Defining the spermatogonial stem cell

Abstract

Through the use of donor cells from transgenic rats expressing GFP exclusively in the germline, we have defined culture conditions where male germ cells lose (on STO cells) or maintain (on MSC-1 cells) stem cell activity. A cadre of germ cell transcripts strikingly decrease in relative abundance as a function of testis age or culture time on STO cells, but only a subset of these transcripts (approximately 248) remain elevated when cultured on MSC-1 cells. If specific gene expression regulates stem cell activity, some or all of these transcripts are candidates as such regulators. We establish a spermatogonial stem cell index (SSCI) that reliably predicts relative stem cell activity in rat or mouse testis cell cultures, and through the use of an antibody to a robust signal (Egr3) within the index find intense signals in single or paired cells. As germ cells form longer interconnected chains (incomplete cytokinesis), the Egr3 signal disappears coincident with a loss of stem cell activity. Thus, molecular markers specific for spermatogonial stem cells establish a reliable and rapid means by which to define these cells in culture and alleviate the need for laborious testicular transfers in initial cell culture studies.

Spermatogonial stem cell regulation and spermatogenesis

“…(2008)CD9FC, IHC, MACS, TryesXXXXXXKanatsu-Shinohara et al . (2004 b )EGR3IVC, IHCnot testedXXHamra et al . (2004)Ngn3ISH, TG, WM, IHC, Tryes (approx.…”

Transcriptional control of spermatogonial maintenance and differentiation

“…The first hint that Bcl6b might also have a role in SSCs was the discovery that it is highly expressed in rat germ cells enriched for SSC activity [30]. Its potential role in SSCs was reinforced when it was found that Bcl6b was among the suite of genes induced by GDNF in Thy1 + spermatogonial cell cultures [16].…”

“…Pou3f1 -mutant mice die shortly after birth with various defects in nervous system development, precluding an analysis of the role of POU3F1 in the testis [33,34]. Like Bcl6b , Pou3f1 was first recognized as a candidate to be involved in SSCs when it was shown to be highly expressed in rat germ cells enriched for SSC activity [30] and induced by the GDNF-PI3K-AKT pathway in mouse Thy1 + spermatogonial cell cultures [35]. Its functional role in SSCs was demonstrated by knockdown studies conducted by Wu et al .…”

“…FOXO1 was initially suspected of having a role in SSCs by virtue of its high expression in rat germ cells enriched for SSC activity [30]. To elucidate its functional role, Goertz et al .…”

Stem Cells as New Agents for the Treatment of Infertility: Current and Future Perspectives and Challenges

“…SSC can be found in the seminiferous tubule, lying near to the basement membrane [29]. Several markers could be used for the identification and isolation of SSC: spermatogonia-specific marker Stra8 for mouse SSC [30, 31], thymocyte antigen 1 (Thy-1), CD9, stage-specific embryonic antigen-4 (SSEA4), β 1 and α 6 integrins for rat SSC [32], SSEA4, and G-protein coupled receptor 125 (GPR125) for human SSC [33]. SSC are a potential tool for the treatment of male infertility due to their ability to differentiate into male gametes in vitro and capacity to restore male fertility in vivo [34, 35].…”