Structure and function of spermatocyte nucleolus in the meiotic prophase; electron microscopic and molecular anatomical analysis

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K07246
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 48010:Anatomy-related
• Research Institution: Nagasaki University
• Principal Investigator: Koji Takehiko 長崎大学, 医歯薬学総合研究科(医学系), 客員研究員 (30170179)
• Co-Investigator(Kenkyū-buntansha): 柴田 恭明 長崎大学, 医歯薬学総合研究科(医学系), 准教授 (80253673) ; 末松 貴史 長崎大学, 医歯薬学総合研究科(医学系), 技術職員 (70264249)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: マウス / 精巣 / DNAメチル化 / 5-aza-2’-deoxycitidine / 核小体 / 精祖細胞 / 精母細胞 / セルトリ細胞

Outline of Final Research Achievements

The nucleoli of spermatocytes are very unique and partially maintained during prophase of meiosis, while that of round spermatid is conspicuous but without rRNA localization. For better understanding of structure and function of the nucleoli, we conducted molecular histochemical analyses of the expression of rRNA in normal and DNA methylation inhibitor, 5-aza-2’-deoxycytidine (5-azadC) treated adult mouse testes. As a result, the transcription activity of rRNA in the nucleoli of round spermatids was suppressed because of high level of methylation of rDNA, in consistent with no nucleolin spots. The decrease in the level of DNA methylation by 5-azadC increased the number of nucleoli as well as nucleolin spots in spermatocytes. These results indicate that the states of spermatogenic cell nucleoli are regulated epigenetically by DNA methylation level of rDNA, which is progressively increased during mouse spermatogenesis.

Free Research Field

解剖学

Academic Significance and Societal Importance of the Research Achievements

核小体は核膜周囲と連なるヘテロクロマチンに囲まれ、クロマチン凝集の起点として、また染色体領域を決める核内極性の基軸として働く可能性が指摘されているが、その形成過程の詳細は不明である。本研究では精子形成過程における核小体の不活化がDNAメチル化によって誘導されることを明らかにした。人為的rRNA 転写制御は、核小体形成過程の解明や、がん悪性度の指標となる核小体数の増加機序の解明に寄与すると期待される。