Contributions of Astrocyte Kir4.1/5.1 Channels to Disordered Breathing in Rett Syndrome

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（MECP 2）尽管RTT患者患有许多共病表型， 苏醒期呼吸紊乱对生活质量具有主要的负面影响，并且与高死亡率相关。 来自RTT小鼠模型的证据表明，呼吸障碍部分是由于呼吸能力受到干扰， 响应于组织CO2/H+的变化调节呼吸（即，中枢化学反射）。后梯形 核（RTN）是化学感受的重要部位，该区域的神经元和星形胶质细胞感受化学感受的变化。 CO2/H+调节呼吸。以前的工作确定异聚Kir4.1/5.1通道是细胞增殖的关键决定因素。 RTN星形胶质细胞CO2/H+化学敏感性。然而，同聚Kir4.1和异聚Kir4.1/5.1是 差异CO2/H+敏感和调节分歧星形胶质细胞过程，包括膜电位， 清除神经元释放的细胞外K+，目前尚不清楚这些机制中的哪一个有助于 RTN化学感受和RTT呼吸障碍。我的赞助商小组以前的工作表明， MeCP 2缺陷小鼠的Kir4.1和5.1通道水平均降低，星形胶质细胞Kir4.1 介导的电流和失调的细胞外K+。初步数据还显示，Kir4.1的整体缺失 星形胶质细胞的Kir4.1表达减弱了对CO2的反应，而Kir4.1在RTN中的特异性重新表达 星形胶质细胞拯救了这种呼吸表型。基于此，我假设MeCP 2缺乏导致 Kir4.1/5.1缺失和星形胶质细胞化学感受受损导致呼吸紊乱 RTT。为了探索这种可能性，我将测试以下两个具体目标：1）确定星形胶质细胞的作用 Kir4.1通道在体外RTN化学感受中的作用; 2）鉴定Kir4.1和Kir5.1的不同作用 在RTT中控制呼吸的通道。了解Kir4.1和Kir5.1对RTN的贡献 化学感受和呼吸紊乱可能为靶向治疗呼吸紊乱提供机制性见解。 呼吸RTT。这项工作也将提供宝贵的培训机会，在分子，细胞和整体- 动物的方法，这将为我在科学界的成功未来做好准备。

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. Evidence from mouse 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 an important site of chemoreception, neurons and astrocytes in this region sense changes in CO2/H+ to regulate breathing. Previous work identifies 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. Previous work from my sponsors group showed that MeCP2 deficient mice have reduced levels of both Kir4.1 and 5.1 channels, diminished astrocytic Kir4.1 mediated currents and dysregulated extracellular K+. Preliminary data also show that global deletion of Kir4.1 from astrocytes blunts the ventilatory response to CO2, while re-expression of Kir4.1 specifically in RTN astrocytes rescued this respiratory phenotype. Based on this, I hypothesize that MeCP2 deficiency results in loss of Kir4.1/5.1 and compromised astrocyte chemoreception that contributes to disordered breathing in RTT. To explore this possibility, I will test the following two Specific Aims: 1) Determine roles of astrocyte Kir4.1 containing channels in RTN chemoreception in vitro; and 2) Identify differential roles of Kir4.1 and Kir5.1 channels in the control of breathing in RTT. Understanding how Kir4.1 and Kir5.1 contribute to RTN chemoreception and disordered breathing may provide mechanistic insight for targeted treatment of disordered breathing in RTT. This work will also provide valuable training opportunities in molecular, cellular and whole- animal approaches that will prepare me for a successful future in science.