title: Dose-dependent functions of fibroblast growth factor 9 regulate the fate of murine XY primordial germ cells.
abstract: Male differentiation of primordial germ cells (PGCs) is initiated by the inhibition of entry into meiosis and exposure to male-inducing factor(s), which are regulated by somatic elements of the developing gonad. Fibroblast growth factor 9 (FGF9) produced by pre-Sertoli cells is essential for male gonadal differentiation and also contributes to survival and male differentiation of XY PGCs. However, it is not clear how FGF9 regulates PGC fate. Using a PGC culture system, we identified dose-dependent, fate-determining functions of FGF9 in XY PGCs. Treatment with low levels of FGF9 (0.2 ng/ml) increased expression of male-specific Dnmt3L and Nanos2 in XY PGCs. Conversely, treatment with high levels of FGF9 (25 ng/ml) suppressed male-specific gene expression and stimulated proliferation of XY PGCs. Western blotting showed that low FGF9 treatment enhanced p38 MAPK (mitogen-activated protein kinase) phosphorylation in the same cells. In contrast, high FGF9 treatment significantly stimulated the ERK (extracellular signal-regulated kinase)1/2 signaling pathway in XY PGCs. We investigated the relationship between the ERK1/2 signaling pathway stimulated by high FGF9 and regulation of PGC proliferation. An ERK1/2 inhibitor (U0126) suppressed the PGC proliferation that would otherwise be stimulated by high FGF9 treatment, and increased Nanos2 expression in XY PGCs. Conversely, a p38 MAPK inhibitor (SB202190) significantly suppressed Nanos2 expression that would otherwise be stimulated by low FGF9 in XY PGCs. Taken together, our results suggest that stage-specific expression of FGF9 in XY gonads regulates the balance between proliferation and differentiation of XY PGCs in a dose-dependent manner.
authors.affiliation: Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, USA.
authors.forename: Ferhat
authors.initials: F
authors.lastname: Ulu
authors.affiliation: Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, USA.
authors.forename: Sung-Min
authors.initials: SM
authors.lastname: Kim
authors.affiliation: Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, USA.|Department of Animal Science, Kobe University, Kobe, Hyogo, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Yokoyama
authors.affiliation: Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, USA.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Yamazaki
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D051525:Fibroblast Growth Factor 9 / Q000502:physiology*; D005854:Germ Cells / Q000502:physiology*; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D061251:Primary Cell Culture
chemical_list: C496460:Fgf9 protein, mouse; D051525:Fibroblast Growth Factor 9
keywords: ERK1/2 signaling pathway; FGF9; XY primordial germ cells; cell proliferation; male differentiation; p38 signaling pathway