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Chunsheng HAN, Ph. D.

Gene expression and regulation in spermatogenesis


Lab Manager: Mrs. Xiwen Lin, Bioinformatics Analyst, Software Engineer
Graduate Studentgs: Jian Chen, Xiangjing Hu, Yanmin Feng, Daoqin Zhang, Chunwei Zheng, Zhen Li, Longfei Ma, Yan Ning

 

  Spermatogenesis, the production of spermatozoa from a small population of stem cells named spermatogonial stem cells (SSCs), is one of the most complex developmental processes in sexually reproducing animals. During early embryonic development, a group of epiblast cells were specified as primordial germ cells (PGCc), which eventually give rise to SSCs after proliferation, migration and differentiation. SSCs not only undergo differentiation to become spermatocytes that generate haploid gamates after meiosis but also reprogram to become pluripotent stem cells in vitro. Therefore, SSCs are an excellent model for the studies of stem cell self-renewal, differentiation, reprogramming and meiosis. Defects in spermatogenesis result in not only disruptions of male fertility but also abnormal offsprings. On the other hand, artificial manipulation of spermatogenesis could lead to innovations of novel technologies for birth control, animal breeding, and restoration of male infertility and birth defects as well as for deriving novel pluripotent stem cells that can be used in regenerative medicine. We are currently focusing on studying the molecular mechanisms of SSCs proliferation, differentiation, reprogramming as well as the derivation of germ cells from pluripotent stem cells by using methods of molecular biology, mouse gene knockout, high throughput omics coupled with bioinformatics analysis.



Mammalian spermatogenesis is an ideal model for fundamental biological processes such as meiosis, stem cell self-renewal and differentiation as well as epigenetic dynamics.



In vitro propagation of mouse spermatogonial stem cells (SSCs). SSCs express marker genes of stem cells and germ cells, and can be transfected by lentivirus. SSCs recover spermatogenesis after transplantation and give birth to transgenic mice.



Induction of PGC-like cells from mouse iPSCs.



Transcriptomic profiles of mouse spermatogenic cells.

 

 

  My overall research goal is to explore the molecular mechanisms of mammalian spermatogenesis aiming to develop novel treatments for male infertility. My major scientific achievements include the following two.

1. Systematic studies of the molecular mechanisms of gene regulation in mammalian spermatogenesis. Spermatogenesis refers to the production of sperm from the spermatogonial stem cells (SSCs) through a complex cellular developmental process, which involves the generation of multiple intermediate cell types. This process is roughly divided into three sequential stages—the mitotic division of spermatogonia, the meiosis of spermatocytes, and the post-meiotic morphogenesis of spermatids. It involves the participation of a large number of genes, of which 4% are specifically expressed in spermatogenic cells, particularly during and after meiosis. I have been interested in how the expressions of these genes are regulated at the transcriptional and post-transcriptional levels. I have used several omic approaches to profile the epigenomes, the transcriptomes and the proteomes of various spermatogenic cells. I have found that the global levels of 5-methylcytosine keep constant during spermatogenesis but those of 5-hydroxymethylcytosines change dynamically and such changes correlate with the levels of various RNAs (Nature Communications 4, 1995). I have discovered five major gene regulation mechanisms in mammalian spermatogenesis by comparing the levels of proteins and mRNAs (Molecular and Cellular Proteomics, 12, 1144). I have also identified many important features of piRNA precursor (RNA 17, 1191).
2. Establishment of in vitro systems for the proliferation of mouse SSCs (mSSCs) and for the induction of primordial germ cells (PGCs). SSCs have great application potentials because they differentiate to produce sperm in vivo and de-differentiate to become pluripotent stem cells in vitro. An in vitro culture system plus genetic modifications of SSCs could lead to novel technologies for the restoration of male infertility and birth defects. I have established an in vitro system for long-term propagation and genetic manipulation of mSSCs, which, coupled with SSC transplantation, gives rise to transgenic mice. The original procedure for mSSC isolation and culture was complicated by the use of feeder cells and serum products. I have simplified the procedure greatly and improve the success rate of mSSC culture. More importantly, I have found that FGF2 is secreted by mSSC themselves, and plays an essential role for the self-renewal of mSSCs (Cell Research 22, 773).  In addition, I have also developed an in vitro system for inducing iPS cells into PGC-like cells and further into SSC-like cells (Stem Cell Research 12, 517).

