FGF-2 influences cell movements and gene expression during limb development.
FGF-2 is proposed to be an important ectodermal signal directing limb outgrowth and patterning. Consistent with this hypothesis we show that ectopic application of FGF-2 can maintain the apical ectodermal ridge (AER)-dependent expression of Sonic hedgehog (Shh), and AER-dependent zone of polarizing activity (ZPA) signaling. We also find that ectopic FGF-2 applied to the posterior wing bud caused a dramatic change in the morphology of the limb bud, and results in limbs that display a reduction in the length of individual skeletal elements and loss of digits. Associated with these morphological changes was an FGF-2-stimulated expansion and bifurcation of the expression domains of two posteriorly expressed genes, Shh and HoxD13. Applying FGF-2 at a central or anterior location in the limb bud did not alter the Shh expression domain or cause digit loss. To test whether ectopic application of FGF-2 into the posterior limb bud was influencing the movement of limb bud cells, we used the lipophilic dye DiI to map the behavior of posterior cells in response to FGF-2. In response to FGF-2 posterior limb bud cells move in both a proximal and a distal direction, causing the initially labeled cell population to bifurcate into two distinct domains. Our data suggest that FGF-2 is influencing limb outgrowth by modifying cell movements and subsequent position-specific cell-cell interactions that are important for limb morphogenesis.
Li
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Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana 70118, USA.
Anderson
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Reginelli
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Muneoka
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D000818:Animals; D002465:Cell Movement / Q000502:physiology*; D002642:Chick Embryo; D004527:Egg Proteins / Q000235:genetics; D005121:Extremities / Q000196:embryology*; D016222:Fibroblast Growth Factor 2 / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000235:genetics; D011956:Receptors, Cell Surface; D015398:Signal Transduction; D000072216:Zona Pellucida Glycoproteins
D004527:Egg Proteins; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D000072216:Zona Pellucida Glycoproteins; D016222:Fibroblast Growth Factor 2