
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Sone
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Sato
authors.forename: Jafar
authors.initials: J
authors.lastname: Sharif
authors.forename: Akio
authors.initials: A
authors.lastname: Yamashita
authors.forename: Yuki
authors.initials: Y
authors.lastname: Takada-Horisawa
authors.forename: Shosei
authors.initials: S
authors.lastname: Yoshida
authors.forename: Kiyoe
authors.initials: K
authors.lastname: Ura
authors.forename: Masahiro
authors.initials: M
authors.lastname: Muto
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Koseki
authors.forename: Toshio
authors.initials: T
authors.lastname: Suda
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Ohbo
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002454:Cell Differentiation / Q000502:physiology*; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism; D019175:DNA Methylation / Q000502:physiology; D017931:DNA Primers / Q000235:genetics; D044127:Epigenesis, Genetic / Q000502:physiology*; D005434:Flow Cytometry; D005854:Germ Cells / Q000502:physiology*; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013091:Spermatogenesis / Q000502:physiology*; D013093:Spermatogonia / Q000166:cytology / Q000254:growth & development*; D000097584:DNA Methyltransferase 3B
chemical_list: D004248:DNA (Cytosine-5-)-Methyltransferases; D017931:DNA Primers; D019009:Proto-Oncogene Proteins c-kit; D000097584:DNA Methyltransferase 3B
keywords: Epigenetics; Germ cells; Kit-negative identity; Kit-positive identity; Stem cell differentiation