Heymann S, Koudrova M, Arnold H, Köster M, Braun T
Department of Cell and Molecular Biology, University of Braunschweig, Spielmannstr. 7, Braunschweig, 38106, Federal Republic of Germany.
Dev Biol. 1996 Dec 15;180(2):566-78. doi: 10.1006/dbio.1996.0329.
Limb muscles of vertebrates are derived from migratory dermomyotomal cells which emanate from a limited number of somites located adjacent to the developing limb buds. We have generated additional limb buds in chicken embryos by implantation of FGF-beads into the interlimb region in order to analyze whether these somites can be programmed to supply ectopic limbs with myogenic precursor cells. We show that migrating myogenic precursor cells are released from somites at the level of the newly formed limb, even when cell migration into the natural limb has been completed. The implantation of FGF beads in the lateral plate mesoderm rapidly induces SF/HGF expression. FGF beads implanted between HH stages 10 and 12 inhibit limb bud formation or shift the normal limb position. When an additional FGF bead was implanted at the original limb position at HH stage 15, SF/HGF expression was transiently induced to low levels without inducing a new limb. This demonstrates that the initial induction of SF/HGF by FGF does not require limb formation. Expression of SF/HGF during early limb bud stages was found in the entire developing bud and the adjacent lateral plate mesoderm with direct contacts to the lateral edge of the dermomyotome. Later, the SF/HGF expression domain retracts to a distal region below the apical ectodermal ridge. To investigate the role of SF/HGF in the migratory process, we implanted beads soaked in SF/HGF-alone or together with FGF into different locations of the developing chick embryo. In the experiments SF/HGF caused delamination of migratory cells from the dermomyotomal epithelium but no chemotactic attraction of migrating cells toward the SF/HGF source.
脊椎动物的肢体肌肉源自迁移性的皮肌节细胞，这些细胞来自与发育中的肢芽相邻的有限数量的体节。为了分析这些体节是否可以被编程为向异位肢体提供成肌前体细胞，我们通过将FGF珠植入鸡胚的肢体间区域来生成额外的肢芽。我们发现，即使细胞向天然肢体的迁移已经完成，迁移的成肌前体细胞仍会从新形成肢体水平的体节中释放出来。在侧板中胚层植入FGF珠会迅速诱导SF/HGF表达。在HH分期10至12期之间植入的FGF珠会抑制肢芽形成或改变正常肢体位置。当在HH分期15期在原肢体位置额外植入一个FGF珠时，SF/HGF表达会被短暂诱导至低水平，但不会诱导新的肢体形成。这表明FGF对SF/HGF的初始诱导并不需要肢体形成。在早期肢芽阶段，SF/HGF的表达在整个发育中的芽以及与皮肌节外侧边缘直接接触的相邻侧板中胚层中被发现。后来，SF/HGF表达域退缩到顶端外胚层嵴下方的远端区域。为了研究SF/HGF在迁移过程中的作用，我们将浸泡过SF/HGF单独或与FGF一起的珠子植入发育中的鸡胚的不同位置。在实验中，SF/HGF导致迁移细胞从皮肌节上皮分层，但不会使迁移细胞向SF/HGF来源产生趋化吸引。
