Rieger F, Bournaud R, Shimahara T, Garcia L, Pinçon-Raymond M, Romey G, Lazdunski M
Groupe de Biologie et Pathologie neuromusculaires, INSERM U.153, Paris, France.
Nature. 1987;330(6148):563-6. doi: 10.1038/330563a0.
Muscular dysgenesis (mdg) is a spontaneous recessive lethal mutation in the mouse. The disease is characterized by a total lack of excitation-contraction coupling in embryonic skeletal muscle. This developmental abnormality is associated with a drastic deficiency in the expression of voltage-sensitive Ca2+ channels in skeletal muscle without alteration of the properties of voltage-sensitive Na+ channels or of voltage-sensitive Ca2+ channels in cardiac and neuronal cells. Membrane couplings between sarcoplasmic reticulum and the transverse tubules, known as triads, were also found to be drastically altered in embryonic muscle of the homozygous mutant (mdg/mdg). Triads in the mdg/mdg muscle were less numerous, disorganized and lacked spaced densities. This paper shows that co-culture of mdg/mdg myotubes with normal spinal cord neurons re-establishes Ca2+ channel activity, contraction and normal triad organization. The decrease thus cannot be due to a mutation of the Ca2+ channel as previously suggested. Normal nerve cells may supply an essential factor to mutant muscle cells.
肌肉发育不全（mdg）是小鼠中的一种自发隐性致死突变。该疾病的特征是胚胎骨骼肌中完全缺乏兴奋-收缩偶联。这种发育异常与骨骼肌中电压敏感性Ca2+通道表达的严重缺陷有关，而心脏和神经元细胞中电压敏感性Na+通道或电压敏感性Ca2+通道的特性没有改变。在纯合突变体（mdg/mdg）的胚胎肌肉中，肌浆网与横管之间的膜偶联（称为三联体）也被发现发生了剧烈改变。mdg/mdg肌肉中的三联体数量较少、排列紊乱且缺乏间隔密度。本文表明，mdg/mdg肌管与正常脊髓神经元共培养可重新建立Ca2+通道活性、收缩和正常三联体组织。因此，这种减少不可能如先前所暗示的那样是由于Ca2+通道的突变。正常神经细胞可能为突变肌肉细胞提供一种必需因子。
