Nemaline myopathy (NM) is a rare congenital neuromuscular disorder characterized by muscle weakness and hypotonia, slow gross motor development, and decreased respiratory function. Mutations in at least twelve genes, all of each encode proteins that are either components of the muscle thin filament or regulate its length and stability, have been associated with NM. Mutations in Nebulin (NEB), a giant filamentous protein localized in the sarcomere, account for more than 50% of NM cases. At present, there remains a lack of understanding of whether NEB genotype influences nebulin function and NM-patient phenotypes. In addition, there is a lack of therapeutically tractable models that can enable drug discovery and address the current unmet treatment needs of patients. To begin to address these gaps, here we have characterized five new zebrafish models of NEB-related NM. These mutants recapitulate most aspects of NEB-based NM, showing drastically reduced survival, defective muscle structure, reduced contraction force, shorter thin filaments, presence of electron-dense structures in myofibers, and thickening of the Z-disks. This study represents the first extensive investigation of an allelic series of nebulin mutants, and thus provides an initial examination in pre-clinical models of potential genotype-phenotype correlations in human NEB patients. It also represents the first utilization of a set of comprehensive outcome measures in zebrafish, including correlation between molecular analyses, structural and biophysical investigations, and phenotypic outcomes. Therefore, it provides a rich source of data for future studies exploring the NM pathomechanisms, and an ideal springboard for therapy identification and development for NEB-related NM.

中文翻译：

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NEB 相关线状肌病等位基因系列斑马鱼模型的综合表型特征

线形肌病 (NM) 是一种罕见的先天性神经肌肉疾病，其特征是肌肉无力和肌张力减退、粗大运动发育缓慢和呼吸功能下降。至少 12 个基因的突变（所有基因均编码蛋白质）与 NM 相关，这些蛋白质要么是肌肉细丝的组成部分，要么调节其长度和稳定性。Nebulin (NEB) 是一种位于肌节的巨大丝状蛋白，50% 以上的 NM 病例都是由其突变引起的。目前，对于 NEB 基因型是否影响 nebulin 功能和 NM 患者表型仍缺乏了解。此外，缺乏可实现药物发现并解决患者当前未满足的治疗需求的治疗上易于处理的模型。为了开始解决这些差距，我们在这里描述了五种新的 NEB 相关 NM 斑马鱼模型。这些突变体概括了基于 NEB 的 NM 的大部分方面，表现出存活率大幅降低、肌肉结构缺陷、收缩力降低、细丝变短、肌纤维中存在电子致密结构以及 Z 盘增厚。这项研究代表了对星云蛋白突变体等位基因系列的首次广泛研究，从而为人类 NEB 患者潜在基因型-表型相关性的临床前模型提供了初步检查。它还代表了首次在斑马鱼中使用一套综合结果测量，包括分子分析、结构和生物物理研究以及表型结果之间的相关性。因此，它为未来探索 NM 病理机制的研究提供了丰富的数据来源，并为 NEB 相关 NM 的治疗识别和开发提供了理想的跳板。