Yonei-Tamura S, Endo T, Yajima H, Ohuchi H, Ide H, Tamura K
Biological Institute, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan.
Dev Biol. 1999 Jul 1;211(1):133-43. doi: 10.1006/dbio.1999.9290.
During vertebrate limb development, the apical ectodermal ridge (AER) plays a vital role in both limb initiation and distal outgrowth of the limb bud. In the early chick embryo the prelimb bud mesoderm induces the AER in the overlying ectoderm. However, the direct inducer of the AER remains unknown. Here we report that FGF7 and FGF10, members of the fibroblast growth factor family, are the best candidates for the direct inducer of the AER. FGF7 induces an ectopic AER in the flank ectoderm of the chick embryo in a different manner from FGF1, -2, and -4 and activates the expression of Fgf8, an AER marker gene, in a cultured flank ectoderm without the mesoderm. Remarkably, FGF7 and FGF10 applied in the back induced an ectopic AER in the dorsal median ectoderm. Our results suggest that FGF7 and FGF10 directly induce the AER in the ectoderm both of the flank and of the dorsal midline and that these two regions have the competence for AER induction. Formation of the AER of the dorsal median ectoderm in the chick embryo is likely to appear as a vestige of the dorsal fin of the ancestors.
在脊椎动物肢体发育过程中，顶端外胚层嵴（AER）在肢体起始和肢芽远端生长中都起着至关重要的作用。在早期鸡胚中，前肢芽中胚层诱导覆盖其上的外胚层形成AER。然而，AER的直接诱导因子仍然未知。在此我们报告，成纤维细胞生长因子家族成员FGF7和FGF10是AER直接诱导因子的最佳候选者。FGF7以与FGF1、-2和-4不同的方式在鸡胚侧腹外胚层诱导异位AER，并在没有中胚层的培养侧腹外胚层中激活AER标记基因Fgf8的表达。值得注意的是，将FGF7和FGF10应用于背部可在背中线上皮诱导异位AER。我们的结果表明，FGF7和FGF10直接在侧腹和背中线的外胚层诱导AER，并且这两个区域具有诱导AER的能力。鸡胚背中线上皮AER的形成可能表现为祖先背鳍的遗迹。
