title: Wnt5a is a cell-extrinsic factor that supports self-renewal of mouse spermatogonial stem cells.
abstract: The maintenance of spermatogonial stem cells (SSCs) provides the foundation for life-long spermatogenesis. Although glial-cell-line-derived neurotrophic factor and fibroblast growth factor 2 are crucial for self-renewal of SSCs, recent studies have suggested that other growth factors have important roles in controlling SSC fate. Because β-catenin-dependent Wnt signaling promotes self-renewal of various stem cell types, we hypothesized that this pathway contributes to SSC maintenance. Using transgenic reporter mice for β-catenin-dependent signaling, we found that this signaling was not active in SSCs in vitro and in most spermatogonia in vivo. Nonetheless, a pan-Wnt antagonist significantly reduced SSC activity in vitro, suggesting that some Wnt molecules exist in our serum-free culture system and contribute to SSC maintenance. Here, we report that Wnt5a promotes SSC activity. We found that Wnt5a-expressing fibroblasts supported SSC activity better than those not expressing Wnt5a in culture, and that recombinant Wnt5a stimulated SSC maintenance. Furthermore, Wnt5a promoted SSC survival in the absence of feeder cells, and this effect was abolished by inhibiting the Jun N-terminal kinase cascade. In addition, Wnt5a blocked β-catenin-dependent signaling. We detected the expression of Wnt5a and potential Wnt5a receptors in Sertoli cells and stem/progenitor spermatogonia, respectively. These results indicate that Wnt5a is a cell-extrinsic factor that supports SSC self-renewal through β-catenin-independent mechanisms.
authors.affiliation: Department of Obstetrics and Gynecology and Division of Experimental Medicine, McGill University, Montreal, QC H3A 1A1, Canada.
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Yeh
authors.forename: Xiangfan
authors.initials: X
authors.lastname: Zhang
authors.forename: Makoto C
authors.initials: MC
authors.lastname: Nagano
mesh_terms: D000818:Animals; D008297:Male; D051379:Mice; D015398:Signal Transduction; D013093:Spermatogonia / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D014162:Transfection; D051153:Wnt Proteins / Q000378:metabolism / Q000502:physiology*; D000071818:Wnt-5a Protein; D051176:beta Catenin / Q000378:metabolism
chemical_list: D051153:Wnt Proteins; D000071818:Wnt-5a Protein; C438615:Wnt5a protein, mouse; D051176:beta Catenin