title: FGF2 mediates mouse spermatogonial stem cell self-renewal via upregulation of Etv5 and Bcl6b through MAP2K1 activation.
abstract: Fibroblast growth factor 2 (FGF2) and glial cell line-derived neurotrophic factor (GDNF) are required to recapitulate spermatogonial stem cell (SSC) self-renewal in vitro. Although studies have revealed the role of the GDNF signaling pathway in SSCs, little is known about how FGF2 is involved. In the present study, we assessed the role of the FGF2 signaling pathway using a mouse germline stem (GS) cell culture system that allows in vitro expansion of SSCs. Adding GDNF or FGF2 induced phosphorylation of MAPK1/3, and adding the MAP2K1 inhibitor PD0325091 reduced GS cell proliferation and MAPK1/3 phosphorylation. Moreover, GS cells transfected with an activated form of Map2k1 not only upregulated Etv5 and Bcl6b gene expression, but also proliferated in an FGF2-independent manner, suggesting that they act downstream of MAP2K1 signaling to drive SSC self-renewal. Although GS cells transfected with Map2k1, Etv5 or Bcl6b showed normal spermatogonial markers, transplanting GS cells expressing Bcl6b into infertile mouse testes resulted in the formation of a germ cell tumor, suggesting that excessive self-renewal signals causes tumorigenic conversion. These results show that FGF2 depends on MAP2K1 signaling to drive SSC self-renewal via upregulation of the Etv5 and Bcl6b genes.
authors.affiliation: Department of Molecular Genetics, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Ishii
authors.forename: Mito
authors.initials: M
authors.lastname: Kanatsu-Shinohara
authors.forename: Shinya
authors.initials: S
authors.lastname: Toyokuni
authors.forename: Takashi
authors.initials: T
authors.lastname: Shinohara
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000494:pharmacology; D048369:MAP Kinase Kinase 1 / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D013093:Spermatogonia / Q000166:cytology*; D013234:Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C113027:Bcl6b protein, mouse; D004268:DNA-Binding Proteins; C513242:Etv5 protein, mouse; D051100:Glial Cell Line-Derived Neurotrophic Factor; D012097:Repressor Proteins; D014157:Transcription Factors; D016222:Fibroblast Growth Factor 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048369:MAP Kinase Kinase 1; C482127:Map2k1 protein, mouse