Thin filament length dysregulation contributes to muscle weakness in nemaline myopathy patients with nebulin deficiency
Thin filament length dysregulation contributes to muscle weakness in nemaline myopathy patients with nebulin deficiency
复制标题
DOI：
10.1093/hmg/ddp168
复制
发表时间：
2009-07-01
影响因子：
3.5
通讯作者：
Granzier, Henk
中科院分区：
文献类型：
--
作者：
Ottenheijm, Coen A. C.;Witt, Christian C.;Granzier, Henk
线状肌病（NM）是最常见的非营养不良性先天性肌病。临床上NM最重要的特征是肌无力；然而，人们对这一弱点背后的机制知之甚少。在这里，我们研究了具有明确星云蛋白突变 (NM-NEB) 的 NM 患者的肌肉表型，采用多学科方法来研究细丝长度调节和肌肉收缩性能。 SDS-PAGE 和蛋白质印迹显示 NM-NEB 患者骨骼肌中的 Nebulin 水平大大降低，其中 Nebulin N 末端的降低最为显着。肌肉力学研究表明，NM-NEB 肌肉的发力能力降低了 60%，并且 NM-NEB 肌纤维中的力-肌节长度关系左移。这表明与对照肌肉相比，NM-NEB 肌肉中的力减小机制可能包括更短且不均匀的细丝长度。免疫荧光共聚焦显微镜和电子显微镜研究表明，平均细丝长度从对照肌肉中的大约 1.3 μm 减少到 NM-NEB 肌肉中的大约 0.75 μm。因此，本研究首次表明，由于星云蛋白突变，NM 患者存在明显的基因型-功能表型相关性，并为细丝长度失调导致星云蛋白突变 NM 患者肌肉无力的观点提供了证据。此外，我们观察到 Nebulin 缺陷小鼠肌肉和人类 NM-NEB 肌肉的收缩和结构表型之间存在惊人的相似性，这表明 Nebulin 敲除模型非常适合阐明 NM 肌肉无力的功能基础和制定治疗策略。
Nemaline myopathy (NM) is the most common non-dystrophic congenital myopathy. Clinically the most important feature of NM is muscle weakness; however, the mechanisms underlying this weakness are poorly understood. Here, we studied the muscular phenotype of NM patients with a well-defined nebulin mutation (NM-NEB), using a multidisciplinary approach to study thin filament length regulation and muscle contractile performance. SDS-PAGE and western blotting revealed greatly reduced nebulin levels in skeletal muscle of NM-NEB patients, with the most prominent reduction at nebulin's N-terminal end. Muscle mechanical studies indicated similar to 60% reduced force generating capacity of NM-NEB muscle and a leftward-shift of the force-sarcomere length relation in NM-NEB muscle fibers. This indicates that the mechanism for the force reduction is likely to include shorter and non-uniform thin filament lengths in NM-NEB muscle compared with control muscle. Immunofluorescence confocal microscopy and electron microscopy studies indicated that average thin filament length is reduced from similar to 1.3 mu m in control muscle to similar to 0.75 mu m in NM-NEB muscle. Thus, the present study is the first to show a distinct genotype-functional phenotype correlation in patients with NM due to a nebulin mutation, and provides evidence for the notion that dysregulated thin filament length contributes to muscle weakness in NM patients with nebulin mutations. Furthermore, a striking similarity between the contractile and structural phenotypes of nebulin-deficient mouse muscle and human NM-NEB muscle was observed, indicating that the nebulin knockout model is well suited for elucidating the functional basis of muscle weakness in NM and for the development of treatment strategies.