Sakai Yasuhiro, Suetake Isao, Shinozaki Fuminori, Yamashina Shohei, Tajima Shoji
Department of Anatomy, Kitasato University School of Medicine, Sagamihara 228-8555, Japan.
Gene Expr Patterns. 2004 Dec;5(2):231-7. doi: 10.1016/j.modgep.2004.07.011.
In mouse male germ cells, global DNA methylation occurs in gonocytes at 16-18 days postcoitum. In the present study, we examined which de novo-type DNA methyltransferase, Dnmt3a, Dnmt3a2 or Dnmt3b is expressed in gonocytes at these stages. Immuno-histochemical and Western blot analyses revealed that Dnmt3a2 was the major DNA methyltransferase expressed in gonocytes at 14-18 day postcoitum. Dnmt3L, which is necessary for spermatogenesis, was co-expressed in gonocytes at identical stages to Dnmt3a2. On the other hand, Dnmt3a was expressed not in germ cells but in the Sertoli cells and connective tissue cells that surround gonocytes and spermatogonia. Dnmt3b2, an isoform of Dnmt3b, was expressed faintly but significantly in gonocytes at 16 days postcoitum, and increased in spermatogonia at 4 and 6 days postpartum. The expression of Dnmt3a2, Dnmt3L, and Dnmt3b2 at 14-18 dpc was confirmed by reverse transcriptase-coupled polymerase chain reaction amplification and nucleotide sequencing of the amplified fragments. The results strongly suggest that Dnmt3a2 and Dnmt3L are responsible for the global DNA methylation in mouse male germ cells.
在小鼠雄性生殖细胞中，全基因组DNA甲基化发生在合子后16 - 18天的生殖母细胞中。在本研究中，我们检测了在这些阶段的生殖母细胞中，哪种从头型DNA甲基转移酶，即Dnmt3a、Dnmt3a2或Dnmt3b会表达。免疫组织化学和蛋白质印迹分析表明，Dnmt3a2是在合子后14 - 18天的生殖母细胞中表达的主要DNA甲基转移酶。精子发生所必需的Dnmt3L在与Dnmt3a2相同的阶段在生殖母细胞中共同表达。另一方面，Dnmt3a并非在生殖细胞中表达，而是在围绕生殖母细胞和精原细胞的支持细胞和结缔组织细胞中表达。Dnmt3b的一种同工型Dnmt3b2在合子后16天的生殖母细胞中表达微弱但显著，并在产后4天和6天的精原细胞中增加。通过逆转录 - 聚合酶链反应扩增及对扩增片段的核苷酸测序，证实了Dnmt3a2、Dnmt3L和Dnmt3b2在14 - 18天胚龄时的表达。结果强烈表明，Dnmt3a2和Dnmt3L负责小鼠雄性生殖细胞中的全基因组DNA甲基化。
