TCF3 Regulates the Proliferation and Apoptosis of Human Spermatogonial Stem Cells by Targeting PODXL.

Dai Zhou,Wenbing Zhu,Xingming Wang,Xueheng Zhao,Zenghui Huang,Liu Xing,Ruiling Tang,Huan Zhang,Hongchuan Nie,Han Zhang,Hao Bo,Zhizhong Liu,Ke Tao,Liqing Fan,Jingyu Fan,Fang Zhu,Zuping He

doi:10.3389/fcell.2021.695545

Abstract

Spermatogonial stem cells (SSCs) are the initial cells for the spermatogenesis. Although much progress has been made on uncovering a number of modulators for the SSC fate decisions in rodents, the genes mediating human SSCs remain largely unclear. Here we report, for the first time, that TCF3, a member of the basic helix-loop-helix family of transcriptional modulator proteins, can stimulate proliferation and suppress the apoptosis of human SSCs through targeting podocalyxin-like protein (PODXL). TCF3 was expressed primarily in GFRA1-positive spermatogonia, and EGF (epidermal growth factor) elevated TCF3 expression level. Notably, TCF3 enhanced the growth and DNA synthesis of human SSCs, whereas it repressed the apoptosis of human SSCs. RNA sequencing and chromatin immunoprecipitation (ChIP) assays revealed that TCF3 protein regulated the transcription of several genes, including WNT2B, TGFB3, CCN4, MEGF6, and PODXL, while PODXL silencing compromised the stem cell activity of SSCs. Moreover, the level of TCF3 protein was remarkably lower in patients with spermatogenesis failure when compared to individuals with obstructive azoospermia with normal spermatogenesis. Collectively, these results implicate that TCF3 modulates human SSC proliferation and apoptosis through PODXL. This study is of great significance since it would provide a novel molecular mechanism underlying the fate determinations of human SSCs and it could offer new targets for gene therapy of male infertility.

Highlights

Spermatogonial stem cells (SSCs) reside along the basement membrane of the testicular seminiferous tubules, and they self-renew to maintain the stem cell pool of the testis and differentiate for the continuous production of spermatozoa (Kanatsushinohara et al, 2003; Yeh et al, 2011)
PCNA was found in 94.35% of TCF3-expressing cells (Figures 1E,F), which suggests that TCF3 may be involved in cell proliferation in human adult testes
These data implicate that TCF3 is primarily expressed in human SSCs with proliferation potential

Summary

Introduction

Spermatogonial stem cells (SSCs) reside along the basement membrane of the testicular seminiferous tubules, and they self-renew to maintain the stem cell pool of the testis and differentiate for the continuous production of spermatozoa (Kanatsushinohara et al, 2003; Yeh et al, 2011). In both rodents and primates, SSCs are restricted to A-type undifferentiated. SSCs are generally considered to be present in As spermatogonia (Lord and Oatley, 2017), many data indicate that Apr and Aal syncytium can re-enter As state by breaking the cytoplasmic bridge in an appropriate environment (Hara et al, 2014; Carrieri et al, 2017). The traditional models propose that Ad spermatogonia are the reserve stem cells, and they steadily generate Ap spermatogonia with adequate self-renewal potential to sustain the stem cell pool (Clermont, 1966), but there are still many controversies about the function of Ad and Ap (Hermann et al, 2009, 2010; Di Persio et al, 2017)

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Conclusion