Restoration of Homeostasis of Downstream Targets of MeCP2 as a Potential Therapeutic Avenue for Rett Syndrome

项目总结/摘要 Rett综合征（RTT）是一种严重的X连锁进展性疾病，目前尚无有效的治疗方法。 神经发育障碍（NDD）由转录调节因子MECP 2突变引起。所以 该提案的总体目标是了解RTT的潜在病理生理学，并确定新的 治疗这种毁灭性疾病的方法Mecp 2突变小鼠（雄性无效小鼠和雌性杂合小鼠） 小鼠）表现出一系列的神经异常，这些神经异常概括了人类疾病，包括减少的 神经元树突复杂性和索马大小，以及严重的运动缺陷。重要的是，选择性地重新表达 Mecp 2在成年小鼠中的研究表明，RTT症状可以部分逆转，这表明， MeCP 2下游靶标的稳态也可以逆转或减轻RTT症状。 一种这样的潜在下游治疗靶标是NF-κB。我之前的研究表明 Mecp 2功能丧失的主要原因是Mecp 1的上调，导致NF-κB信号传导异常（Kishi* and MacDonald* 等人，Nature Communications 2016）。引人注目的是，在Mecp 2基因敲除雄性小鼠中遗传性降低NF-κB通路 部分挽救了他们减少的皮层树突复杂性，并大大延长了他们正常缩短的 寿命此外，我们的初步数据表明，膳食补充NF-κB抑制剂维生素 维生素D（VitD）部分挽救雄性小鼠Mecp 2-null表型。有趣的是，维生素D缺乏症非常普遍， 在RTT患者中，并且与多种其他NDD有关，包括自闭症谱系障碍（ASD）。 因此，我们推测，通过饮食中补充维生素D，NF-κB信号的减弱， 在RTT中的广泛治疗益处，以及潜在的具有重叠病理学的其他神经系统疾病。 我们建议通过比较维生素D补充剂的体内治疗潜力来验证我们的假设， 在雌性Mecp 2杂合子小鼠中NF-κB的遗传衰减（目的1），确定维生素D是否 补充剂通过细胞自主或细胞非自主来拯救RTT皮质神经元表型 机制（目标2），并确定这种表型拯救的潜在分子机制（目标3）。我们 将采取一种独特的，综合的方法，从分子（转录组）和 从细胞水平到神经元和树突的连接水平，再到行为。虽然维生素D补充剂可能 虽然没有提供RTT的“治愈”，但来自这种简单的、具有成本效益的补充剂的任何表型改善将 是非常令人兴奋的，具有改善生活质量的潜力。此外，我们将鉴定分子 支持表型改善的机制，这可能导致额外的新治疗靶点， 用于RTT和其他病理重叠的神经系统疾病。

PROJECT SUMMARY / ABSTRACT There is currently no effective treatment for Rett syndrome (RTT), a severe X-linked progressive neurodevelopmental disorder (NDD) caused by mutations in the transcriptional regulator MECP2. Hence, the overall goal of this proposal is to understand the underlying pathophysiology of RTT, and identify novel therapeutic avenues for this devastating disorder. Mecp2 mutant mice (male null mice, and female heterozygous mice) exhibit a range of neurological abnormalities that recapitulate the human disorder, including reduced neuronal dendritic complexity and soma size, and severe motor deficits. Importantly, selectively re-expressing Mecp2 in adult mice has shown that RTT symptoms can be partially reversed, suggesting that restoration of homeostasis of downstream targets of MeCP2 could also reverse or alleviate RTT symptoms. One such potential downstream therapeutic target is NF-κB. My previous work demonstrated that a consequence of Mecp2 loss of function is up-regulation of Irak1, leading to aberrant NF-κB signaling (Kishi* and MacDonald* et al, Nature Communications 2016). Strikingly, genetically reducing the NF-κB pathway in Mecp2-null male mice partially rescues their reduced cortical dendritic complexity and substantially extends their normally shortened lifespan. Further, our preliminary data demonstrate that dietary supplementation with the NF-κB inhibitor vitamin D (VitD) partially rescues Mecp2-null phenotypes in male mice. Intriguingly, VitD deficiency is highly prevalent in RTT patients, and has been implicated in multiple other NDDs, including autism spectrum disorders (ASD). We thus hypothesize that attenuation of NF-κB signaling, via dietary supplementation with VitD, could have broad therapeutic benefit in RTT, and potentially other neurological disorders with overlapping pathology. We propose to test our hypotheses by comparing the in vivo therapeutic potential of VitD supplementation and genetic attenuation of NF-κB in female Mecp2 heterozygous mice (Aim 1), determining whether vitamin D supplementation rescues RTT cortical neuronal phenotypes via cell autonomous or cell-non-autonomous mechanisms (Aim 2), and determining underlying molecular mechanisms of this phenotypic rescue (Aim 3). We will take a unique, integrative approach, investigating phenotypic rescue from the molecular (transcriptome) and cellular level, to the level of neuronal and dendritic connectivity, to behavior. Although VitD supplementation may not provide a “cure” for RTT, any phenotypic improvement from such a simple, cost-effective supplement would be extremely exciting, with the potential for quality of life improvements. Further, we will identify molecular mechanisms underpinning the phenotypic improvements, which could lead to additional new therapeutic targets, for RTT and other neurological disorders with overlapping pathology.