Foxo1 is required in mouse spermatogonial stem cells for their maintenance and the initiation of spermatogenesis

Abstract

Spermatogonial stem cells (SSCs) capable of self-renewal and differentiation are the foundation for spermatogenesis. Although several factors important for these processes have been identified, the fundamental mechanisms regulating SSC self-renewal and differentiation remain unknown. Here, we investigated a role for the Foxo transcription factors in mouse spermatogenesis and found that Foxo1 specifically marks mouse gonocytes and a subset of spermatogonia with stem cell potential. Genetic analyses showed that Foxo1 was required for both SSC homeostasis and the initiation of spermatogenesis. Combined deficiency of Foxo1, Foxo3, and Foxo4 resulted in a severe impairment of SSC self-renewal and a complete block of differentiation, indicating that Foxo3 and Foxo4, although dispensable for male fertility, contribute to SSC function. By conditional inactivation of 3-phosphoinositide-dependent protein kinase 1 (Pdk1) and phosphatase and tensin homolog (Pten) in the male germ line, we found that PI3K signaling regulates Foxo1 stability and subcellular localization, revealing that the Foxos are pivotal effectors of PI3K-Akt signaling in SSCs. We also identified a network of Foxo gene targets -most notably Ret -that rationalized the maintenance of SSCs by the Foxos. These studies demonstrate that Foxo1 expression in the spermatogenic lineage is intimately associated with the stem cell state and revealed what we believe to be novel Foxo-dependent mechanisms underlying SSC selfrenewal and differentiation, with implications for common diseases, including male infertility and testicular cancer, due to abnormalities in SSC function.

Pelota mediates gonocyte maturation and maintenance of spermatogonial stem cells in mouse testes

“…Moreover, the absence of a new wave of spermatogenesis showed that self-renewal of SSCs is impaired in the absence of PELO. The dramatic disruption of spermatogenesis in Pelo-deficient mice is similar to that observed in mice lacking the Plzf, Etv5, Foxo1, or Shp2 genes, which regulate the self-renewal of SSCs (Costoya et al 2004, Simon et al 2007, Goertz et al 2011, Puri et al 2014.…”

“…6A, the levels of nuclear FOXO1 were significantly reduced in mutants compared with controls. We then investigated the expression levels of Lhx1, Ret, Sall4, and Dppa3 by qRT-PCR, whose expression levels were significantly attenuated in the testes of Foxo1-null mice (Goertz et al 2011). The expression levels of Sall4 and Dppa3 were significantly lower in mutant P7 and P14 testes compared with controls, whereas no significant differences were detected in the expression levels of Lhx1 and Ret between control and mutant testes (Fig.…”

“…Interestingly, gonocyte maturation to SSCs is demarcated by the translocation of FOXO1 from the cytoplasm to the nucleus (Goertz et al 2011). They showed that FOXO1 is localized in the cytoplasm of all gonocytes in testes at P1-P3 and undergoes a translocation from cytoplasm to nucleus at P3-P7.…”

“…Analyses of conditional FOXO1-knockout mice revealed that FOXO1 is not only critical for SSC self-renewal, but also for the transition of gonocytes to SSCs. During this transition, which occurs in the first week of postnatal development, the AKT-dependent phosphorylation of FOXO1 prevents its nuclear translocation, resulting in the inhibition of its transcriptional activity (Goertz et al 2011). Pelota (Pelo) is an evolutionarily conserved gene that has been identified in diverse species from archaebacteria to humans (Ragan et al 1996, Shamsadin et al 2000.…”

Yangjing Capsule extract promotes proliferation of GC-1 spg cells <i>via</i> up-regulated POU3F1 pathway

“…Self-renewal and differentiation of rodent SSCs including mouse (5), rat (6,7), and hamster (8), depend on the response to the growth factor glial cell line-derived neurotrophic factor (GDNF). By binding to the glycosylphosphatidylinositol-anchored cell surface molecule of GDNF family receptor alpha1 (GFRα1), GDNF is able to trigger the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway and up-regulate expression of POU3F1 and eventually lead to survival and proliferation of SSCs (9)(10)(11) (Figure 1). …”