Knockdown of fast skeletal myosin-binding protein C in zebrafish results in a severe skeletal myopathy
Knockdown of fast skeletal myosin-binding protein C in zebrafish results in a severe skeletal myopathy
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DOI：
10.1085/jgp.201511452
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发表时间：
2016-04-01
影响因子：
3.8
通讯作者：
Arner, Anders
中科院分区：
文献类型：
--
作者：
Li, Mei;Andersson-Lendahl, Monika;Arner, Anders
肌球蛋白结合蛋白C（MyBPC）在肌肉肌节与几个收缩和结构蛋白相互作用。人类心脏亚型（MyBPC-3）的突变或动物基因敲除与心肌病有关。活肌肉中快速骨骼同种型（MyBPC-2）的功能了解较少。这个问题是解决使用斑马鱼模型，结合基因表达数据与功能分析的收缩性和小角度X射线衍射测量细丝结构。使用吗啉代反义核苷酸将主要同种型的快速骨骼MyBPC-2B敲低>50%。这些吗啡肽表现出骨骼肌病变，细胞凋亡增加，与肌肉蛋白质降解相关的因子上调。Morphant肌肉有较短的肌节与更广泛的长度分布，较短的肌动蛋白丝，和更广泛的丝间距与对照组相比，这表明快速骨骼肌BPC有一个肌节组装的作用。由于肌肉尺寸的减小，主动力的减少超过预期，这表明MyBPC-2是在跨桥水平产生最佳力所必需的。MyBPC-2变形体的最大缩短速度显著增加，但当与肌节长度相关时，差异较小，反映了MyBPC-2B含量的降低和由此产生的肌病仅伴随着对肌丝缩短动力学的微小影响。在对照组中，来自小角度X射线散射的赤道图案显示，在主动收缩期间，相对较少的横桥被连接（如通过11和10赤道反射的强度比所评估的）。从放松和收缩的变形的X射线散射数据没有显着不同的控制。然而，与对照组相比，僵直状态下11：10强度比的增加较低，可能反映了MyBPC对跨桥相互作用的影响。总之，缺乏MyBPC-2导致严重的骨骼肌病变，伴有结构变化和肌肉无力。
Myosin-binding protein C (MyBPC) in the muscle sarcomere interacts with several contractile and structural proteins. Mutations in the cardiac isoform (MyBPC-3) in humans, or animal knockout, are associated with cardiomyopathy. Function of the fast skeletal isoform (MyBPC-2) in living muscles is less understood. This question was addressed using zebrafish models, combining gene expression data with functional analysis of contractility and small-angle x-ray diffraction measurements of filament structure. Fast skeletal MyBPC-2B, the major isoform, was knocked down by >50% using morpholino antisense nucleotides. These morphants exhibited a skeletal myopathy with elevated apoptosis and up-regulation of factors associated with muscle protein degradation. Morphant muscles had shorter sarcomeres with a broader length distribution, shorter actin filaments, and a wider interfilament spacing compared with controls, suggesting that fast skeletal MyBPC has a role in sarcomere assembly. Active force was reduced more than expected from the decrease in muscle size, suggesting that MyBPC-2 is required for optimal force generation at the cross-bridge level. The maximal shortening velocity was significantly increased in the MyBPC-2 morphants, but when related to the sarcomere length, the difference was smaller, reflecting that the decrease in MyBPC-2B content and the resulting myopathy were accompanied by only a minor influence on filament shortening kinetics. In the controls, equatorial patterns from small-angle x-ray scattering revealed that comparatively few cross-bridges are attached (as evaluated by the intensity ratio of the 11 and 10 equatorial reflections) during active contraction. X-ray scattering data from relaxed and contracting morphants were not significantly different from those in controls. However, the increase in the 11: 10 intensity ratio in rigor was lower compared with that in controls, possibly reflecting effects of MyBPC on the cross-bridge interactions. In conclusion, lack of MyBPC-2 results in a severe skeletal myopathy with structural changes and muscle weakness.