Investigating a candidate therapeutic for Rett Syndrome

X染色体包含数百个疾病基因，与其相关的疾病主要影响 男性。然而，一个子集-包括神经发育障碍、Rett(RTT)、脆性X(FXS)和 CDKL5综合征--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 携带第二份X染色体，一种新的治疗策略已经重新唤醒健康的人 这种不活跃的X(Xi)上的等位基因可以逆转疾病症状。一个障碍是习受制于一个非常 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，我们实验室和其他团队最近的工作表明，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生物学的了解来开发XI- 重新激活毒品。RTT是一种严重的神经发育障碍，全世界约有1：10,000名女孩受到影响 世界。受影响的女孩遗传了一个甲基CpG结合蛋白2(MECP2)的缺陷拷贝，一种染色质- 对神经元发育至关重要的相关基因产物。RTT女孩出生正常，发育正常 通常在生命的最初几个月，但在6-12个月之间开始退化。RTT已关联 患有严重的自闭症和癫痫，是最令人衰弱的遗传性疾病之一。没有疾病- 目前的具体治疗，由于护理的标准只针对一般症状。在一个里程碑式的发现中 2007年，科学家在小鼠模型中证明了在RTT开始后恢复MECP2的表达 症状可以逆转神经系统疾病。因此，甲基氯化石蜡2的修复对 制药业。因为MECP2是一个X连锁基因，会导致X失活，而且几乎所有的患者 都是MECP2基因的杂合子，每个受影响的女孩在她生病的XI上都携带着MECP2的良好副本 细胞。我们的目标是解锁xi，恢复MECP2的表达。有来自基金会和 作为一项过期/不可续期的NIH拨款，我的实验室在过去的7年里一直在研究这个问题。对 测试XI-重新激活药物是RTT的雌性小鼠模型，因为现有的MeCP2+/-雌性小鼠具有 可变的疾病外显率，只是生命后期的一种轻微疾病，因此不适合作为 XI-重新激活平台。我们现在已经创造了一种新的携带野生型MeCP2的雌性RTT小鼠模型 XI表型复制了雄性RTT小鼠的严重疾病，因此是检测XI-1的理想模型。 重新激活候选药物。此外，我们已经确定了一种一流的混合模式药物，能够 在细胞模型中重新激活MECP2，最高可达30,000倍。我们建议的研究目标是：(I) (Ii)小鼠模型中PK/PD研究和临床前研究 体内潜在药物毒性的纵向评估，以及(Iii)新疾病疗效的测定- 相关动物模型。在为期5年的项目结束前，我们希望确保体内MECP2的概念验证 上调和表型拯救，并建立行业合作伙伴关系，为临床开发药物。

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.