I have the following two ongoing projects, the general goal of which is to develop SSC-based male infertility treatment.
1.To establish an in vitro meiosis platform and study the mechanisms of meiosis. I have been able to induce mSSCs to become spermatocytes. The two scientific objectives are to investigate how transcription factors and chromatin remodeling complex regulate the dynamic changes of the epigenome and to study how piRNAs are involved in gene regulation for the initiation and accomplishment of meiosis.
2.To induce somatic cells into germ cells and study the mechanisms of germ cell specification. I will first use germ cell-specific transcription factors to induce somatic cells into PGC-like cells or SSC-like cells. Then, I will try to screen small molecules that can replace the transcription factors. I will identify genes and pathways activated by these transcription factors and small molecules.

 

Selected publications:

  1. Chen, J., Cai, T., Zheng, C., Lin, X., Wang, G., Liao, S., Wang, X., Gan, H., Zhang, D., Hu, X., Wang, S., Li, Z., Feng, Y., Yang, F., and Han, C. (2016) MicroRNA-202 maintains spermatogonial stem cells by inhibiting cell cycle regulators and RNA binding proteins, Nucleic Acids Res. 10.1093/nar/gkw1287
  2. Tu, Z., Bayazit, M. B., Liu, H., Zhang, J., Busayavalasa, K., Risal, S., Shao, J., Satyanarayana, A., Coppola, V., Tessarollo, L., Singh, M., Zheng, C., Han, C., Chen, Z., Kaldis, P., Gustafsson, J. A., and Liu, K. (2016) Speedy A-Cdk2 binding mediates initial telomere-nuclear envelope attachment during meiotic prophase I independent of Cdk2 activation, Proceedings of the National Academy of Sciences of the United States of America. 10.1073/pnas.1618465114
  3. Chen, M., Zhang, L., Cui, X., Lin, X., Li, Y., Wang, Y., Wang, Y., Qin, Y., Chen, D., Han, C., Zhou, B., Huff, V., and Gao, F. (2017) Wt1 directs the lineage specification of sertoli and granulosa cells by repressing Sf1 expression, Development 144, 44-53
  4. Wang, S., Wang, X., Ma, L., Lin, X., Zhang, D., Li, Z., Wu, Y., Zheng, C., Feng, X., Liao, S., Feng, Y., Chen, J., Hu, X., Wang, M., and Han, C. (2016) Retinoic Acid Is Sufficient for the In Vitro Induction of Mouse Spermatocytes, Stem cell reports 7, 80-94.
  5. Lin, X., Han, M., Cheng, L., Chen, J., Zhang, Z., Shen, T., Wang, M., Wen, B., Ni, T., and Han, C. (2016) Expression dynamics, relationships, and transcriptional regulations of diverse transcripts in mouse spermatogenic cells, RNA biology 13, 1011-1024.
  6. Wu, Y., Hu, X., Li, Z., Wang, M., Li, S., Wang, X., Lin, X., Liao, S., Zhang, Z., Feng, X., Wang, S., Cui, X., Wang, Y., Gao, F., Hess, R. A., and Han, C. (2016) Transcription Factor RFX2 Is a Key Regulator of Mouse Spermiogenesis, Scientific reports 6, 20435.
  7. Yang, Y., Feng, Y., Feng, X., Liao, S., Wang, X., Gan, H., Wang, L., Lin, X., and Han, C. (2016) BMP4 Cooperates with Retinoic Acid to Induce the Expression of Differentiation Markers in Cultured Mouse Spermatogonia, Stem cells international 2016, 9536192.
