Abstract：
Dysferlin is a multi-functional protein that regulates membrane resealing, calcium homeostasis, and lipid metabolism in skeletal muscle. Genetic loss of dysferlin results in limb girdle muscular dystrophy 2B/2R (LGMD2B/2R) and other dysferlinopathies - rare untreatable muscle diseases that lead to permanent loss of ambulation in humans. The mild disease severity in dysferlin-deficient mice and diverse genotype-phenotype relationships in LGMD2B patients have prompted the development of new in vitro models for personalized studies of dysferlinopathy. Here the first 3-D tissue-engineered hiPSC-derived skeletal muscle (\"myobundle\") model of LGMD2B is described that exhibits compromised contractile function, calcium-handling, and membrane repair, and transcriptomic changes indicative of impaired oxidative metabolism and mitochondrial dysfunction. In response to the fatty acid (FA) challenge, LGMD2B myobundles display mitochondrial deficits and intracellular lipid droplet (LD) accumulation. Treatment with the ryanodine receptor (RyR) inhibitor dantrolene or the dissociative glucocorticoid vamorolone restores LGMD2B contractility, improves membrane repair, and reduces LD accumulation. Lastly, it is demonstrated that chemically induced chronic RyR leak in healthy myobundles phenocopies LGMD2B contractile and metabolic deficit, but not the loss of membrane repair capacity. Together, these results implicate intramyocellular Ca2+ leak as a critical driver of dysferlinopathic phenotype and validate the myobundle system as a platform to study LGMD2B pathogenesis.
摘要：
Dysferlin是一种多功能蛋白，可调节膜的重新密封，钙稳态，和骨骼肌中的脂质代谢。dyferlin的遗传损失导致四肢带型肌营养不良2B/2R（LGMD2B/2R）和其他异常疾病-罕见的无法治疗的肌肉疾病，导致人类永久性行走丧失。dhyperlin缺陷小鼠的轻度疾病严重程度和LGMD2B患者的不同基因型-表型关系促使了新的体外模型的开发，用于dhyperferlinopathy的个性化研究。这里描述了LGMD2B的第一个3-D组织工程hiPSC衍生的骨骼肌（\“myobundle\”）模型，该模型表现出受损的收缩功能，钙处理，和膜修复，和转录组变化表明受损的氧化代谢和线粒体功能障碍。为了应对脂肪酸（FA）挑战，LGMD2B肌束显示线粒体缺陷和细胞内脂滴（LD）积累。用ryanodine受体（RyR）抑制剂丹曲林或解离性糖皮质激素vamorolone治疗可恢复LGMD2B收缩力，改善膜修复，并减少LD积累。最后,已证明，化学诱导的慢性RyR泄漏在健康的肌束表型LGMD2B收缩和代谢缺陷，但不损失膜修复能力。一起,这些结果提示肌细胞内Ca2+渗漏是异常ferlinopathic表型的关键驱动因素,并验证了肌束系统作为研究LGMD2B发病机制的平台.
