Ros M A, Macias D, Fallon J F, Hurle J M
Departamento de Anatomia y Biologia Celular, Universidad de Cantabria, Santander, Spain.
Anat Embryol (Berl). 1994 Oct;190(4):375-82. doi: 10.1007/BF00187295.
By in situ hybridization we studied the expression patterns of Msx and Hoxd genes during the late development of the chick leg autopodium (foot) and compared them to patterns during the experimental development of interdigital extra digits. Extra digits are induced in the third interdigital space after various experimental manipulations, such as transient isolation of the interdigit, or removal of the interdigital marginal ectoderm and mesoderm. Msx1 and Msx2 are normally expressed in the interdigital tissue programmed to die. Our experiment changes the fate of the interdigital tissue from cell death to chondrogenesis and provides a good model for studying Msx involvement in defining areas of programmed cell death. Among the proposed roles of Hoxd genes is their involvement in the specification of digit identity early in development. The induction of extra digits allows us to examine whether this new morphogenetic commitment of the interdigital tissues involves changes in the domains of expression of Hoxd genes. Our results show that extra digits develop without a previous modification of the normal pattern of expression of Msx or Hoxd genes. This observation does not support the correlation between the expression of Msx genes and programmed cell death and suggests a role for these genes in maintaining the interdigital tissue in an undifferentiated state. Our results show that an increased number of digits can be formed without modifications in the pattern of expression of the 5'-located Hoxd genes and suggest the existence of latent or residual digit organization mechanisms past the time when digits are normally determined, independent of Hoxd gene expression.
通过原位杂交技术，我们研究了Msx和Hoxd基因在鸡胚腿部 autopodium（足部）后期发育过程中的表达模式，并将其与实验诱导的指间额外趾发育过程中的模式进行了比较。在进行各种实验操作后，如暂时隔离指间组织，或去除指间边缘外胚层和中胚层，第三指间间隙会诱导出额外的趾。Msx1和Msx2通常在预定死亡的指间组织中表达。我们的实验将指间组织的命运从细胞死亡转变为软骨形成，为研究Msx参与确定程序性细胞死亡区域提供了一个良好的模型。在Hoxd基因所提出的作用中，包括它们在发育早期参与趾身份的确定。额外趾的诱导使我们能够研究指间组织这种新的形态发生承诺是否涉及Hoxd基因表达域的变化。我们的结果表明，额外趾的发育并没有预先改变Msx或Hoxd基因的正常表达模式。这一观察结果不支持Msx基因表达与程序性细胞死亡之间的相关性，并表明这些基因在使指间组织保持未分化状态方面发挥作用。我们的结果表明，在不改变5'端Hoxd基因表达模式的情况下，可以形成更多的趾，并表明在正常确定趾的时间之后，存在独立于Hoxd基因表达的潜在或残留趾组织机制。
