Glial chemosensitivity and control of breathing in Rett syndrome

雷特综合征中胶质细胞的化学敏感性和呼吸控制

• 批准号: 10548130
• 负责人: DANIEL K MULKEY
• 金额: $ 53.28万
• 依托单位: UNIVERSITY OF CONNECTICUT STORRS
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-01 至 2024-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10548130
• 关键词: Affect; Animal Model; Animals; Astrocytes; Behavior; Brain; Brain Stem; Brain region; Breathing; Carbon Dioxide; Cell Nucleus; Cessation of life; Communication; Data; Electrophysiology (science); Elements; Extracellular Space; Failure; Genes; Goals; Grant; Homeostasis; In Vitro; Ions; Knockout Mice; Link; Measurement; Mediating; Membrane Potentials; Methyl-CpG-Binding Protein 2; Molecular; Morphology; Mus; Mutation; Neurodevelopmental Disorder; Neurons; Online Mendelian Inheritance In Man; Patients; Phenotype; Plethysmography; Process; Quality of life; Reflex action; Regulation; Respiration Disorders; Rett Syndrome; Role; Seizures; Site; Sleep; Slice; Symptoms; Testing; Tissues; Viral; Wakefulness; Work; autistic behaviour; comorbidity; extracellular; human model; improved; in vivo; insight; loss of function mutation; mortality; mouse model; novel; patient population; premature; respiratory; response; targeted treatment; therapeutic target

SUMMARY Rett syndrome (RTT) (OMIM #312750) is a severe X-linked neurodevelopmental disorder caused by mutations in the methyl-CpG-binding protein 2 (MECP2). Although RTT patients suffer from many co-morbid phenotypes, wake disordered breathing has a major negative impact quality of life and is associated with high mortality rate in this patient population. Evidence from murine models of RTT suggest disordered breathing results in part from a disrupted ability to regulate breathing in response to changes in tissue CO2/H+ (i.e., central chemoreflex). The retrotrapezoid nucleus (RTN) is a critical chemosensitive brainstem nucleus, contains CO2/H+-sensitive neurons and astrocytes that together produce a CO2/H+-dependent drive to breath. Previous and preliminary data identify heteromeric Kir4.1/5.1 channels as key determinants of RTN astrocyte CO2/H+ chemosensitivity. However, homomeric Kir4.1 and heteromeric Kir4.1/5.1 are differentially CO2/H+ sensitive and regulate divergent astrocyte processes including membrane potential and clearance of neuronally released extracellular K+, and it is not clear which of these mechanisms contributes to RTN chemoreception and disordered breathing in RTT. Our previous work showed that MeCP2 deficient mice have reduced levels of Kir4.1 and 5.1 channels, diminished astrocytic Kir4.1/5.1-like currents, dysregulated extracellular K+. MeCP2 deficient mice also show a blunted ventilatory response to CO2. Similarly, preliminary results show that global deletion of astrocyte Kir4.1 channels also blunts the ventilatory response to CO2. Importantly targeted (re)expression of Kir4.1 specifically in RTN astrocytes rescued disordered breathing in both Kir4.1 cKO and MeCP2 deficient mice. Preliminary data also show that RTN astrocytes from Kir5.1 KO animals lack CO2/H+ sensitivity, thus suggesting heteromeric Kir4.1/5.1 channels regulate RTN astrocyte chemosensitivity. Recent ultrastructural studies indicate reduced astrocytic coverage of neuronal elements during sleep together with increased extracellular space; thus necessitating state-dependent changes in astrocyte ion and transmitter homeostasis, that may account for a reduced ventilatory response to CO2 during sleep. Consistent with this, preliminary results show that RTN astrocytes undergo a ~25% volume increase in the wake state as compared to sleep. Based on this, we hypothesize that Kir4.1/5.1 deficiency and compromised astrocyte chemoreception are responsible for state-dependent disordered breathing in RTT. In this proposal, we use an established mouse model of RTT, an inducible astrocyte specific Kir4.1 knockout mouse in conjunction with astrocyte targeted AAV, astrocyte volume and morphological complexity measurements, slice electrophysiology, and whole-animal plethysmography to explore the sleep-wake state-dependent contributions of Kir4.1/5.1 channels to RTN chemoreception and respiratory activity in RTT. Understanding how Kir4.1 and Kir5.1 contribute to RTN chemoreception across sleep-wake states and disordered breathing may provide mechanistic insight for targeted treatment of disordered breathing in RTT.

