AIMS A 25-base pair deletion in the cardiac myosin binding protein-C (cMyBP-C) gene (MYBPC3), proposed to skip exon 33, modifies the C10 domain (cMyBP-CΔC10mut) and is associated with hypertrophic cardiomyopathy (HCM) and heart failure, affecting approximately 100 million South Asians. However, the molecular mechanisms underlying the pathogenicity of cMyBP-CΔC10mutin vivo are unknown. We hypothesized that expression of cMyBP-CΔC10mut exerts a poison polypeptide effect leading to improper assembly of cardiac sarcomeres and the development of HCM. METHODS AND RESULTS To determine whether expression of cMyBP-CΔC10mut is sufficient to cause HCM and contractile dysfunction in vivo, we generated transgenic (TG) mice having cardiac-specific protein expression of cMyBP-CΔC10mut at approximately half the level of endogenous cMyBP-C. At 12 weeks of age, significant hypertrophy was observed in TG mice expressing cMyBP-CΔC10mut (heart weight/body weight ratio: 4.43 ± 0.11 mg/g non-transgenic (NTG) vs. 5.34 ± 0.25 mg/g cMyBP-CΔC10mut, P < 0.05). Furthermore, haematoxylin and eosin, Masson's trichrome staining, as well as second-harmonic generation imaging revealed the presence of significant fibrosis and a greater relative nuclear area in cMyBP-CΔC10mut hearts compared with NTG controls. M-mode echocardiography analysis revealed hypercontractile hearts (EF: 53.4%±2.9% NTG vs. 66.4% ± 4.7% cMyBP-CΔC10mut; P < 0.05) and early diastolic dysfunction (E/E': 28.7 ± 3.7 NTG vs. 46.3 ± 8.4 cMyBP-CΔC10mut; P < 0.05), indicating the presence of an HCM phenotype. To assess whether these changes manifested at the myofilament level, contractile function of single skinned cardiomyocytes was measured. Preserved maximum force generation and increased Ca2+-sensitivity of force generation were observed in cardiomyocytes from cMyBP-CΔC10mut mice compared with NTG controls (EC50: 3.6 ± 0.02 µM NTG vs. 2.90 ± 0.01 µM cMyBP-CΔC10mut; P < 0.0001). CONCLUSION Expression of cMyBP-C protein with a modified C10 domain is sufficient to cause contractile dysfunction and HCM in vivo.

中文翻译：

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心肌肌球蛋白结合蛋白 C 中 C10 结构域的改变会导致肥厚性心肌病。


目的 心肌肌球蛋白结合蛋白 C (cMyBP-C) 基因 (MYBPC3) 中的 25 个碱基对缺失，建议跳过外显子 33，修饰 C10 结构域 (cMyBP-CΔC10mut)，并与肥厚型心肌病 (HCM) 和心力衰竭，影响约 1 亿南亚人。然而，cMyBP-CΔC10mutin 体内致病性的分子机制尚不清楚。我们假设 cMyBP-CΔC10mut 的表达发挥毒多肽效应，导致心脏肌节组装不当和 HCM 的发展。方法和结果 为了确定 cMyBP-CΔC10mut 的表达是否足以在体内引起 HCM 和收缩功能障碍，我们生成了转基因 (TG) 小鼠，其心脏特异性蛋白表达的 cMyBP-CΔC10mut 约为内源性 cMyBP-C 水平的一半。 12 周龄时，表达 cMyBP-CΔC10mut 的 TG 小鼠观察到明显肥大（心脏重量/体重比：4.43 ± 0.11 mg/g 非转基因 (NTG) 对比 5.34 ± 0.25 mg/g cMyBP-CΔC10mut，P < 0.05)。此外，苏木精和曙红、Masson 三色染色以及二次谐波生成成像显示，与 NTG 对照相比，cMyBP-CΔC10mut 心脏中存在显着的纤维化和更大的相对核面积。 M 型超声心动图分析显示心脏收缩过度（EF：53.4%±2.9% NTG 对比 66.4% ± 4.7% cMyBP-CΔC10mut；P < 0.05）和早期舒张功能障碍（E/E'：28.7 ± 3.7 NTG 对比 46.3） ± 8.4 cMyBP-CΔC10mut；P < 0.05)，表明存在 HCM 表型。为了评估这些变化是否表现在肌丝水平，测量了单皮心肌细胞的收缩功能。 与 NTG 对照相比，在 cMyBP-CΔC10mut 小鼠的心肌细胞中观察到保留的最大力生成和力生成的 Ca2+ 敏感性增加（EC50：3.6 ± 0.02 µM NTG 对比 2.90 ± 0.01 µM cMyBP-CΔC10mut；P < 0.0001）。结论 具有修饰的 C10 结构域的 cMyBP-C 蛋白的表达足以引起体内收缩功能障碍和 HCM。