Int J Biol Sci 2022; 18(11):4513-4531. doi:10.7150/ijbs.75298 This issue

Research Paper

Maternal EHMT2 is essential for homologous chromosome segregation by regulating Cyclin B3 transcription in oocyte meiosis

Tie-Gang Meng1,2#, Wen-Long Lei2#, Xukun Lu3,4#, Xiao-Yu Liu5#, Xue-Shan Ma6, Xiao-Qing Nie2, Zheng-Hui Zhao2,7, Qian-Nan Li1,2, Lin Huang8, Yi Hou2, Ying-Chun Ouyang2, Lei Li2, Tie-Shan Tang9, Heide Schatten10, Wei Xie3,4, Shao-Rong Gao5, Xiang-Hong Ou1✉, Zhen-Bo Wang2,7✉, Qing-Yuan Sun1,2✉

1. Fertility Preservation Lab, Guangdong-Hong Kong Metabolism & Reproduction Joint Laboratory, Reproductive Medicine Center, Guangdong Second Provincial General Hospital, Guangzhou, 510317, China.
2. State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
3. Tsinghua-Peking Center for Life Sciences, Beijing 100084, China.
4. Center for Stem Cell Biology and Regenerative Medicine, MOE Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing 100084, China.
5. Institute for Regenerative Medicine, Shanghai East Hospital, Shanghai Key Laboratory of Signaling and Disease Research, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, 200120, China.
6. The Affiliated Tai'an City Central Hospital of Qingdao University, Taian, Shandong, 271000, China.
7. University of Chinese Academy of Sciences, Beijing 100101, China.
8. Center for Clinical Medicine Research, The Affiliated Hospital of Southwest Medical University, Luzhou 6460000, China.
9. State Key Laboratory of Membrane Biology, Institute of Zoology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, China.
10. Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA.
#These authors contributed equally to this work.

This is an open access article distributed under the terms of the Creative Commons Attribution License ( See for full terms and conditions.
Meng TG, Lei WL, Lu X, Liu XY, Ma XS, Nie XQ, Zhao ZH, Li QN, Huang L, Hou Y, Ouyang YC, Li L, Tang TS, Schatten H, Xie W, Gao SR, Ou XH, Wang ZB, Sun QY. Maternal EHMT2 is essential for homologous chromosome segregation by regulating Cyclin B3 transcription in oocyte meiosis. Int J Biol Sci 2022; 18(11):4513-4531. doi:10.7150/ijbs.75298. Available from

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Graphic abstract

During oocyte growth, various epigenetic modifications are gradually established, accompanied by accumulation of large amounts of mRNAs and proteins. However, little is known about the relationship between epigenetic modifications and meiotic progression. Here, by using Gdf9-Cre to achieve oocyte-specific ablation of Ehmt2 (Euchromatic-Histone-Lysine-Methyltransferase 2) from the primordial follicle stage, we found that female mutant mice were infertile. Oocyte-specific knockout of Ehmt2 caused failure of homologous chromosome separation independent of persistently activated SAC during the first meiosis. Further studies revealed that lacking maternal Ehmt2 affected the transcriptional level of Ccnb3, while microinjection of exogenous Ccnb3 mRNA could partly rescue the failure of homologous chromosome segregation. Of particular importance was that EHMT2 regulated ccnb3 transcriptions by regulating CTCF binding near ccnb3 gene body in genome in oocytes. In addition, the mRNA level of Ccnb3 significantly decreased in the follicles microinjected with Ctcf siRNA. Therefore, our findings highlight the novel function of maternal EHMT2 on the metaphase I-to-anaphase I transition in mouse oocytes: regulating the transcription of Ccnb3.

Keywords: EHMT2/G9a, Cyclin B3, transcriptional regulation, oocyte, meiosis, homologous chromosome segregation, CTCF