Transmission distortion by loss of p21 or p27 cyclin-dependent kinase inhibitors following competitive spermatogonial transplantation

Abstract

Spermatogonial stem cells (SSCs) undergo self-renewal division to support spermatogenesis. Although several positive regulators of SSC self-renewal have been identified, little is known about the mechanisms that negatively regulate SSCs. Here we developed a novel transplantation assay for SSCs and demonstrate that p21 and p27 cyclin-dependent kinase inhibitors play critical roles in SSC self-renewal and differentiation. Overexpression of p21 or p27 abrogated proliferation of cultured SSCs in vitro, and their expression levels were downregulated by exogenous self-renewal signals. In contrast, no apparent defects were found in p21 or p27-deficient SSCs by spermatogonial transplantation. However, competitive spermatogonial transplantation with WT SSCs revealed that the loss of either gene causes distortion of germline transmission: p21-deficiency facilitated mutant offspring production, whereas germline transmission was limited by p27-deficiency. Serial transplantation also showed that the loss of p27, but not p21, decreases secondary colony formation, suggesting that appropriate amounts of p27 are necessary for sustaining SSC selfrenewal. Thus, p21 and p27 cyclin-dependent kinase inhibitors play critical roles in germline transmission by regulating the balance between SSC self-renewal and differentiation, and competitive spermatogonial transplantation technique will be useful for analyzing subtle defects in spermatogenesis that are not evident by traditional spermatogonial transplantation.germline transmission | spermatogenesis | stem cell | cyclin-dependent kinase inhibitor | self-renewal

Peroxisome Proliferator-activated Receptor-D (PPARD) Coordinates Mouse Spermatogenesis by Modulating Extracellular Signal-regulated Kinase (ERK)-dependent Signaling

“…Previous studies show that p27 Ϫ/Ϫ mice have increased Sertoli cell number and daily sperm production, resulting in larger testes compared with wild-type mice (41,43). Similar results were observed in Ppard Ϫ/Ϫ mice in the present study compared with p27 Ϫ/Ϫ mice because lower expression of p27 was associated with increased Sertoli cell number, enhanced sperm production, and larger testes.…”

Cold-inducible RNA-binding protein (Cirp) interacts with Dyrk1b/Mirk and promotes proliferation of immature male germ cells in mice

“…Mice deficient in S-phase kinase-associated protein 2 (Skp2), which mediates ubiquitin-dependent degradation of p27, exhibit a progressive loss in spermatogenic cells (36). Conversely, testes from p27-knockout mice are significantly larger (37) and contain increased numbers of type A spermatogonia (38), and EpCAM + spermatogonia from the knockout mice proliferate more actively than those from wild-type mice do (39). We found that Cirp decreases the protein level of p27 and increases cell proliferation via Dyrk1b in MEFs and the spermatogonial cell line and that the p27 protein level and cells in G0 phase were increased in Cirp-deficient undifferentiated spermatogonia.…”

Targeting theGdnfGene in peritubular myoid cells disrupts undifferentiated spermatogonial cell development

“…FGF2 is expressed by Sertoli cells and was reported to enhance the ability of GDNF to maintain SSC proliferation in vitro (26,32,36,37). However, no significant differences were detected by ELISA in FGF2 protein levels in testes of 8-wk-old WT, Het, and cKO mice (Fig.…”