Charcot–Marie–Tooth disease Type 2E/1F (CMT2E/1F) is a peripheral neuropathy caused by mutations in neurofilament protein L (NFL), which is one of five neurofilament subunit proteins that co‐assemble to form neurofilaments in vivo. Prior studies on cultured cells have shown that CMT2E/1F mutations disrupt neurofilament assembly and lead to protein aggregation, suggesting a possible disease mechanism. However, electron microscopy of axons in peripheral nerve biopsies from patients has revealed accumulations of neurofilament polymers of normal appearance and no evidence of protein aggregates. To reconcile these observations, we reexamined the assembly of seven CMT2E/1F NFL mutants in cultured cells. None of the mutants assembled into homopolymers in SW13vim‐ cells, but P8R, P22S, L268/269P, and P440/441L mutant NFL assembled into heteropolymers in the presence of neurofilament protein M (NFM) alone, and N98S, Q332/333P, and E396/397K mutant NFL assembled in the presence of NFM and peripherin. P8R, P22S, N98S, L268/269P, E396/397K, and P440/441L mutant NFL co‐assembled into neurofilaments with endogenous NFL, NFM, and α‐internexin in cultured neurons, although the N98S and E396/397K mutants showed reduced filament incorporation, and the Q332/333P mutant showed limited incorporation. We conclude that all the mutants are capable of assembling into neurofilaments, but for some of the mutants this was dependent on the identity of the other neurofilament proteins available for co‐assembly, and most likely also their relative expression level. Thus, caution should be exercised when drawing conclusions about the assembly capacity of CMT2E/1F mutants based on transient transfections in cultured cells.

中文翻译：

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Charcot-Marie-Tooth病2E / 1F型突变型神经丝蛋白组装成神经丝。

Charcot–Marie–Tooth疾病2E / 1F型（CMT2E / 1F）是由神经丝蛋白L（NFL）突变引起的周围神经病变，NFL是在体内共同组装形成神经丝的五种神经丝亚基蛋白之一。对培养细胞的先前研究表明，CMT2E / 1F突变破坏神经丝组装并导致蛋白质聚集，提示可能的疾病机制。然而，患者外周神经活检中轴突的电子显微镜检查显示，正常外观的神经丝聚合物堆积，没有蛋白质聚集的迹象。为了使这些观察结果一致，我们重新检查了培养细胞中七个CMT2E / 1F NFL突变体的装配。没有一个突变体在SW13vim细胞中组装成均聚物，但是P8R，P22S，L268 / 269P，在单独存在神经丝蛋白M（NFM）的情况下，将P440 / 441L突变体NFL组装成杂聚物，在NFM和外围蛋白存在的情况下将N98S，Q332 / 333P和E396 / 397K突变体NFL组装成杂聚物。尽管N98S和E396 / 397K突变体显示出细丝减少，但P8R，P22S，N98S，L268 / 269P，E396 / 397K和P440 / 441L突变体NFL与培养的神经元中的内源性NFL，NFM和α-internexin共组装成神经丝。 Q332 / 333P突变体显示有限的掺入。我们得出的结论是，所有突变体都能够组装成神经丝，但对于某些突变体，这取决于可用于共装配的其他神经丝蛋白的身份，最可能还取决于它们的相对表达水平。从而，