Ros M A, Piedra M E, Fallon J F, Hurle J M
Department of Anatomy and Cellular Biology, University of Cantabria, Santander, Spain.
Dev Dyn. 1997 Mar;208(3):406-19. doi: 10.1002/(SICI)1097-0177(199703)208:3<406::AID-AJA11>3.0.CO;2-Y.
There is evidence that the interdigital mesoderm may be in an undifferentiated state. For example, under experimental manipulation in vivo it may be diverted from cell death to digit formation. In the present work we wanted to analyze the maximum morphogenetic potential of the interdigital cells. To do this we made recombinant limbs of three types, the first using dissociated-reaggregated leg interdigital mesoderm, the second using the same tissue but without dissociation and the third adding a piece of polarizing region to the dissociated interdigit. In all three the massive cell death of the interdigit failed to occur. The first type of recombinant formed a small nodule of cartilage while the other two formed a well-developed digit. Our data indicate that the maximum morphogenetic potential of the interdigital tissue appears constrained to form digits and that dissociation of the tissue decreased this ability; polarizing region restores the ability of dissociated cell recombinants to form a digit. We also analyzed in these recombinants the expression of a battery of genes implicated in interdigital cell death or in digital morphogenesis. The pattern of expression of each gene analyzed was identical in the three types of recombinant limbs. The expression of Msx1 and Msx2 genes was maintained under the ridge indicating a good interaction between the interdigital cells, both dissociated and undissociated, and the apical ridge. The expression of Hoxd-12, Hoxd-13 and Hoxa-13 genes was maintained in the recombinants, indicating that these cells carry information about their autopodial origin, and this correlates well with their distal restricted morphogenetic potential. Finally, the patterns of expression of the Bmp-2, Bmp-4 and Bmp-7 genes indicated that they are independently regulated in the recombinants and that Bmp-4 and Bmp-7 have wider expression domains than the areas of cell death that were only detected under the regressing apical ridge during day 3 of the experiment.
有证据表明，指间中胚层可能处于未分化状态。例如，在体内实验操作下，它可能从细胞死亡转向指的形成。在本研究中，我们想要分析指间细胞的最大形态发生潜能。为此，我们制作了三种类型的重组肢体，第一种使用解离后重新聚集的腿部指间中胚层，第二种使用相同的组织但不解离，第三种在解离的指间添加一块极化区域。在所有这三种情况下，指间的大量细胞死亡均未发生。第一种重组类型形成了一个小的软骨结节，而另外两种则形成了发育良好的指。我们的数据表明，指间组织的最大形态发生潜能似乎局限于形成指，并且组织的解离降低了这种能力；极化区域恢复了解离细胞重组体形成指的能力。我们还在这些重组体中分析了一系列与指间细胞死亡或指形态发生相关的基因的表达。在三种类型的重组肢体中，所分析的每个基因的表达模式都是相同的。Msx1和Msx2基因的表达在嵴下方维持，表明解离和未解离的指间细胞与顶端嵴之间存在良好的相互作用。Hoxd - 12、Hoxd - 13和Hoxa - 13基因的表达在重组体中维持，表明这些细胞携带有关其 autopodial 起源的信息，这与其远端受限的形态发生潜能密切相关。最后，Bmp - 2、Bmp - 4和Bmp - 7基因的表达模式表明它们在重组体中是独立调节的，并且Bmp - 4和Bmp - 7的表达域比仅在实验第3天退化的顶端嵴下方检测到的细胞死亡区域更宽。
