Limb-girdle muscular dystrophy R7 is a rare genetic disease caused by homozygous or compound heterozygous variants in the titin-cap (TCAP) gene that results in the absence of the protein telethonin. The primary pathological features of limb-girdle muscular dystrophy R7 are fiber size variation, nuclear centralization, and abnormal mitochondrial distribution. The mechanisms underlying this disease are unclear, and there is currently no specific treatment for limb-girdle muscular dystrophy R7. This study established a Tcap-deficient mouse model to explore the disease mechanism of mitochondria dislocation and potential therapeutic strategies. We use methods such as proteomics, immunofluorescence, histopathological staining, and western blotting to explore the mechanism of mitochondrial dislocation. Moreover, in the quest for a prospective therapeutic intervention for this disorder, the adeno-associated virus serotype 2/9 was employed to deliver the Tcap gene into the muscles of these mice, facilitating preclinical experimentation. After 2 months and 7 months, the muscular phenotype was evaluated and selected mice were humanely euthanized for subsequent molecular and histological analysis. The phenotype of Tcap-/- mice mimicked that observed in individuals diagnosed with limb-girdle muscular dystrophy R7. This study elucidated the mechanism of mitochondrial dislocation in limb-girdle muscular dystrophy R7. Through our in vitro experiments, we discovered that telethonin aids in preserving the integrity of desmin by preventing truncation at the N-terminus. Additionally, telethonin combined with desmin and colocalized at the Z-disc. Research has shown that the Tcap gene plays a crucial role in controlling the desmin cytoskeleton organization. The absence of telethonin leads to a collapsed desmin cytoskeleton. This causes disorganization of the mitochondrial network, leading to mitochondrial dysfunction. In addition, the study investigated the efficacy of adeno-associated virus (AAV)-mediated Tcap replacement in Tcap-/- mice. By intramuscular delivery of AAV, we observed dramatic improvements in muscle phenotype, muscle pathology, CK levels, muscle magnetic resonance imaging, mitochondrial network organization, and mitochondrial function. The results of this study demonstrated that telethonin deficiency led to desmin cytoskeleton collapse that caused mitochondrial dislocation. AAV-mediated replacement therapy could be a promising safe and efficient treatment option for limb-girdle muscular dystrophy R7. The study highlights the potential of AAV-mediated replacement therapy for specific types of limb-girdle muscular dystrophy.

中文翻译：

---

基于 AAV 的 TCAP 递送挽救了肢带型肌营养不良症 R7 中的线粒体脱位


肢带型肌营养不良症 R7 是一种罕见的遗传病，由 titin-cap （TCAP） 基因的纯合或复合杂合变异引起，导致蛋白 telethonin 缺失。肢带型肌营养不良症 R7 的主要病理特征是纤维大小变化、核集中和线粒体分布异常。这种疾病的潜在机制尚不清楚，目前没有针对肢带肌营养不良症 R7 的特异性治疗方法。本研究建立了 Tcap 缺陷小鼠模型，以探讨线粒体脱位的疾病机制和潜在的治疗策略。我们使用蛋白质组学、免疫荧光、组织病理学染色和 western blotting 等方法来探索线粒体脱位的机制。此外，为了寻求针对这种疾病的前瞻性治疗干预，腺相关病毒血清型 2/9 被用于将 Tcap 基因递送到这些小鼠的肌肉中，从而促进临床前实验。2 个月和 7 个月后，评估肌肉表型，并对选定的小鼠实施人道安乐死，用于随后的分子和组织学分析。Tcap - / - 小鼠的表型模拟了在诊断为肢带肌营养不良症 R7 的个体中观察到的表型。本研究阐明了肢带肌营养不良症 R7 中线粒体脱位的机制。通过我们的体外实验，我们发现 telethonin 通过防止 N 端截断来帮助保持结蛋白的完整性。此外，telethonin 与 desmin 结合并在 Z 盘共定位。研究表明，Tcap 基因在控制结蛋白细胞骨架组织中起着至关重要的作用。 telethonin 的缺失导致结蛋白细胞骨架塌陷。这会导致线粒体网络紊乱，导致线粒体功能障碍。此外，该研究还调查了腺相关病毒 （AAV） 介导的 Tcap 替代治疗对 Tcap-/- 小鼠的疗效。通过肌内注射 AAV，我们观察到肌肉表型、肌肉病理、CK 水平、肌肉磁共振成像、线粒体网络组织和线粒体功能的显着改善。这项研究的结果表明，telethonin 缺乏导致结蛋白细胞骨架崩溃，从而导致线粒体脱位。AAV 介导的替代疗法可能是肢带型肌营养不良症 R7 的一种有前途的安全有效的治疗选择。该研究强调了 AAV 介导的替代疗法治疗特定类型的肢带型肌营养不良症的潜力。