Engrailed-1 misexpression in chick embryos prevents apical ridge formation but preserves segregation of dorsal and ventral ectodermal compartments |
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Authors: | Altabef M Logan C Tickle C Lumsden A |
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Affiliation: | Department of Developmental Neurobiology, King's College, Guy's Campus, London, SE1 9RT, United Kingdom. Muriel.Altabef@snv.jussieu.fr |
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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. |
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