Chloride homeostasis and GABA maturation in fragile X syndrome

脆性 X 综合征中氯离子稳态和 GABA 成熟

• 批准号: 9055846
• 负责人: Anis Contractor
• 金额: $ 23.18万
• 依托单位: NORTHWESTERN UNIVERSITY AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-25 至 2017-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9055846
• 关键词: 5' Untranslated Regions; Address; Adolescent; Affect; Autistic Disorder; Brain Diseases; Bumetanide; CGG repeat; Cells; Childhood; Chloride Ion; Chlorides; Development; Disease; Diuretics; Fragile X Mental Retardation Protein; Fragile X Syndrome; Genes; Homeostasis; Human; Hypermethylation; Inherited; Intellectual functioning disability; Interneurons; Knowledge; Lead; Link; Messenger RNA; MicroRNAs; Mus; Neurodevelopmental Disorder; Neurons; Neurotransmitters; Phenotype; Play; Polyribosomes; RNA-Binding Proteins; Regulation; Research; Role; Signal Transduction; Synapses; Testing; Translations; Validation; base; cell motility; critical period; effective therapy; excitatory neuron; gamma-Aminobutyric Acid; in vitro Assay; induced pluripotent stem cell; inhibitor/antagonist; insight; meetings; mouse model; neuron development; novel; postnatal; public health relevance; research study; response; sodium-potassium-chloride cotransporter 1 protein; synaptogenesis; transmission process; uptake

 DESCRIPTION (provided by applicant): Fragile X syndrome (FXS) is the most common form of inherited intellectual disability and also the single most common known cause of autism. FXS results from an expansion of a CGG repeat sequence in the 5' untranslated region of the gene, which causes hypermethylation, transcriptional silencing, and a resultant loss of expression of the Fragile X mental retardation protein (FMRP). FMRP is a polyribosome associated RNA binding protein that regulates the translation of a large number of messenger RNAs, has roles in mRNA transport, as well as regulating the expression of miRNAs. Altered trajectories for the maturation and stability of synapses have been observed in the cortex of the mouse model of FXS (Fmr1 ko). However, the underlying mechanisms of these alterations in cellular and synaptic development are unknown. One important regulator of cortical development is the inhibitory neurotransmitter GABA. During early development GABA responses in many cortical neurons are excitatory, only maturing to their inhibitory, hyperpolarizing type later. Excitatory effects of GABA have been demonstrated to be important for neuronal proliferation, cell migration, and synaptogenesis. In recent studies we discovered that the regulated development of hyperpolarizing GABA responses is delayed in the cortex of Fmr1 ko mice. We propose that this will lead to an alteration in GABA signaling that contributes to a delay in synaptic and cellular maturation in the cortex. The objectives of this proposal are twofold. The first is to determine how the efficacy of GABA signaling is altered during the critical period, and whether there is a causal link between delayed maturation of GABA signaling and delayed maturation of fast spiking interneurons. The second is to determine whether the underlying mechanism for these changes result from alterations in miRNA expression that normally regulate the transporters underlying the reversal potential for GABA. We will achieve these objectives using two specific aims. Aim 1 will test whether a commonly used diuretic bumetanide (which acts centrally to inhibit the juvenile chloride cotransporter, NKCC1) can rectify the changes in GABA responses and delayed maturation of fast spiking interneurons. In Aim 2 using in vitro assays combined with validation in mouse and human derived neurons we will determine whether several candidate miRNAs can regulate expression of the juvenile chloride cotransporter NKCC1, which sets the reversal potential for GABA. These studies will address important knowledge gaps and potentially provide novel insights into developing cures for FXS. Because similar abnormalities of neuron connectivity and synapse maturation are implicated in other childhood brain disorders, it is possible that this research will open new avenues of study in other disorders characterized by autism and intellectual disability.

 描述（由申请人提供）：脆性 X 综合征 (FXS) 是遗传性智力障碍的最常见形式，也是自闭症最常见的已知原因。 FXS 是由该基因 5' 非翻译区中 CGG 重复序列的扩展引起的，这会导致高甲基化、转录沉默，并导致脆性 X 智力迟钝蛋白 (FMRP) 表达丧失。 FMRP 是一种多核糖体相关 RNA 结合蛋白，可调节大量信使 RNA 的翻译，在 mRNA 运输以及调节 miRNA 的表达中发挥作用。在 FXS (Fmr1 ko) 小鼠模型的皮层中观察到突触成熟和稳定性的改变轨迹。然而，细胞和突触发育中这些改变的潜在机制尚不清楚。皮质发育的一种重要调节剂是抑制性神经递质 GABA。在早期发育过程中，许多皮质神经元的 GABA 反应是兴奋性的，后来才成熟为抑制性、超极化类型。 GABA 的兴奋作用已被证明对神经元增殖、细胞迁移和突触发生很重要。在最近的研究中，我们发现 Fmr1 ko 小鼠皮质中超极化 GABA 反应的调节发展被延迟。我们认为这将导致 GABA 信号传导的改变，从而导致皮质中突触和细胞成熟的延迟。该提案的目标是双重的。首先是确定 GABA 信号传导的功效在关键时期如何改变，以及 GABA 信号传导的延迟成熟与快速尖峰中间神经元的延迟成熟之间是否存在因果关系。第二个是确定这些变化的潜在机制是否是由 miRNA 表达的改变引起的，而 miRNA 表达通常调节 GABA 逆转潜力的转运蛋白。我们将通过两个具体目标来实现这些目标。目标 1 将测试常用的利尿剂布美他尼（其主要作用是抑制幼年氯协同转运蛋白 NKCC1）是否可以纠正 GABA 反应的变化和快速尖峰中间神经元的延迟成熟。在目标 2 中，我们将使用体外测定并结合小鼠和人源神经元的验证来确定几种候选 miRNA 是否可以调节幼年氯化物协同转运蛋白 NKCC1 的表达，该蛋白设定了 GABA 的逆转潜力。这些研究将弥补重要的知识空白，并有可能为开发 FXS 治疗方法提供新的见解。由于神经元连接和突触成熟的类似异常与其他儿童脑部疾病有关，因此这项研究可能会为以自闭症和智力障碍为特征的其他疾病的研究开辟新途径。