van der Meulen T, Schipper H, van Leeuwen J L, Kranenbarg S
Experimental Zoology Group, Wageningen Institute of Animal Sciences, Wageningen University, The Netherlands.
J Exp Biol. 2005 Oct;208(Pt 19):3675-87. doi: 10.1242/jeb.01826.
The present paper discusses the effects of decreased muscle activity (DMA) on embryonic development in the zebrafish. Wild-type zebrafish embryos become mobile around 18 h post-fertilisation, long before the axial musculature is fully differentiated. As a model for DMA, the nic(b107) mutant was used. In nic(b107) mutant embryos, muscle fibres are mechanically intact and able to contract, but neuronal signalling is defective and the fibres are not activated, rendering the embryos immobile. Despite the immobility, distinguished slow and fast muscle fibres developed at the correct location in the axial muscles, helical muscle fibre arrangements were detected and sarcomere architecture was generated. However, in nic(b107) mutant embryos the notochord is flatter and the cross-sectional body shape more rounded, also affecting muscle fibre orientation. The stacking of sarcomeres and myofibril arrangement show a less regular pattern. Finally, expression levels of several genes were changed. Together, these changes in expression indicate that muscle growth is not impeded and energy metabolism is not changed by the decrease in muscle activity but that the composition of muscle is altered. In addition, skin stiffness is affected. In conclusion, the lack of muscle fibre activity did not prevent the basal muscle components developing but influenced further organisation and differentiation of these components.
本文讨论了肌肉活动减少（DMA）对斑马鱼胚胎发育的影响。野生型斑马鱼胚胎在受精后约18小时开始活动，远早于轴向肌肉组织完全分化。作为DMA的模型，使用了nic(b107)突变体。在nic(b107)突变体胚胎中，肌纤维在机械上是完整的且能够收缩，但神经信号传导有缺陷，纤维未被激活，导致胚胎无法活动。尽管胚胎无法活动，但在轴向肌肉的正确位置仍发育出了明显的慢肌纤维和快肌纤维，检测到了螺旋状肌纤维排列并形成了肌节结构。然而，在nic(b107)突变体胚胎中，脊索更扁平，身体横截面形状更圆，这也影响了肌纤维的方向。肌节的堆叠和肌原纤维的排列显示出不太规则的模式。最后，几个基因的表达水平发生了变化。这些表达变化共同表明，肌肉生长并未因肌肉活动减少而受到阻碍，能量代谢也未改变，但肌肉的组成发生了改变。此外，皮肤硬度也受到影响。总之，肌纤维活动的缺乏并未阻止基础肌肉成分的发育，但影响了这些成分的进一步组织和分化。
