BMI1 fine-tunes gene repression and activation to safeguard undifferentiated spermatogonia fate

Ruiqi Liu; Yonglin Peng; Wenfei Du; Yunqiang Wu; Wen Zhang; Congxia Hu; Min Liu; Xinhua Liu; Ji Wu; Jielin Sun; Xiaodong Zhao

doi:10.3389/fcell.2023.1146849

BMI1 fine-tunes gene repression and activation to safeguard undifferentiated spermatogonia fate

Front Cell Dev Biol. 2023 Apr 24:11:1146849. doi: 10.3389/fcell.2023.1146849. eCollection 2023.

Authors

Ruiqi Liu¹, Yonglin Peng¹, Wenfei Du¹, Yunqiang Wu¹, Wen Zhang², Congxia Hu¹, Min Liu³, Xinhua Liu⁴, Ji Wu⁵, Jielin Sun¹, Xiaodong Zhao¹

Affiliations

¹ Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Center for Systems Biomedicine, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
² Stem Cell Research and Translation Center, Nanjing Agricultural University, Nanjing, China.
³ Department of Integrative Medicine, Obstetrics and Gynecology Hospital, Fudan University, Shanghai, China.
⁴ Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Hangzhou Normal University, Hangzhou, China.
⁵ Bio-X Institutes, Shanghai Jiao Tong University, Shanghai, China.

Abstract

Introduction: Spermatogenesis is sustained by the homeostasis of self-renewal and differentiation of undifferentiated spermatogonia throughout life, which is regulated by transcriptional and posttranscriptional mechanisms. B cell-specific Moloney murine leukemia virus integration site 1 (BMI1), one of spermatogonial stem cell markers, is a member of Polycomb repressive complex 1 (PRC1) and important to spermatogenesis. However, the mechanistic underpinnings of how BMI1 regulates spermatogonia fate remain elusive. Methods: We knocked down BMI1 by siRNA to investigate the role of BMI1 in undifferentiated spermatogonia. Differentially expressed genes were identified by RNA-seq and used for KEGG pathway analysis. We performed ChIP-seq analysis in wild type and BMI1 knockdown cells to explore the underlying molecular mechanisms exerted by BMI1. BMI1-associated alterations in repressive histone modifications were detected via Western blotting and ChIP-seq. Furthermore, we performed mass spectrometry and Co-immunoprecipitation assays to investigate BMI1 co-factors. Finally, we demonstrated the genomic regions occupied by both BMI1 and its co-factor. Results: BMI1 is required for undifferentiated spermatogonia maintenance by both repressing and activating target genes. BMI1 preserves PI3K-Akt signaling pathway for spermatogonia proliferation. Decrease of BMI1 affects the deposition of repressive histone modifications H2AK119ub1 and H3K27me3. BMI also positively regulates H3K27ac deposited genes which are associated with proliferation. Moreover, we demonstrate that BMI1 interacts with Sal-like 4 (SALL4), the transcription factor critical for spermatogonia function, to co-regulate gene expression. Discussion: Overall, our study reveals that BMI1 safeguards undifferentiated spermatogonia fate through multi-functional roles in regulating gene expression programs of undifferentiated spermatogonia.

Keywords: BMI1; epigenetic regulation; polycomb repressive complex; spermatogenesis; undifferentiated spermatogonia.

Grants and funding

This work was supported by the National Key Research and Development Program of China (2018YFC1003501), and National Nature Science Foundation of China (81720108017).