概括 Rett 综合征 (RTT) (OMIM #312750) 是一种由突变引起的严重 X 连锁神经发育障碍 存在于甲基 CpG 结合蛋白 2 (MECP2) 中。尽管 RTT 患者患有许多共病表型， 清醒时呼吸紊乱对生活质量产生重大负面影响，并与高死亡率相关 在这个患者群体中。来自 RTT 小鼠模型的证据表明呼吸紊乱在一定程度上会导致 因组织 CO2/H+（即中枢神经系统）变化而调节呼吸的能力受到破坏 化学反射）。梯形后核（RTN）是一个关键的化学敏感性脑干核，包含 CO2/H+ 敏感神经元和星形胶质细胞共同产生 CO2/H+ 依赖性呼吸驱动。以前的 初步数据确定异聚 Kir4.1/5.1 通道是 RTN 星形胶质细胞 CO2/H+ 的关键决定因素 化学敏感性。然而，同聚体 Kir4.1 和异聚体 Kir4.1/5.1 对 CO2/H+ 的敏感性不同 并调节不同的星形胶质细胞过程，包括膜电位和神经元清除 释放细胞外 K+，目前尚不清楚这些机制中哪一种有助于 RTN 化学感受 RTT 中呼吸紊乱。我们之前的工作表明 MeCP2 缺陷小鼠的水平降低 Kir4.1 和 5.1 通道的缺失，星形胶质细胞 Kir4.1/5.1 样电流减少，细胞外 K+ 失调。甲基CP2 缺陷小鼠还表现出对二氧化碳的通气反应迟钝。同样，初步结果表明，全球 星形胶质细胞 Kir4.1 通道的缺失也会减弱对 CO2 的通气反应。重点针对性 在 RTN 星形胶质细胞中特异地（重新）表达 Kir4.1 可挽救 Kir4.1 cKO 和 Kir4.1 cKO 中的呼吸紊乱 MeCP2 缺陷小鼠。初步数据还表明，来自 Kir5.1 KO 动物的 RTN 星形胶质细胞缺乏 CO2/H+ 敏感性，因此表明异聚 Kir4.1/5.1 通道调节 RTN 星形胶质细胞的化学敏感性。 最近的超微结构研究表明，一起睡觉时星形胶质细胞对神经元元素的覆盖减少 细胞外空间增加；因此需要星形胶质细胞离子和递质发生状态依赖性变化 体内平衡，这可能是睡眠期间对二氧化碳的通气反应减少的原因。与此相一致的是， 初步结果表明，与清醒状态相比，RTN 星形胶质细胞的体积增加了约 25% 睡觉。基于此，我们假设 Kir4.1/5.1 缺陷和星形胶质细胞受损 化学感受是 RTT 中状态依赖性呼吸紊乱的原因。在这个提案中，我们 使用已建立的 RTT 小鼠模型，结合诱导型星形胶质细胞特异性 Kir4.1 敲除小鼠 星形胶质细胞靶向 AAV、星形胶质细胞体积和形态复杂性测量、切片 电生理学和全动物体积描记法探索睡眠-觉醒状态依赖性 Kir4.1/5.1 通道对 RTT 中 RTN 化学感受和呼吸活动的贡献。理解 Kir4.1 和 Kir5.1 如何在睡眠-觉醒状态和呼吸紊乱状态下促进 RTN 化学感受 可能为 RTT 呼吸障碍的靶向治疗提供机制见解。