Robert B, Lyons G, Krabbenhoft K, Simandl B K, Houzelstein D, Fallon J, Buckingham M
Institut Pasteur, Paris, France.
Ann Genet. 1993;36(1):39-46.
In tetrapod vertebrates, limbs are formed as a result of inductive interactions between ectoderm and mesoderm. The mesoderm from the limb field induces the formation, in the ectoderm, of a pseudo-stratified epithelium, the apical ectodermal ridge, which in turn is required for limb mesoderm outgrowth and patterning. Homeobox genes from the msh family are expressed in the apical region of limb bud mesoderm. Using the potential of chick experimental embryology, we have demonstrated that these genes respond to ecto-mesodermal induction at this site and may be implicated in the response of the mesoderm to the ectodermal inductive activity. This property appears to be more general for the sites in the embryo which grow and are patterned as a result of interactions between ectoderm and subjacent mesoderm, since many of them are places for the expression of the msh-related genes (e.g. fronto-nasal and maxillary processes, tooth germ, genital tubercle). These genes might be implicated in patterning events at these sites through the activation of other genes directly involved in the definition of positional information, such as Hox genes.
在四足脊椎动物中，四肢的形成是外胚层和中胚层之间诱导相互作用的结果。肢体区域的中胚层诱导外胚层中形成假复层上皮，即顶端外胚层嵴，而这反过来又是肢体中胚层生长和模式形成所必需的。来自msh家族的同源框基因在肢芽中胚层的顶端区域表达。利用鸡实验胚胎学的潜力，我们已经证明这些基因在该部位对外中胚层诱导有反应，并且可能与中胚层对外胚层诱导活性的反应有关。对于胚胎中由于外胚层与下方中胚层之间的相互作用而生长并形成模式的部位来说，这种特性似乎更为普遍，因为其中许多部位都是与msh相关基因表达的场所（例如额鼻突和上颌突、牙胚、生殖结节）。这些基因可能通过激活其他直接参与位置信息定义的基因（如Hox基因）而参与这些部位的模式形成事件。