  8. Xue, Y., Lameijer, E. W., Ye, K., Zhang, K., Chang, S., Wang, X., Wu, J., Gao, G., Zhao, F., Li, J., Han, C., Xu, S., Xiao, J., Yang, X., Ying, X., Zhang, X., Chen, W. H., Liu, Y., Zhang, Z., Huang, K., and Yu, J. (2016) Precision Medicine: What Challenges Are We Facing?, Genomics, proteomics & bioinformatics 14, 253-261.
  9. Gao, Y., Bai, X., Zhang, D., Han, C., Yuan, J., Liu, W., Cao, X., Chen, Z., Shangguan, F., Zhu, Z., Gao, F., and Qin, Y. (2016) Mammalian elongation factor 4 regulates mitochondrial translation essential for spermatogenesis, Nature structural & molecular biology 23, 441-449.
  10. #Zhu, L., #Han, C. S., Cao, Z. L., Wang, Z. B., Han, R. G., Wang, B., and Sun, Q. Y. (2015) Confocal Microscopic Analysis of the Spindle and Chromosome Configurations of in vitro-Matured Oocytes from Different Types of Polycystic Ovary Syndrome Patients, Gynecologic and obstetric investigation 80, 179-186.
  11. Wang S.,Wang Xx.,Wu Yj., and *Han, C. (2015) ,IGF-1R Signaling Is Essential for the Proliferation of Cultured Mouse Spermatogonial Stem Cells by Promoting the G2/M Progression of the Cell Cycle,Stem Cells and Development 24,471-483。
  12. Li, Y., Wang, X., Feng, X., Liao, S., Zhang, D., Cui, X., Gao, F., and *Han, C. (2014) Generation of male germ cells from mouse induced pluripotent stem cells in vitro, Stem Cell Res 12, 517-530.
  13. *Han, C. (2014) ,Which one is the real matchmaker for the pair?,Asian Journal of Andrology 16,667-668。
  14. Gan, H., Wen, L., Liao, S., Lin, X., Ma, T., Liu, J., Song, C.-x., Wang, M., He, C., *Han, C., and *Tang, F. (2013) Dynamics of 5-hydroxymethylcytosine during mouse spermatogenesis,Nature Communications 4, 1995.
  15. Wang, F., Yang, Y., Lin, X., Wang, J. Q., Wu, Y. S., Xie, W., Wang, D., Zhu, S., Liao, Y. Q., Sun, Q., Yang, Y. G., *Guo, C., *Han, C., and *Tang, T. S. (2013) Genome-wide Loss of 5-hmC is a Novel Epigenetic Feature of Huntington's Disease, Human Molecular Genetics 22, 3641-3653.
  16. Wu, Y., Liao, S., Wang, X., Wang, S., Wang, M., and *Han, C. (2013) HSF2BP represses BNC1 transcriptional activity by sequestering BNC1 to the cytoplasm, FEBS Letters 587, 2099-2104.
  17. Shi, Y., Zhuang, X., Xu, B., Hua, J., Liao, S., Shi, Q., *Cooke, H. J., *Han, C. (2013) SYCP3-like X-linked 2 is expressed in meiotic germ cells and interacts with synaptonemal complex central element protein 2 and histone acetyltransferase TIP60, Gene 527, 352-359.
  18. Gan, H., Cai, T., Lin, X., Wu, Y., Wang, X., *Yang, F., and *Han, C. (2013) Integrative Proteomic and Transcriptomic Analyses Reveal Multiple Post-transcriptional Regulatory Mechanisms of Mouse Spermatogenesis, Mol Cell Proteomics 12, 1144-1157.
  19. Hou, X., Zhang, W., Xiao, Z., Gan, H., Lin, X., Liao, S., and *Han, C. (2012) Mining and characterization of ubiquitin E3 ligases expressed in the mouse testis, BMC Genomics 13, 495.
  20. Zhang, Y., Wang, S., Wang, X., Liao, S., Wu, Y., and *Han, C. (2012) Endogenously produced FGF2 is essential for the survival and proliferation of cultured mouse spermatogonial stem cells, Cell Research 22, 773-776.
  21. Gan, H., Lin, X., Zhang, Z., Zhang, W., Liao, S., Wang, L., and *Han, C. (2011) piRNA profiling during specific stages of mouse spermatogenesis, RNA 17, 1191-1203.