Comprehensive Deep Phenotyping and Multi-omics to Develop Clinical and Molecular Biomarkers for MeCP2-related Diseases

摘要 X连锁基因MECP 2（甲基CpG结合蛋白2）与两个主要的 神经发育障碍：Rett综合征（RTT），由MeCP 2的功能缺失突变引起，以及 MECP 2复制综合征（MDS），由过多的MeCP 2引起。RTT是一种最常见的遗传性 女性智力残疾的原因，而（MDS）是女性中最常见的基因重排之一。 男性。因为MeCP 2蛋白调节着大脑中数千个基因的表达， 地区，每种疾病的表型远远超出智力残疾，影响情绪，运动控制， 和自主功能1.大脑对MeCP 2的数量非常敏感：在24小时内， MeCP 2水平足以产生Rett样症状。这一事实对大多数人来说是一个突出的挑战。 正在为这些疾病开发有前途的疗法：通过增加RTT的治疗， MeCP 2水平过高会导致MDS;在MDS中抑制MeCP 2水平过高会导致RTT。避免 简单地将一组衰弱症状换成另一组，我们需要可靠的方法来衡量治疗 并评估我们是否给予了正确的剂量。 在人源化小鼠中的临床前研究已经令人信服地证明， (ASO)可以降低MeCP 2水平并逆转MDS表型;最近的工作鉴定了激酶， 磷酸酶调节MeCP 2的稳定性，同样在小鼠中具有良好的结果。这些选择都非常 有希望，但我们如何测量患者的MeCP 2水平？MeCP 2是一种核染色质结合蛋白 它在大脑中的表达水平非常高，无法直接测量。我们有 因此，我一直在寻找与MeCP 2水平相关但在血液中可测量的其他分子 样品或其他相对非侵入性的手段。我建议，对于RTT和MDS等复杂疾病， 复合生物标志物组将上级任何单一模式的措施，以判断治疗反应。我们 初步研究已经确定了两种重要的分子生物标志物， 在小鼠中;我们还有其他几个候选者。因此，本研究旨在开发一组临床 和分子生物标志物，将指导治疗工作，以防止过度或治疗不足，在这些 疾病德克萨斯州儿童医院拥有全国最大的RTT和MDS患者人群， 因此，我们有能力完成1）开发MDS的结局指标; 2）将表型与 Xq 28基因座的基因组结构;以及3）在人类中追踪变化的分子生物标志物 MeCP 2的水平。完成这三个目标将为ASO的临床试验奠定基础， MDS和铺平道路的研究涉及其他等位基因疾病涉及太多或太少的 相同的基因产物。

Abstract The X-linked gene MECP2 (methyl CpG-binding protein 2) is associated with two major neurodevelopmental disorders: Rett Syndrome (RTT), caused by loss-of-function mutations in MeCP2, and MECP2 duplication syndrome (MDS), caused by too much MeCP2. RTT is one of the most common genetic causes of intellectual disability in females, while (MDS) is one of the most common genomic rearrangements in males. Because the MeCP2 protein regulates the expression of thousands of genes across multiple brain regions, the phenotype of each disease extends well beyond intellectual disability to affect mood, motor control, and autonomic functions1. The brain is exquisitely sensitive to the quantity of MeCP2: a drop of just 16% in MeCP2 levels is enough to produce Rett-like symptoms. This single fact is a salient challenge to the most promising therapies being developed for these diseases: slightly over-shooting treatment for RTT by increasing MeCP2 levels too much will cause MDS; suppressing MeCP2 levels too much in MDS will cause RTT. To avoid simply exchanging one set of debilitating symptoms for another, we need reliable ways to measure treatment responses and to assess whether we are administering the correct dose. Preclinical studies in humanized mice have convincingly demonstrated that antisense oligonucleotides (ASO) can reduce MeCP2 levels and reverse the MDS phenotype; more recent work identified kinases and phosphatases that regulate MeCP2 stability, again with good results in mice. These options are both extremely promising, but how do we measure MeCP2 levels in patients? MeCP2 is a nuclear, chromatin-bound protein that is expressed at very high levels in the brain, where it is not accessible to direct measurement. We have therefore been searching for other molecules that correlate with MeCP2 levels but are measurable in blood samples or other relatively noninvasive means. I propose that, for such complex diseases as RTT and MDS, a composite biomarker panel will be superior to any single-modality measure to judge treatment response. Our preliminary studies have already identified two important molecular biomarkers that track with MeCP2 levels in mice; we have several additional candidates as well. This study therefore aims to develop a panel of clinical and molecular biomarkers that will guide therapeutic efforts to prevent over- or under-treatment in these diseases. Texas Children's Hospital has the largest patient populations in the country for both RTT and MDS, so we are well-positioned to accomplish 1) Develop outcome measures for MDS; 2) Correlate phenotypes with the genomic structure at Xq28 locus; and 3) Validate in humans molecular biomarkers that track with changes in MeCP2 levels in mice. Completing these three aims will lay the groundwork for clinical trials of ASOs in MDS and pave the path forward for studies involving other allelic disorders involving too much or too little of the same gene product.