Circadian and Sleep Programming in Angelman Syndrome Mouse Models

项目摘要/摘要： 昼夜节律调节无数的行为和分子过程，包括运动活动， 睡眠时间、摄食行为、新陈代谢和基因表达。这些生物“时钟”是至关重要的 人类健康的组成部分，而这一系统的不正常功能与睡眠/清醒障碍有关， 代谢综合征和肥胖症。生物钟机制的当前分子模型包括 中枢时钟基因的自动调节转录和翻译反馈环需要节律性 时钟基因产物的合成和降解。我们发现Ube3a的有效基因剂量 编码泛素连接酶(参与蛋白质降解)的基因调节着 哺乳动物的生物钟系统。 Ube3a基因的表达水平对正常的神经发育至关重要。例如，减少了 Ube3a的剂量会导致Angelman综合征(AS)，而剂量/活性的增加会导致自闭症。 因此，Ube3a的表达水平对正常的认知发育至关重要，本论文 项目是Ube3a的平衡表达也是稳定的昼夜节律性的关键。因为这是一种混乱 以认知/发育迟缓、言语障碍、睡眠障碍和癫痫为特征。这个 父亲的Ube3a等位基因在神经元中被印记(沉默)，大多数AS病例是由于缺失了Ube3a 母体Ube3a等位基因进一步下调神经元中的Ube3a。已经产生了小鼠模型， 有(I)母体Ube3a等位基因的缺失(AS模型)，和(Ii)额外的Ube3a副本(孤独症模型)； 这些模型验证了我们的假设，即ube3a的表达影响昼夜节律的可塑性。 节律，以及环境、遗传和/或药物治疗可以被确定为补偿 对于Ube3a表达式的丢失。这一假设将通过操纵环境、遗传和 发育条件对AS小鼠模型昼夜节律系统的影响。特定药理作用 将测试治疗方法在逆转AS模型昼夜节律表型方面的潜力，以用作 用于确定用于人类受试者的生物标记物的基础。时钟蛋白将被鉴定为分子 Ube3a介导的泛素化的靶点。最后，将测试Ube3a过度表达的小鼠模型 确定Ube3a过度表达是否会对AS模型的Ube3a空值产生互惠影响。 这个项目代表了一个新的调查领域，有可能加强与健康相关的 研究；它的总体意义是(I)阐明泛素化和印记在昼夜节律中的作用 机制，以及(Ii)确定改善小鼠Ube3a印迹昼夜节律紊乱的治疗方法 模特们。这些问题的答案将有助于我们理解基本的昼夜节律组织和 在这个令人着迷的-并且潜在的临床相关的-X基因环境相互作用的例子中的可塑性。

Project Summary/Abstract: Circadian (daily) rhythms regulate myriad behavioral and molecular processes including locomotor activity, sleep timing, feeding behavior, metabolism, and gene expression. These biological "clocks" are a crucial component of human health, and improper functioning of this system is associated with sleep/wake disorders, metabolic syndrome, and obesity. The current molecular model for the circadian clock mechanism comprises autoregulatory transcriptional & translational feedback loops of central clock genes that necessitate rhythmic synthesis and degradation of clock gene products. We have found that the effective gene dosage of the Ube3a gene that encodes an ubiquitin ligase (involved in protein degradation) regulates fundamental properties of the circadian clock system in mammals. The expression level of the Ube3a gene is crucial for normal neurodevelopment. For example, reduced dosage of Ube3a leads to Angelman Syndrome (AS) and increased dosage/activity can result in autism. Therefore, the level of expression of Ube3a is critical for normal cognitive development, and the thesis of this project is that balanced expression of Ube3a is key for stable circadian rhythmicity as well. AS is a disorder characterized by cognitive/developmental delays, speech impairment, sleep disorders, and seizures. The paternal allele of Ube3a is imprinted (silenced) in neurons, and most cases of AS result from a deletion of the maternal Ube3a allele that further downregulates Ube3a in neurons. Mouse models have been generated that have (i) a deletion of the maternal Ube3a allele (model of AS), and (ii) extra copies of Ube3a (model of autism); these models enable tests of our hypothesis, which is that Ube3a expression affects the plasticity of circadian rhythms and that environmental, genetic, and/or pharmacological treatments can be identified that compensate for the loss of Ube3a expression. This hypothesis will be tested by manipulating environmental, genetic, and developmental conditions to affect the circadian system in mouse models of AS. Specific pharmacological treatments will be tested for their potential in reversing the circadian phenotypes of AS models to use as a basis for identifying a biomarker to be used with human subjects. Clock proteins will be identified as molecular targets of Ube3a-mediated ubiquitination. Finally, an Ube3a overexpressing mouse model will be tested to determine if Ube3a overexpression has reciprocal effects to the Ube3a null of AS models. This project represents a novel area of investigation that has the potential to enhance health-related research; its overall significance is (i) to elucidate the role of ubiquitination and imprinting in the circadian mechanism, and (ii) to identify treatments that ameliorate the circadian disorders of Ube3a imprinting in mouse models. The answers to these questions will help us to understand fundamental circadian organization and plasticity in this fascinating–and potentially clinically relevant–example of gene X environment interaction.