Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.
Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.
Hum Mol Genet. 2019 Dec 15;28(24):4067-4077. doi: 10.1093/hmg/ddz249.
Dynamin 2 (DNM2) is a ubiquitously expressed GTPase implicated in many cellular functions such as membrane trafficking and cytoskeleton regulation. Dominant mutations in DNM2 result in tissue-specific diseases affecting peripheral nerves (Charcot-Marie-Tooth neuropathy, CMT) or skeletal muscles (centronuclear myopathy, CNM). However, the reason for this tissue specificity is unknown, and it remains unclear if these diseases share a common pathomechanism. To compare the disease pathophysiological mechanisms in skeletal muscle, we exogenously expressed wild-type DNM2 (WT-DNM2), the DNM2-CMT mutation K562E or DNM2-CNM mutations R465W and S619L causing adult and neonatal forms, respectively, by intramuscular adeno-associated virus (AAV) injections. All muscles expressing exogenous WT-DNM2 and CNM or CMT mutations exhibited reduced muscle force. However, only expression of CNM mutations and WT-DNM2 correlated with CNM-like histopathological hallmarks of nuclei centralization and reduced fiber size. The extent of alterations correlated with clinical severity in patients. Ultrastructural and immunofluorescence analyses highlighted defects of the triads, mitochondria and costameres as major causes of the CNM phenotype. Despite the reduction in force upon expression of the DNM2-CMT mutation, muscle histology and ultrastructure were almost normal. However, the neuromuscular junction was affected in all DNM2-injected muscles, with the DNM2-CMT mutation inducing the most severe alterations, potentially explaining the reduction in force observed with this mutant. In conclusion, expression of WT and CNM mutants recreate a CNM-like phenotype, suggesting CNM mutations are gain-of-function. Histological, ultrastructural and molecular analyses pointed to key pathways uncovering the different pathomechanisms involved in centronuclear myopathy or Charcot-Marie-Tooth neuropathy linked to DNM2 mutations.
动力蛋白 2（DNM2）是一种普遍表达的 GTPase，参与许多细胞功能，如膜运输和细胞骨架调节。DNM2 的显性突变导致组织特异性疾病，影响周围神经（遗传性运动感觉神经病，CMT）或骨骼肌（核性肌病，CNM）。然而，这种组织特异性的原因尚不清楚，也不清楚这些疾病是否具有共同的病理机制。为了比较骨骼肌疾病的病理生理机制，我们通过肌肉内腺相关病毒（AAV）注射，外源性表达野生型 DNM2（WT-DNM2）、导致成人和新生儿形式的 DNM2-CMT 突变 K562E 或 DNM2-CNM 突变 R465W 和 S619L。所有表达外源性 WT-DNM2 和 CNM 或 CMT 突变的肌肉均表现出肌肉力量降低。然而，只有 CNM 突变和 WT-DNM2 的表达与 CNM 样核中心化和纤维大小减小的组织病理学特征相关。改变的程度与患者的临床严重程度相关。超微结构和免疫荧光分析突出了三联体、线粒体和肌节的缺陷，这是 CNM 表型的主要原因。尽管表达 DNM2-CMT 突变会导致肌肉力量降低，但肌肉组织学和超微结构几乎正常。然而，所有 DNM2 注射肌肉的神经肌肉接头均受到影响，DNM2-CMT 突变诱导的改变最为严重，这可能解释了该突变引起的肌肉力量降低。总之，WT 和 CNM 突变体的表达再现了 CNM 样表型，提示 CNM 突变是功能获得性的。组织学、超微结构和分子分析指出了关键途径，揭示了与 DNM2 突变相关的核性肌病或遗传性运动感觉神经病的不同病理机制。
