Loss-of-function mutations in MECP2 cause Rett syndrome (RTT), a severe neurological disorder that mainly affects girls. Mutations in MECP2 do occur in males occasionally and typically cause severe encephalopathy and premature lethality. Recently, we identified a missense mutation (c.353G>A, p.Gly118Glu [G118E]), which has never been seen before in MECP2, in a young boy who suffered from progressive motor dysfunction and developmental delay. To determine whether this variant caused the clinical symptoms and study its functional consequences, we established two disease models, including human neurons from patient-derived iPSCs and a knock-in mouse line. G118E mutation partially reduces MeCP2 abundance and its DNA binding, and G118E mice manifest RTT-like symptoms seen in the patient, affirming the pathogenicity of this mutation. Using live-cell and single-molecule imaging, we found that G118E mutation alters MeCP2's chromatin interaction properties in live neurons independently of its effect on protein levels. Here we report the generation and characterization of RTT models of a male hypomorphic variant and reveal new insight into the mechanism by which this pathological mutation affects MeCP2's chromatin dynamics. Our ability to quantify protein dynamics in disease models lays the foundation for harnessing high-resolution single-molecule imaging as the next frontier for developing innovative therapies for RTT and other diseases.

中文翻译：

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MeCP2 的一种新的致病性突变会损害染色质关联，而与蛋白质水平无关

MECP2的功能丧失突变会导致雷特综合征 (RTT)，这是一种主要影响女孩的严重神经系统疾病。MECP2突变偶尔会在男性中发生，通常会导致严重的脑病和过早死亡。最近，我们在一名患有进行性运动功能障碍和发育迟缓的小男孩中发现了MECP2中以前从未见过的错义突变（c.353G>A，p.Gly118Glu [G118E]） 。为了确定这种变异是否引起临床症状并研究其功能后果，我们建立了两种疾病模型，包括来自患者来源的 iPSC 的人类神经元和敲入小鼠系。G118E 突变部分降低了 MeCP2 丰度及其 DNA 结合，并且 G118E 小鼠表现出患者中看到的类似 RTT 的症状，证实了该突变的致病性。使用活细胞和单分子成像，我们发现 G118E 突变改变了活神经元中 MeCP2 的染色质相互作用特性，而与其对蛋白质水平的影响无关。在这里，我们报告了雄性亚等位变体 RTT 模型的生成和表征，并揭示了这种病理突变影响 MeCP2 染色质动力学机制的新见解。我们量化疾病模型中蛋白质动态的能力为利用高分辨率单分子成像作为开发 RTT 和其他疾病创新疗法的下一个前沿奠定了基础。