Characterization of neuromuscular synapse function abnormalities in multiple Duchenne muscular dystrophy mouse models
Characterization of neuromuscular synapse function abnormalities in multiple Duchenne muscular dystrophy mouse models
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DOI：
10.1111/ejn.13249
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发表时间：
2016-06-01
影响因子：
3.4
通讯作者：
Plomp，Jaap J.
中科院分区：
文献类型：
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作者：
van der Pijl，Elizabeth M.;van Putten，Maaike;Plomp，Jaap J.
杜氏肌营养不良症（DMD）是一种由肌营养不良蛋白缺乏引起的X连锁肌病。肌营养不良蛋白存在于细胞内的肌膜处，将肌动蛋白连接到肌营养不良蛋白相关的糖蛋白复合物。有趣的是，它在神经肌肉接头（NMJ）的突触后富集，但其突触功能在很大程度上是未知的。肌营养不良蛋白同源物Utrophin也集中在NMJ，并在DMD中上调。DMD患者NMJ中肌营养不良蛋白的缺失可能导致神经肌肉传递缺陷，从而加重肌无力。我们研究了mdx小鼠（缺乏抗肌萎缩蛋白）和野生型小鼠的NMJ功能。此外，mdx/utrn+/−和mdx/utrn−/−小鼠（缺乏utrophin）用于研究utrophin水平的影响。三种Duchenne小鼠模型在体内比较时均表现出肌无力，mdx/utrn−/−小鼠最弱，离体肌收缩和电生理研究显示，所有模型的神经肌肉传递安全系数均降低。与野生型相比，NMJ的微型终板电位振幅小约40%，表明神经递质乙酰胆碱的突触后敏感性丧失。然而，神经刺激诱发的终板电位振幅无变化。因此，量子含量（即每个神经冲动释放的乙酰胆碱量子数）大大增加。在重症肌无力的NMJ中也发现了神经递质释放的这种稳态代偿性增加，其中自身抗体减少乙酰胆碱受体。然而，高频率神经刺激诱导过度终板电位下降。NMJ形态学研究表明，乙酰胆碱受体簇的碎片发生在所有模型中，mdx/utrn−/−小鼠中最严重。总的来说，我们在几种Duchenne小鼠模型中显示了轻度的“肌无力样”神经肌肉突触功能障碍，这可能会影响肌肉无力和变性。
Duchenne muscular dystrophy (DMD) is an X‐linked myopathy caused by dystrophin deficiency. Dystrophin is present intracellularly at the sarcolemma, connecting actin to the dystrophin‐associated glycoprotein complex. Interestingly, it is enriched postsynaptically at the neuromuscular junction (NMJ), but its synaptic function is largely unknown. Utrophin, a dystrophin homologue, is also concentrated at the NMJ, and upregulated in DMD. It is possible that the absence of dystrophin at NMJs in DMD causes neuromuscular transmission defects that aggravate muscle weakness. We studied NMJ function inmdxmice (lacking dystrophin) and wild type mice. In addition,mdx/utrn+/−andmdx/utrn−/−mice (lacking utrophin) were used to investigate influences of utrophin levels. The three Duchenne mouse models showed muscle weakness when comparatively testedin vivo, withmdx/utrn−/−mice being weakest.Ex vivomuscle contraction and electrophysiological studies showed a reduced safety factor of neuromuscular transmission in all models. NMJs had ~ 40% smaller miniature endplate potential amplitudes compared with wild type, indicating postsynaptic sensitivity loss for the neurotransmitter acetylcholine. However, nerve stimulation‐evoked endplate potential amplitudes were unchanged. Consequently, quantal content (i.e. the number of acetylcholine quanta released per nerve impulse) was considerably increased. Such a homeostatic compensatory increase in neurotransmitter release is also found at NMJs in myasthenia gravis, where autoantibodies reduce acetylcholine receptors. However, high‐rate nerve stimulation induced exaggerated endplate potential rundown. Study of NMJ morphology showed that fragmentation of acetylcholine receptor clusters occurred in all models, being most severe inmdx/utrn−/−mice. Overall, we showed mild ‘myasthenia‐like’ neuromuscular synaptic dysfunction in several Duchenne mouse models, which possibly affects muscle weakness and degeneration.