Investigating a candidate therapeutic for Rett Syndrome

X染色体携带数百种疾病基因，其相关疾病主要影响 男性。然而，一个子集-包括神经发育障碍，Rett（RTT），脆性X（FXS）， CDKL 5 Syndrome-也影响或仅影响女性。自闭症是一种常见的表现。因为雌性细胞 携带X染色体的第二个副本，一种新兴的治疗策略是唤醒健康的人， 在该失活X（Xi）上的等位基因来逆转疾病症状。一个障碍是，Xi受到一个非常 强大的沉默机制，几十年来，人们认为Xi的重新激活是不可能的。 然而，我们实验室和其他小组最近的工作表明，Xi的重新激活是可以实现的。我们有 一直专注于Rett综合征（RTT），并利用我们对XCI生物学的理解来开发Xi- 重新激活药物RTT是一种严重的神经发育障碍，在整个欧洲影响约1：10，000的女孩。 世界受影响的女孩遗传了甲基CpG结合蛋白2（MECP 2）的一个缺陷拷贝， 相关的基因产物，对神经元发育至关重要。RTT女孩出生正常， 通常在出生后的最初几个月，但在6-12个月之间开始退化。RTT相关 患有严重的自闭症和癫痫，是最令人衰弱的遗传疾病之一。没有疾病- 目前的标准治疗仅针对一般症状。在一个里程碑式的发现中 2007年，科学家们在小鼠模型中证明，在RTT发作后恢复MECP 2表达， 症状逆转神经系统疾病。因此，MECP 2恢复是主要的兴趣， 医药行业。由于MECP 2是一个X-连锁基因，易受X-失活的影响，几乎所有患者 是杂合子的MECP 2基因，每个受影响的女孩携带一个良好的副本MECP 2对她生病的Xi 细胞我们的目标是解锁Xi并恢复MECP 2的表达。有了基金会的种子资金， 一个过期的/不可再生的NIH资助，我的实验室在过去的7年里一直致力于这个问题。的关键 测试Xi-再激活药物是RTT的雌性小鼠模型，因为现有的Mecp 2 +/-雌性小鼠具有 可变的疾病发病率，只有一个轻微的疾病，在以后的生活，因此不适合作为一个模型， Xi-激活平台。我们现在已经建立了一种新的携带野生型Mecp 2的雌性RTT小鼠模型， 该Xi表型模仿在雄性RTT小鼠中观察到的严重疾病，因此是用于测试Xi的理想模型。 重新激活候选药物。此外，我们已经确定了一流的混合模式药物， 在细胞模型中重新激活MECP 2高达30，000倍。我们的研究目标是（i） 在小鼠模型中优化和临床前开发先导候选物，（ii）PK/PD研究， 体内潜在药物毒性的纵向评价，和（iii）确定在新疾病中的功效- 相关动物模型。到5年项目结束时，我们希望能够确保体内MECP 2的概念验证 上调和表型拯救，并建立行业合作伙伴关系，以开发用于临床的药物。

The X-chromosome harbors hundreds of disease genes whose associated diseases predominantly affect males. However, a subset — including neurodevelopmental disorders, Rett (RTT), Fragile X (FXS), and CDKL5 Syndromes — also or only affects females. Autism is a frequent manifestation. Because female cells carry a second copy of the X-chromosome, an emerging treatment strategy has been to reawaken the healthy allele on this inactive X (Xi) to reverse disease symptoms. An obstacle has been that the Xi is subject to a very robust silencing mechanism and, for decades, it was thought that Xi-reactivation would not be possible. However, recent work from our lab and other groups indicates that Xi reactivation can be achieved. We have been focusing on Rett Syndrome (RTT) and leveraging our understanding of XCI biology to develop Xi- reactivating drugs. RTT is a severe neurodevelopmental disorder that affects ~1:10,000 girls throughout the world. Affected girls inherit one defective copy of methyl-CpG-binding protein 2 (MECP2), a chromatin- associated gene product that is crucial for neuronal development. RTT girls are born normal and develop normally for the first few months of life, but begin to regress between 6-12 months of age. RTT is associated with severe autism and seizures, and is one of the most debilitating genetic disorders. There is no disease- specific treatment at present, as the standard of care treats only general symptoms. In a landmark discovery of 2007, scientists demonstrated in a mouse model that restoring MECP2 expression after onset of RTT symptoms reverses the neurological disease. MECP2 restoration is therefore of major interest to the pharmaceutical industry. Because MECP2 is an X-linked gene subject to X-inactivation and nearly all patients are heterozygous for the MECP2 gene, every affected girl carries a good copy of MECP2 on the Xi of her sick cells. Our goal is to unlock the Xi and restore expression of MECP2. With seed funding from foundations and an expired/non-renewable NIH grant, my lab has worked on this problem for the past 7 years. Critical for testing Xi-reactivating drugs is a female mouse model for RTT, because existing Mecp2+/- female mice have variable disease penetrance, only a mild disease later in life, and are therefore not suitable as a model for the Xi-reactivation platform. We have now created a new female RTT mouse model that carries wildtype Mecp2 on the Xi, phenocopies the severe disease seen in male RTT mice, and is therefore an ideal model for testing Xi- reactivating drug candidates. Moreover, we have identified a first-in-class, mixed modality drug capable of reactivating MECP2 up to 30,000-fold in a cellular model. The goals of our proposed research are (i) optimization and preclinical development of the lead candidate in a mouse model, (ii) PK/PD studies and longitudinal evaluation of potential drug toxicities in vivo, and (iii) determination of efficacy in the new disease- relevant animal model. By the end of the 5-year project, we hope to secure proof-of-concept for in vivo MECP2 upregulation and phenotypic rescue, and establish industry partnerships to develop the drug for the clinic.