title: Temporal and spatial dissection of Shh signaling in genital tubercle development.
abstract: Genital tubercle (GT) initiation and outgrowth involve coordinated morphogenesis of surface ectoderm, cloacal mesoderm and hindgut endoderm. GT development appears to mirror that of the limb. Although Shh is essential for the development of both appendages, its role in GT development is much less clear than in the limb. Here, by removing Shh at different stages during GT development in mice, we demonstrate a continuous requirement for Shh in GT initiation and subsequent androgen-independent GT growth. Moreover, we investigated the Hh responsiveness of different tissue layers by removing or activating its signal transducer Smo with tissue-specific Cre lines, and established GT mesenchyme as the primary target tissue of Shh signaling. Lastly, we showed that Shh is required for the maintenance of the GT signaling center distal urethral epithelium (dUE). By restoring Wnt-Fgf8 signaling in Shh(-/-) cloacal endoderm genetically, we revealed that Shh relays its signal partly through the dUE, but regulates Hoxa13 and Hoxd13 expression independently of dUE signaling. Altogether, we propose that Shh plays a central role in GT development by simultaneously regulating patterning of the cloacal field and supporting an outgrowth signal.
authors.affiliation: Division of Dermatology, Washington University School of Medicine, 660 S. Euclid Avenue, St Louis, MO 63110, USA.
authors.forename: Congxing
authors.initials: C
authors.lastname: Lin
authors.forename: Yan
authors.initials: Y
authors.lastname: Yin
authors.forename: G Michael
authors.initials: GM
authors.lastname: Veith
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Fisher
authors.forename: Fanxin
authors.initials: F
authors.lastname: Long
authors.forename: Liang
authors.initials: L
authors.lastname: Ma
mesh_terms: D000818:Animals; D016923:Cell Death; D049109:Cell Proliferation; D004622:Embryo, Mammalian; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D018507:Gene Expression Regulation, Developmental; D005837:Genitalia, Male / Q000196:embryology* / Q000648:ultrastructure; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism*; D017403:In Situ Hybridization; D020287:In Situ Nick-End Labeling; D019426:Integrases; D008297:Male; D008648:Mesoderm / Q000166:cytology / Q000196:embryology; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D038081:Organogenesis; D011247:Pregnancy; D015398:Signal Transduction; D013997:Time Factors; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D053823:Hedgehog Proteins; C465570:Shh protein, mouse; C045073:Cre recombinase; D019426:Integrases; D001616:beta-Galactosidase