Improving the production efficiency of mammalian haploid cells by controlling nuclear DNA density

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K19325
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 44:Biology at cellular to organismal levels, and related fields
• Research Institution: The University of Tokyo
• Principal Investigator: Ohsugi Miho 東京大学, 大学院総合文化研究科, 教授 (00332586)
• Project Period (FY): 2018-06-29 – 2021-03-31
• Keywords: マウス胚 / 一倍体 / 倍数性 / 雄性発生胚

Outline of Final Research Achievements

Mammalian haploid parthenogenetic embryos show low blastocyst developmental rate and some cells become diploid during development for unknown reasons, resulting in low haploid ES cell establishment efficiency. In this study, we hypothesized that these problems were caused by the fact that "haploid parthenogenetic embryos have only half the nuclear DNA density of diploid embryos". We established a method that induces symmetric division, instead of extremely asymmetric division or formation of the second polar body, after parthenogenetic activation. By halving the cell size, we produced haploid embryos whose nuclear DNA density is equivalent to that of diploid embryos. Although half-sized haploid embryos also showed genome duplication during the developmental process, they showed a highly efficient blastocyst developmental rate of about 70%.

Free Research Field

発生細胞生物学

Academic Significance and Societal Importance of the Research Achievements

「核内DNA密度が二倍体胚の半分しかない」という細胞生物学的な特徴がゲノムの倍化と発生率の低下を引き起こすのではないか、という当初の仮説は、ゲノム倍化については否定され二倍体化の抑制はできなかったが、発生率については大幅な向上が達成できたことから、一倍体ES細胞の樹立の効率化につながる成果となった。
さらに、従来の一倍体胚がもつ二倍体胚との2つの違いのうち、ゲノムを1セットしかもたないという倍数性の違いがゲノム倍化を引き起こし、核内DNA密度が半減していること、あるいはゲノムDNAの量と細胞質の量とのバランスの崩れが、初期胚の発生、特に最初の数回の卵割に重要である、という新規の知見を得た。