title: Engrailed-1 misexpression in chick embryos prevents apical ridge formation but preserves segregation of dorsal and ventral ectodermal compartments.
abstract: Using lineage tracers, we recently showed dorsal and ventral ectodermal compartments along the sides of the body in chick embryos. The compartments are formed both in presumptive limb-forming regions where they position the apical ridge and also in presumptive interlimb (flank). Here we show, using a novel technique combining fate mapping and in situ hybridisation, that the ventral compartment coincides with the Engrailed-1 (En-1) domain of expression. This coincidence suggests that En-1 could maintain the ventral compartment and be necessary for apical ridge formation. To test this hypothesis, we ectopically expressed En-1 via retroviral transfer and then examined limb development and cell lineage restriction in the ectoderm. En-1 misexpression can completely prevent formation of both normal limbs and ectopic limbs induced in the flank by application of FGF-2. In both cases, there are no morphological signs of apical ectodermal ridge formation and expression of ridge-associated genes is undetectable. In striking contrast, the lineage restriction between dorsal and ventral ectoderm is not altered. Therefore, En-1 is involved in the regulation of ridge formation but not compartment maintenance.
authors.affiliation: Department of Developmental Neurobiology, King's College, Guy's Campus, London, SE1 9RT, United Kingdom. Muriel.Altabef@snv.jussieu.fr
authors.forename: M
authors.initials: M
authors.lastname: Altabef
authors.forename: C
authors.initials: C
authors.lastname: Logan
authors.forename: C
authors.initials: C
authors.lastname: Tickle
authors.forename: A
authors.initials: A
authors.lastname: Lumsden
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000235:genetics / Q000502:physiology*; D002642:Chick Embryo; D002828:Choristoma; D004475:Ectoderm / Q000502:physiology*; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental; D018014:Gene Transfer Techniques; D018398:Homeodomain Proteins / Q000235:genetics* / Q000502:physiology; D018878:Limb Buds / Q000187:drug effects / Q000502:physiology; D009024:Morphogenesis
chemical_list: D018398:Homeodomain Proteins; D016222:Fibroblast Growth Factor 2