Mutations in MECP2 cause Rett syndrome (RTT), an X-linked neurological disorder characterized by regressive loss of neurodevelopmental milestones and acquired psychomotor deficits. However, the cellular heterogeneity of the brain impedes an understanding of how MECP2 mutations contribute to RTT. Here we developed a Cre-inducible method for cell-type-specific biotin tagging of MeCP2 in mice. Combining this approach with an allelic series of knock-in mice carrying frequent RTT-associated mutations (encoding T158M and R106W) enabled the selective profiling of RTT-associated nuclear transcriptomes in excitatory and inhibitory cortical neurons. We found that most gene-expression changes were largely specific to each RTT-associated mutation and cell type. Lowly expressed cell-type-enriched genes were preferentially disrupted by MeCP2 mutations, with upregulated and downregulated genes reflecting distinct functional categories. Subcellular RNA analysis in MeCP2-mutant neurons further revealed reductions in the nascent transcription of long genes and uncovered widespread post-transcriptional compensation at the cellular level. Finally, we overcame X-linked cellular mosaicism in female RTT models and identified distinct gene-expression changes between neighboring wild-type and mutant neurons, providing contextual insights into RTT etiology that support personalized therapeutic interventions.

中文翻译：

---

小鼠中MeCP2的生物素标记揭示了Rett综合征转录组的背景信息。

MECP2中的突变会引起Rett综合征（RTT），这是一种X连锁神经系统疾病，其特征是神经发育里程碑的逐渐消失和获得性精神运动缺陷。但是，大脑的细胞异质性妨碍了对MECP2突变如何促进RTT的理解。在这里，我们开发了一种Cre可诱导的方法，用于在小鼠中对MeCP2进行细胞类型特异性生物素标记。将该方法与携带频繁RTT相关突变（编码T158M和R106W）的等位基因敲除小鼠系列结合使用，可以在兴奋性和抑制性皮层神经元中对RTT相关核转录组进行选择性分析。我们发现，大多数基因表达变化主要是针对每种与RTT相关的突变和细胞类型。低表达的细胞类型富集基因优先被MeCP2突变破坏，其上调和下调的基因反映了不同的功能类别。MeCP2突变神经元中的亚细胞RNA分析进一步揭示了长基因新生转录的减少，并且在细胞水平上未发现广泛的转录后补偿。最后，我们克服了女性RTT模型中的X连锁细胞镶嵌现象，并确定了相邻野生型和突变型神经元之间的明显基因表达变化，从而提供了支持个性化治疗干预措施的RTT病因的背景知识。