Diurnal Experimental Models to Investigate Neural Mechanisms of Sleep Disturbance in Smith-Magenis Syndrome

摘要 睡眠问题在许多神经发育障碍中是一种常见但未得到充分认识的共病。 值得注意的是，每4名神经发育障碍患者中就有1人出现睡眠节律紊乱。这些 睡眠问题似乎会加剧攻击性和自伤等不守规矩的行为，使生活变得非常 对病人和他们的家人来说都很困难。同时，大量的单基因致病基因 神经发育障碍编码转录和染色质调节。这些观察结果引发了 关于睡眠障碍和神经发育状况之间关系的基本问题。 睡眠障碍是大脑发育受损的结果，还是由昼夜节律失调引起的 控制日常节奏的时钟基因，包括睡眠/醒来周期？这种疾病是否与 转录调节因子直接控制神经发育基因的表达，上游时钟基因， 或者下游与睡眠有关的时钟靶基因？缺乏对这些问题的答案限制了循证 睡眠节律和神经发育受损的治疗策略。 模式生物是确定基因在神经发育和睡眠中的因果作用的必然工具 超出人类遗传和临床联系的干扰。然而，实验室的小鼠，主要是 哺乳动物是夜间活动的，即夜间活动，白天往往睡觉，而人类 是白天的。除了这种时型差异，大多数近亲交配的小鼠品系都不合成褪黑素，一种 睡眠和神经发育的关键调节剂。拟议的项目旨在通过以下方式克服这些缺点 建立日间实验系统以询问睡眠障碍的遗传机制 与神经发育受损有关。我们的靶基因是维甲酸诱导的1(RAI1)，其 杂合性是Smith-Magenis综合征(SMS)的致病因素。这种智力残疾综合症 白天昏昏欲睡，夜间清醒，并伴有血液倒置 褪黑激素循环。多个实验室培育出RAI1突变小鼠，但这些小鼠没有表现出睡眠节律 在短信患者中看到的干扰。RAI1编码与昼夜节律有关的组蛋白结合蛋白 Clock基因调控，但RAI1‘S在神经元昼夜节律基因调控中的作用尚不清楚。为了更好地 了解RAI1的作用，我们将采用两种方法-尼罗河草鼠，一种白天活动的啮齿动物，以及人类 来自胚胎干细胞的神经元。这项拟议的研究将提供第一个全天实验 研究短信病理生理学的系统和测试治疗干预措施的优秀平台 条件。许多治疗药物在夜间活动的啮齿动物模型中被证明有效，但在人类身上失败了 临床试验，可能是由于时型差异。因此，迫切需要一种日间实验。 所提出的方法可以应用于其他神经发育障碍，包括 睡眠障碍和其他。

Abstract Sleep problem is a common but underappreciated comorbidity in many neurodevelopmental disorders. Remarkably, >1 in 4 individuals with neurodevelopmental disorders exhibit sleep rhythm disturbance. These sleep problems appear to exacerbate unruly behavior such as aggression and self-injury, making life very difficult for patients and their families. Meanwhile, numerous causative genes for monogenic neurodevelopmental disorders encode transcriptional and chromatin regulators. These observations raise fundamental questions about the relationship between sleep disturbance and neurodevelopmental conditions. Is sleep disturbance a consequence of impaired brain development or caused by dysregulation of circadian clock genes that controls daily rhythms, including the sleep/wake cycle? Do the disease-associated transcriptional regulators directly control the expression of neurodevelopmental genes, upstream clock genes, or downstream clock-target genes involved in sleep? Lack of answers to these questions limits evidence-based therapeutic strategies for impaired sleep rhythm and neurodevelopment. Model organisms are inevitable tools to establish causal roles of genes in neurodevelopment and sleep disturbance beyond genetic and clinical associations in humans. However, the laboratory mice, the primary mammalian model, are nocturnal, i.e., active during the night and tend to sleep during the day, while humans are diurnal. In addition to this chronotype difference, most inbred mouse strains do not synthesize melatonin, a key modulator of sleep and neurodevelopment. The proposed project aims to overcome these shortcomings by generating the diurnal experimental systems to interrogate the genetic mechanisms of sleep disturbance associated with impaired neurodevelopment. Our target gene is retinoic-acid induced 1 (RAI1), whose heterozygosity is responsible for Smith-Magenis Syndrome (SMS). This intellectual disability syndrome involves sleepiness during the day and elevated awakeness during the night, accompanied by inverted blood melatonin cycles. Multiple laboratories generated Rai1-mutant mice, but the mice did not exhibit sleep rhythm disturbance as seen in SMS patients. RAI1 encodes a putative histone-binding protein implicated in circadian clock gene regulation, yet the RAI1's role in neuronal circadian gene regulation remains unknown. To better understand the roles of RAI1, we will employ two approaches ― Nile grass rat, a diurnal rodent, and human neurons derived from embryonic stem cells. The proposed research will provide the first diurnal experimental systems to study SMS pathophysiology and excellent platforms to test therapeutic interventions for this condition. Numerous therapeutic agents have proven effective in nocturnal rodent models failed in human clinical trials, likely due to the chronotype difference. Thus, there is an urgent need for a diurnal experimental system, and the proposed approaches can be applied to other neurodevelopmental disorders that involve sleep disturbance and beyond.