Investigating the homeostatic role of MeCP2 in mature brain

描述（由申请人提供）：Rett综合征（RTT）是一种几乎只影响女性的神经系统疾病，由编码甲基cpg结合蛋白2 （MECP2）的x连锁基因MECP2突变引起。患有RTT的婴儿在6-18个月之前表面上发育正常，但随后会退化，失去习得的运动和语言技能，并在他们的一生中逐渐发展出广泛的额外神经功能。是否需要MeCP2功能来实现和/或维持大脑中成熟的神经功能一直不清楚，但最近的一项研究表明，成年小鼠中MeCP2的再表达如何挽救疾病特征，这使得证据的平衡转向了MeCP2的“维持”作用。然而，一个有趣的未解决的问题是，MeCP2的早期表达是否仅通过出生后早期神经发育的关键时期，可能会改变随着蛋白质丢失而演变的疾病，这表明MeCP2在发育和神经成熟中的作用独立于其在维持中的作用。我假设MeCP2可能具有发育功能，并建议通过使用他莫昔芬诱导的Cre/loxP系统在成年小鼠中急性删除MeCP2来验证这一点。我预测，由于小鼠在出生后神经发育完成后将变为null，因此小鼠将出现一种RTT样综合征，该综合征只概括那些与需要MeCP2的维持功能相关的疾病特征，而不能概括与MeCP2发育或成熟要求相关的特征，从而为RTT的两种假设提供了明确的结论。小鼠将被表征为一般和行为表型（使用一系列已建立的小鼠生理和行为测试），中枢神经系统的神经病理变化，以及成人诱导的Mecp2基因敲除后关键脑区域的基因转录变化。初步数据证实了申请人设计的一种新型他莫昔芬给药方案的有效性，该方案可在成年（出生后60天）小鼠中97%的Mecp2等位基因重组，行为初步研究显示，成年诱导小鼠的行为发生了明显变化。完成的研究将探讨两个阶段的功能障碍是否与RTT有关，以及产后发育时期是否有可能改善RTT患者的预后。此外，基因转录的变化可能优先针对候选遗传途径进行治疗。

DESCRIPTION (provided by applicant): Rett Syndrome (RTT) is a neurological disorder almost exclusively affecting females and caused by mutations in the X-linked gene MECP2, which encodes methyl-CpG binding protein 2 (MeCP2). Infants with RTT experience ostensibly normal development until 6-18 months of age but then regress, losing learned motor and language skills and progressively developing a broad range of additional neurological features over the course of their life. Whether MeCP2 function is required either to achieve and/or to maintain mature neurological function in the brain has remained historically unclear, but a recent study demonstrating how reexpression of Mecp2 in adult null mice can rescue features of disease has shifted the balance of evidence in favor of a "maintenance" role for MeCP2. An interesting unanswered question, however, is whether early expression of MeCP2 only through the critical period of early post-natal neurological development might alter the disease that evolves following later loss of the protein, suggesting a role for MeCP2 in development and neurological maturation that is independent of its role in maintenance. I hypothesize that there likely are developmental functions of MeCP2 and propose to test this by acutely deleting Mecp2 in adult mice using the tamoxifen inducible Cre/loxP system. I predict that since mice will become null after post-natal neurological development has been completed, mice will develop a RTT-like syndrome that recapitulates only those disease features related to maintenance functions that require MeCP2 while failing to recapitulate features related to developmental or maturational requirements of MeCP2, thus providing definitive conclusions about the two hypotheses of RTT. Mice will be characterized for general and behavioral phenotypes (using a battery of established mouse physiological and behavioral tests), neuropathological changes in the central nervous system, and gene transcriptional changes in a key brain region following adult induced knockout of Mecp2. Preliminary data confirms the efficacy of a novel tamoxifen dosing regimen devised by the applicant for 97% recombination of the Mecp2 allele in adult (post natal day 60) mice and behavioral pilot studies reveal distinct behavioral changes in adult induced null mice. The completed studies will address whether two phases of dysfunction contribute to RTT and whether post-natal developmental periods might be targeted to improve the outcomes of RTT patients. Furthermore, gene transcriptional changes may prioritize targeting of candidate genetic pathways for therapy. PUBLIC HEALTH RELEVANCE: The causes of autism - a major public health concern - are likely many and are not totally clear at this time, but the cause of Rett syndrome (RTT), a disease with many features of autism, is known to be mutations in the gene MECP2 almost every time. In the present study, this knowledge will be employed to study RTT in mice, giving us an inroad into the enigmatic mechanisms of autism, which is expected to teach us more about both how RTT and related disorders like autism occur and how to improve these patients' lives through new therapy.