Investigating the function and transgenerational effects of sperm-retained histones

Research Project

Project/Area Number	18H02369
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Review Section	Basic Section 43010:Molecular biology-related
Research Institution	The University of Tokyo
Principal Investigator	Okada Yuki 東京大学, 定量生命科学研究所, 教授 (60546430)
Project Period (FY)	2018-04-01 – 2023-03-31
Project Status	Completed (Fiscal Year 2022)
Budget Amount *help	¥15,860,000 (Direct Cost: ¥12,200,000、Indirect Cost: ¥3,660,000) Fiscal Year 2022: ¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000) Fiscal Year 2021: ¥2,600,000 (Direct Cost: ¥2,000,000、Indirect Cost: ¥600,000) Fiscal Year 2020: ¥3,250,000 (Direct Cost: ¥2,500,000、Indirect Cost: ¥750,000) Fiscal Year 2019: ¥2,990,000 (Direct Cost: ¥2,300,000、Indirect Cost: ¥690,000) Fiscal Year 2018: ¥4,550,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥1,050,000)
Keywords	精子残存ヒストン / 切断型ヒストン / 精巣特異的ヒストン / 性染色体不活化 / 精子形成 / クロマチン / 精子クロマチン / 経世代効果 / XY body / 精子 / エピゲノム / 精子特異的ヒストン切断 / 精子ヒストン
Outline of Final Research Achievements	This study aimed to clarify the nature of cleaved histone H3, which is abundantly observed in testicular germ cells, and its transgenerational effects. We found that at least two types of cleaved histone H3s exist in the germ cell differentiation-dependent manner, and one of them was cleaved at the Ala21-Thr22 of the N-terminal tail (designated as csH3). The csH3 was cleaved by cathepsin L (CTSL) in the testis, and it accumulated in the XY body of the spermatocytes, which occurred downstream of the DNA damage response. To test its transgenerational effect by ICSI, we attempted to induce differentiation of spermatocytes without csH3 to spermatids but failed to obtain spermatids due to the impaired differentiation. This study has provided insight into the presence and ontogeny of cleaved histones in spermatogenesis, their subcellular localization, cleaving enzymes, and signaling pathways upstream of cleavage.
Academic Significance and Societal Importance of the Research Achievements	本研究は、哺乳類精子形成におけるAla21-Thr22切断型H3（csH3）の存在と、DNA損傷応答との関連、さらにはその責任酵素を同定した示した初めての例である。XY bodyにはDNA損傷応答因子に加えて様々なエピゲノム修飾が集積しており、その転写状態は複雑に制御されている。本研究成果は、ヒストンテイル切断によるエピゲノム制御がそこに関与する可能性を強く示唆しており、雄性生殖細胞分化におけるエピジェネティック制御機構にヒストン切断という新たな因子を加えるものである。さらに今後実験手技を改良することによって、切断型ヒストンの経世代効果にも迫れると期待される。