Early onset muscle weakness and disruption of muscle proteins in mouse models of spinal muscular atrophy
Early onset muscle weakness and disruption of muscle proteins in mouse models of spinal muscular atrophy
复制标题
DOI：
10.1186/2044-5040-3-24
复制
发表时间：
2013-01-01
期刊：
影响因子：
4.9
通讯作者：
Kothary, Rashmi
中科院分区：
文献类型：
--
作者：
Boyer, Justin G.;Murray, Lyndsay M.;Kothary, Rashmi
背景：儿童神经肌肉疾病脊髓性肌萎缩症（SMA）是由存活运动神经元（SMN1）基因突变或缺失引起的。虽然SMA传统上被认为是一种运动神经元疾病，但SMN的肌肉特异性需求从未得到充分定义。因此，本研究的目的是研究小鼠SMA模型的肌肉缺陷。方法：采用两种不同的小鼠SMA模型，重度Smn(-/-)；SMN2小鼠和较轻的Smn（2B/-）小鼠。我们用离体装置测量了对照肌和SMA模型小鼠通过直接刺激产生的最大力。通过免疫荧光和免疫印迹实验揭示小鼠SMA模型的肌肉缺陷。使用方差检验和学生t检验比较对照和SMA模型小鼠样本的均值。结果：我们报道了表型期为Smn（-/-）的胫骨前肌（TA）；与异常的运动神经元信号传递无关，SMN2小鼠产生的最大力量比对照小鼠少39%。此外，在肌肉疲劳时，Smn(-/-)；与对照组相比，SMN2肌肉出现早发，非刺激力增加。此外，我们证明了症状前Smn（-/-）显著减少肌肉的力量生产；SMN2和Smn（2B/-）小鼠，表明肌肉无力是在任何明显的运动神经元丧失和肌肉去神经支配之前发生的早期事件。肌肉萎缩症小鼠模型的肌肉无力与从新生儿到成年的重要的肌肉收缩的蛋白质亚型的过渡延迟有关，例如ryanodine受体和钠通道。后肢骨骼肌提取物的免疫印迹分析显示肌浆网Ca2+ atp酶水平异常。结论：这项研究的结果揭示了肌肉收缩重要的成熟蛋白亚型的出现延迟，以及疾病病因早期的肌肉无力，从而突出了骨骼肌缺陷对SMA表型的贡献。
Background: The childhood neuromuscular disease spinal muscular atrophy (SMA) is caused by mutations or deletions of the survival motor neuron (SMN1) gene. Although SMA has traditionally been considered a motor neuron disease, the muscle-specific requirement for SMN has never been fully defined. Therefore, the purpose of this study was to investigate muscle defects in mouse models of SMA.Methods: We have taken advantage of two different mouse models of SMA, the severe Smn(-/-); SMN2 mice and the less severe Smn(2B/-) mice. We have measured the maximal force produced from control muscles and those of SMA model mice by direct stimulation using an ex vivo apparatus. Immunofluorescence and immunoblot experiments were performed to uncover muscle defects in mouse models of SMA. Means from control and SMA model mice samples were compared using an analysis of variance test and Student's t tests.Results: We report that tibialis anterior (TA) muscles of phenotype stage Smn(-/-); SMN2 mice generate 39% less maximal force than muscles from control mice, independently of aberrant motor neuron signal transmission. In addition, during muscle fatigue, the Smn(-/-); SMN2 muscle shows early onset and increased unstimulated force compared with controls. Moreover, we demonstrate a significant decrease in force production in muscles from pre-symptomatic Smn(-/-); SMN2 and Smn(2B/-) mice, indicating that muscle weakness is an early event occurring prior to any overt motor neuron loss and muscle denervation. Muscle weakness in mouse models of SMA was associated with a delay in the transition from neonatal to adult isoforms of proteins important for proper muscle contractions, such as ryanodine receptors and sodium channels. Immunoblot analyses of extracts from hindlimb skeletal muscle revealed aberrant levels of the sarcoplasmic reticulum Ca2+ ATPase.Conclusions: The findings from this study reveal a delay in the appearance of mature isoforms of proteins important for muscle contractions, as well as muscle weakness early in the disease etiology, thus highlighting the contributions of skeletal muscle defects to the SMA phenotype.