title: The loss of ventral ectoderm identity correlates with the inability to form an AER in the legless hindlimb bud.
abstract: We have characterized the early stages of murine hindlimb morphogenesis in the legless (lgl)mutant and non-mutant littermates. Initially the entire ventral ectoderm expresses many genetic markers characteristic of the AER (en-1, fgf-8, msx-2, dlx-2, cd44, and cx-43). Subsequently, the expression domain of most of these genes is restricted to the thickened ectoderm of the disto-ventral limb margin prior to forming an AER. In lgl, the expression of these genes is initiated but not maintained and the disto-ventral marginal ectoderm does not thicken. In contrast, Wnt7a expression is initiated and maintained in the dorsal ectoderm. The limb mesenchyme of lgl and non-mutant embryos initially expresses lmx-1b and fgf-10 uniformly. As the ventro-distal marginal ectoderm thickens, lmx-1b is progressively dorsally restricted in non-mutants but continues to be expressed ventrally in lgl hindlimb buds. These data suggest that establishment of a dorso-ventral ectodermal interface is not sufficient for AER formation and that restriction of lmx-1b to the dorsal mesenchyme is coordinately linked to AER formation.
authors.affiliation: Division of Developmental Biology Children's Hospital Research Foundation, 3333 Burnet Avenue, Cincinnati, OH 45229, USA. sheila.bell@chmcc.org
authors.forename: S M
authors.initials: SM
authors.lastname: Bell
authors.forename: C M
authors.initials: CM
authors.lastname: Schreiner
authors.forename: W J
authors.initials: WJ
authors.lastname: Scott
mesh_terms: D000015:Abnormalities, Multiple / Q000196:embryology / Q000235:genetics; D000818:Animals; D004475:Ectoderm / Q000502:physiology / Q000648:ultrastructure*; D005326:Fetal Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D051526:Fibroblast Growth Factor 10; D005346:Fibroblast Growth Factors / Q000096:biosynthesis / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D053823:Hedgehog Proteins; D006614:Hindlimb / Q000196:embryology*; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000235:genetics; D060850:LIM-Homeodomain Proteins; D008648:Mesoderm / Q000473:pathology; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D009024:Morphogenesis; D010641:Phenotype; D011506:Proteins / Q000502:physiology; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators / Q000502:physiology; D014157:Transcription Factors; D051153:Wnt Proteins
chemical_list: D005326:Fetal Proteins; C496464:Fgf10 protein, mouse; D051526:Fibroblast Growth Factor 10; D053823:Hedgehog Proteins; D018398:Homeodomain Proteins; C112149:LIM homeobox transcription factor 1 beta; D060850:LIM-Homeodomain Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; C465570:Shh protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D051153:Wnt Proteins; C490508:Wnt7a protein, mouse; D005346:Fibroblast Growth Factors