Schwann cell myelination occurred without basal lamina formation in laminin α2 chain-null mutant (dy3K/dy3K) mice
Schwann cell myelination occurred without basal lamina formation in laminin α2 chain-null mutant (dy3K/dy3K) mice
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作者：
Nakagawa, M;Miyagoe-Suzuki, Y;Takeda, S
层粘连蛋白α 2链是骨骼肌和外周神经系统中基底层的主要组分。层粘连蛋白α 2链缺陷导致缺裂蛋白的先天性肌营养不良，其不仅影响骨骼肌，而且影响外周和中枢神经系统。据报道，基底层的形成是周围神经系统髓鞘形成所必需的。事实上，层粘连蛋白α 2链表达大大减少的营养不良小鼠（dy/dy小鼠）的脊髓根显示出缺乏基底层和裸露轴突簇。为了研究层粘连蛋白α 2链和基底层在体内的作用，我们检查了dy（3 K）/dy（3 K）小鼠的外周神经系统，它们是层粘连蛋白α 2链的无效突变体。结果表明，髓鞘形成的存在，虽然雪旺细胞缺乏基底层在脊髓神经根的dy（3 K）/dy（3 K）小鼠，这表明基底层不是一个绝对的要求髓鞘形成在体内。免疫组化显示，脊髓神经根的神经内膜层粘连蛋白α 4链表达增加，层粘连蛋白α 5链保留。在dy（3 K）/dy（3 K）小鼠中，层粘连蛋白α 4和α 5链可能代替层粘连蛋白α 2链在髓鞘形成中起关键作用。此外，坐骨神经的运动传导速度与野生型同窝仔相比显著降低。这种传导速度的降低可能是由于在dy（3 K）/dy（3 K）小鼠中小的轴突直径、薄的髓鞘和Ranvier结的基底层的斑片状破坏。(C)2001 Wiley-Liss，Inc.
The laminin alpha2 chain is a major component of basal lamina in both skeletal muscle and the peripheral nervous system. Laminin alpha2 chain deficiency causes merosin-deficient congenital muscular dystrophy, which affects not only skeletal muscles, but also the peripheral and central nervous systems. It has been reported that the formation of basal lamina is required for myelination in the peripheral nervous system. In fact, the spinal root of dystrophic mice (dy/dy mice), whose laminin alpha2 chain expression is greatly reduced, shows lack of basal lamina and clusters of naked axons. To investigate the role of laminin alpha2 chain and basal lamina in vivo, we examined the peripheral nervous system of dy(3K)/dy(3K)mice, which are null mutants of laminin alpha2 chain. The results indicate the presence of myelination although Schwann cells lacked basal lamina in the spinal roots of dy(3K)/dy(3K) mice, suggesting that basal lamina is not an absolute requirement for myelination in vivo. Immunohistochemically, the expression of laminin alpha4 chain was increased and laminin alpha5 chain was preserved in the endoneurium of the spinal root. Laminin alpha4 and alpha5 chains may play the critical role in myelination instead of laminin alpha2 chain in dy(3K)/dy(3K)mice. In addition, the motor conduction velocity of the sciatic nerve was significantly reduced compared with that of wild-type littermate. This reduction in conduction velocity may be due to small axon diameter, thin myelin sheath and the patchy disruption of the basal lamina of the nodes of Ranvier in dy(3K)/dy(3K)mice. (C) 2001 Wiley-Liss, Inc.