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.

总结 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 甲基CpG结合蛋白2（MECP2）尽管RTT患者患有许多共病表型， 唤醒呼吸紊乱对生活质量有重大的负面影响，并与高死亡率相关 在这个病人群体中。来自RTT小鼠模型的证据表明，呼吸障碍部分导致 由于响应组织CO2/H+变化而调节呼吸的能力被破坏（即，中央 化学反射）。后斜方核（RTN）是脑干化学敏感的重要核团， 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。先前 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 化疗敏感性然而，同聚Kir4.1和异聚Kir4.1/5.1对CO2/H+的敏感性不同 并调节星形胶质细胞的分化过程，包括膜电位和神经元的清除。 释放细胞外K+，但尚不清楚这些机制中的哪一个有助于RTN化学感受 和呼吸紊乱我们以前的工作表明，MeCP2缺陷小鼠的水平降低， Kir4.1和5.1通道，减少星形胶质细胞Kir4.1/5.1样电流，失调的细胞外K+。MeCP2 缺陷型小鼠对CO2也表现出迟钝的呼吸反应。同样，初步结果显示，全球 星形胶质细胞Kir4.1通道的缺失也减弱了对CO2的反应。重要目标 Kir4.1在RTN星形胶质细胞中的特异性（重新）表达挽救了Kir4.1 cKO和 MeCP2缺陷小鼠。初步数据还显示，来自Kir5.1 KO动物的RTN星形胶质细胞缺乏CO2/H + 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，在一起睡眠期间，星形胶质细胞神经元元件的覆盖减少 随着细胞外空间的增加;因此需要星形胶质细胞离子和递质的状态依赖性变化 内稳态，这可能是睡眠期间对CO2的呼吸反应降低的原因。与此相一致， 初步结果显示，与对照组相比，RTN星形胶质细胞在唤醒状态下体积增加约25%。 睡吧基于此，我们假设Kir4.1/5.1缺陷和受损的星形胶质细胞 化学感受是RTT中状态依赖性呼吸紊乱的原因。在本提案中，我们 使用已建立的RTT小鼠模型，可诱导星形胶质细胞特异性Kir4.1敲除小鼠， 使用星形胶质细胞靶向AAV、星形胶质细胞体积和形态复杂性测量，切片 电生理学和整体动物体积描记法来探索睡眠-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中促进RTN化学感受 可能为RTT中呼吸障碍的靶向治疗提供机制见解。