Studies on the Molecular Mechanisms of Cartilage Pattern Formation in Chick Limb Bud

为了阐明鸡肢芽软骨形态形成的分子机制，将已知的诱导肢体复制的维甲酸(RA)局部应用于肢芽的不同区域或在培养的肢体中胚层细胞中添加视黄酸(RA)。RA作用于肢芽前远端可诱导ZPA活性，并刺激RARbeta基因的表达。ZPA活性的诱导与重复形成无关，并依赖于肢芽远端顶端AER的存在。RA诱导肢芽细胞培养形成18kD蛋白。这种诱导只发生在前部和远侧部的细胞中。细胞培养中ZPA活性的诱导也仅在这些细胞中发生，提示18kD蛋白在ZPA诱导中的作用。RA促进培养的肢芽中胚层细胞的增殖和软骨形成。这些结果表明，RA在体内和体外诱导ZPA活性、促进细胞增殖和软骨形成有共同的机制。。

To elucidate the molecular mechanisms of cartilage pattern formation of chick limb bud, retinoic acid (RA), which was known to induce limb duplication, was locally applied to the various regions of the limb bud or added to the limb mesodermal cells in culture. RA applied to the antero-distal region of the limb bud induced ZPA activity and stimulated the expression of RARbeta mRNA. The induction of ZPA activity was independently of duplicate formation and depended on the presence of AER at the distal top of the limb bud.RA induced the formation of 18kD protein in limb bud cell culture. This induction occurred only in the cells of anterior and distal region. Induction of ZPA activity in cell culture also occurred only in these cells, suggesting the role of 18kD protein in ZPA induction.RA promotes the proliferation and chondrogenesis in cultured distal mesodermal cells of limb bud. This promotion also occurred in the cells of antero-distal region.These results suggest a common mechanism in the induction of ZPA activity in vivo and in vitro and the promotion of cell proliferation and chondrogenesis by RA. .