title: FGF signaling directs a center-to-pole expansion of tubulogenesis in mouse testis differentiation.
abstract: In mouse embryogenesis, Sry is transiently activated in a center-to-pole wavelike manner along the anteroposterior (AP) axis of developing XY gonads. However, the mechanism and significance of the center-to-pole expansion of testis initiation pathways downstream of Sry expression remain unclear. Here we demonstrate that FGF9 can act as a diffusible conductor for a poleward expansion of tubulogenic programs at early phases of testis differentiation. In XY genital ridge cultures of anterior, middle and posterior segments at 11.0-11.25 days post-coitum, male-specific activation of Sry and its target gene, Sox9, was still observed in both anterior and posterior pole segments despite their isolation from the central domain. However, high-level Sox9 expression was not maintained, resulting in the failure of testis cord organization in most pole segments. A reconstruction experiment using ROSA:lacZ middle segments showed rescue of the tubulogenic defect in the poles without any appreciable contribution of lacZ-positive gonadal parenchyma cells. A partition culture assay also showed a possible contribution of soluble/diffusible factors secreted from the gonadal center domain to proper tubulogenesis in the poles. Among various signaling factors, Fgf9 expression was significantly lower in both anterior and posterior pole segments than in the central domain. The supportive role of the central domain could be substituted by exogenous FGF9 supply, whereas reduction of Wnt4 activity did not rescue the tubulogenesis defect in the pole segments. These observations imply that center-to-pole FGF9 diffusion directs a poleward expansion of testiculogenic programs along the AP axis of developing XY gonads.
authors.affiliation: Department of Veterinary Anatomy, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-8657, Japan.
authors.forename: Ryuji
authors.initials: R
authors.lastname: Hiramatsu
authors.forename: Kyoko
authors.initials: K
authors.lastname: Harikae
authors.forename: Naoki
authors.initials: N
authors.lastname: Tsunekawa
authors.forename: Masamichi
authors.initials: M
authors.lastname: Kurohmaru
authors.forename: Isao
authors.initials: I
authors.lastname: Matsuo
authors.forename: Yoshiakira
authors.initials: Y
authors.lastname: Kanai
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D047108:Embryonic Development / Q000187:drug effects / Q000235:genetics; D005260:Female; D051525:Fibroblast Growth Factor 9 / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D051379:Mice; D009924:Organ Culture Techniques; D011247:Pregnancy; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055758:SOX9 Transcription Factor / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D013737:Testis / Q000166:cytology / Q000196:embryology*; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism; D060528:Wnt4 Protein
chemical_list: C496460:Fgf9 protein, mouse; D051525:Fibroblast Growth Factor 9; D055758:SOX9 Transcription Factor; D051153:Wnt Proteins; D060528:Wnt4 Protein; C555582:Wnt4 protein, mouse; D005346:Fibroblast Growth Factors