Charcot-Marie-Tooth disease type 1A (CMT1A) is the most common inherited peripheral neuropathy caused by a 1.5 megabase tandem duplication of chromosome 17 harboring the PMP22 gene. This dose-dependent overexpression of PMP22 results in disrupted Schwann cell myelination of peripheral nerves. To get better insights into the underlying pathogenic mechanisms in CMT1A, we investigated the role of PMP22 duplication on cellular homeostasis in CMT1A mouse models and in patient-derived induced pluripotent stem cells differentiated into Schwann cell precursors (iPSC-SCPs). We performed lipidomic profiling and bulk RNA sequencing on sciatic nerves of two developing CMT1A mouse models and on CMT1A patient derived iPSC-SCPs. For the sciatic nerves of the CMT1A mice, cholesterol and lipid metabolism was dose-dependently downregulated throughout development. For the CMT1A iPSC-SCPs, transcriptional analysis unveiled a strong suppression of genes related to autophagy and lipid metabolism. Gene ontology enrichment analysis identified disturbances in pathways related to plasma membrane components and cell receptor signaling. Lipidomic analysis confirmed the severe dysregulation in plasma membrane lipids, particularly sphingolipids, in CMT1A iPSC-SCPs. Furthermore, we identified reduced lipid raft dynamics, disturbed plasma membrane fluidity, and impaired cholesterol incorporation and storage, all of which could result from altered lipid storage homeostasis in the patient-derived CMT1A iPSC-SCPs. Importantly, this phenotype could be rescued by stimulating autophagy and lipolysis. We conclude that PMP22 duplication disturbs intracellular lipid storage and leads to a more disordered plasma membrane due to an alteration in the lipid composition, which ultimately may lead to impaired axo-glial interactions. Moreover, targeting lipid handling and metabolism could hold promise for the treatment of CMT1A patients.

中文翻译：

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PMP22 复制失调人类雪旺细胞发育中的脂质稳态和质膜组织

腓骨肌萎缩症 1A 型 (CMT1A) 是最常见的遗传性周围神经病，由含有 PMP22 基因的 17 号染色体 1.5 兆碱基串联重复引起。 PMP22 的这种剂量依赖性过度表达会导致周围神经雪旺细胞髓鞘形成破坏。为了更好地了解 CMT1A 的潜在致病机制，我们研究了 PMP22 重复对 CMT1A 小鼠模型和患者来源的诱导多能干细胞分化为施万细胞前体 (iPSC-SCP) 细胞稳态的作用。我们对两个正在发育的 CMT1A 小鼠模型的坐骨神经和 CMT1A 患者衍生的 iPSC-SCP 进行了脂质组学分析和批量 RNA 测序。对于 CMT1A 小鼠的坐骨神经，胆固醇和脂质代谢在整个发育过程中呈剂量依赖性下调。对于 CMT1A iPSC-SCP，转录分析揭示了与自噬和脂质代谢相关的基因的强烈抑制。基因本体富集分析确定了与质膜成分和细胞受体信号传导相关的通路的干扰。脂质组学分析证实了 CMT1A iPSC-SCP 中质膜脂质（尤其是鞘脂）的严重失调。此外，我们还发现脂筏动力学降低、质膜流动性紊乱以及胆固醇掺入和储存受损，所有这些都可能是由于患者来源的 CMT1A iPSC-SCP 中脂质储存稳态的改变所致。重要的是，这种表型可以通过刺激自噬和脂肪分解来挽救。我们得出的结论是，PMP22 复制扰乱了细胞内脂质储存，并由于脂质成分的改变而导致质膜更加紊乱，最终可能导致轴突-神经胶质相互作用受损。此外，针对脂质处理和代谢可能为 CMT1A 患者的治疗带来希望。