Respiratory Rhythmogenesis and Chemosensitivity: A Genomic Approach

描述(由申请人提供)： 呼吸节律生成是一个描述呼吸产生和模式随时间推移的过程的术语；异常节律生成会导致低氧和高碳酸血症的后果，导致睡眠呼吸暂停、心力衰竭、中风和其他慢性神经系统疾病的发病率。C57BL/6(B6)小鼠具有静止呼吸暂停和低氧后周期性呼吸(异常节律发生)的固有特征，定位于小鼠1号染色体~50Mb区域，我们称之为Stab1(代表稳定表型)QTL。下一步是进一步定义功能基因组元件。基于这些新的发现，假设稳定性表型(Stab1)的特征和基因与低氧和/或高二氧化碳反应相关，并且稳定性表型通过脑干回路表达。两个相互关联的目的是通过公共可获得的来自DBA和B6小鼠品系的重组近交系菌株(RISS)提供的机会来扩大表型和遗传图谱，以揭示Stab1和其他新基因在呼吸节律发生、呼吸模式和化疗敏感性中的功能。目的1)确定Stab1候选基因和功能蛋白：1)确定不稳定的表型特征(静息呼吸暂停1次/分钟和/或低氧2分钟后出现3次周期性呼吸)与RIS基因表达的相关性；2)比较研究结果与低氧、高碳酸血症的呼吸机反应性的关系。为了评估基因功能，我们将把RIS基因型与全球脑干mRNA的表达联系起来。这里的目的是利用这些已经具有SNP基因分型的RISS的力量，为SNPs与性状表达的虚拟QTL连锁创造机会，并使用全球mRNA表达(EQTL)和蛋白质组学来检验这一假说，识别参与呼吸节律发生的新的分子途径，并为人类的关联研究提供机会。目的2将在体外脑干切片中确定导致呼吸不稳定的机制。研究验证了这样的假设：1)对5-羟色胺激动剂和拮抗剂的反应，以及2)对阿片类药物、阿片类拮抗剂和NOS拮抗剂的反应将揭示不同菌株的动态行为和电路成分。其目的是利用B6不稳定性表型的发现作为一个平台，以确定基因组对呼吸稳定性和呼吸控制的总体贡献，长期目标是从机制上研究基因如何操作来产生异常的呼吸特征。这两个目标的结果将为候选基因的设计和排序、了解目前药物治疗的局限性以及将基因用作人类呼吸控制疾病的风险因素提供信息。

DESCRIPTION (provided by applicant): Respiratory rhythmogenesis is a term describing the processes for breath generation and patterning over time; abnormal rhythmogenesis carries consequences of hypoxia and hypercapnia, driving morbidity in conditions like sleep apnea, heart failure, stroke, and other chronic neurologic diseases. The C57Bl/6 (B6) mouse has inherent traits of pauses in breathing at rest and post-hypoxic periodic breathing (abnormal rhythmogenesis), localized to a ~50 Mb region on mouse Chromosome 1 which we call the Stab1 (for stability phenotype) QTL. The next step is to further define the functional genomic elements. Based on these novel findings, the hypotheses are that the stability phenotype (Stab1) trait and gene are correlated to hypoxic and/or hypercapnic responsiveness, and that the stability phenotype is expressed through brainstem circuits. Two interrelated aims expand the phenotype and genetic profiling through the opportunities afforded by publically available recombinant inbred strains (RISs) derived from DBA and B6 mouse strains in order to uncover the functions of Stab1 and other novel genes in respiratory rhythmogenesis, breath patterning, and chemosensitivity, in general. Aim 1 is designed to identify Stab1 candidate genes and functional proteins by 1) defining the association of the phenotypic trait of instability (number of pauses >1/minute during resting breathing and/or appearance of >3 cycles of periodic breathing following 2 minutes of hypoxia) with RIS genotypes relative to mRNA expression, and 2) comparing findings to hypoxic and and hypercapnic ventilatory responsiveness. To assess gene functions, we will link RIS genotype to global brainstem mRNA expression. The purpose here is to harness the power of these RISs which are already SNP genotyped, creating the opportunity for a virtual QTL linkage of SNPs to trait expression, and to use global mRNA expression (eQTL) and proteomics to test the hypothesis, identify novel molecular pathways involved in respiratory rhythmogenesis, and offer the opportunity for association studies in humans. Aim 2 will identify mechanisms producing breathing instability in in vitro brainstem slices. Studies test the hypotheses that 1) responses to serotonin agonists and antagonists and 2) responses to opiods, opiod antagonists, and NOS antagonists will disclose dynamic behaviors and circuit components which differ according to strain. The purpose is to utilize the discovery of the B6 instability phenotype as a platform to identify genomic contributions to breathing stability and respiratory control in general, with the long-term goal of mechanistically investigating how genes operate to produce abnormal ventilatory traits. Results from both Aims will inform the design of and priorities for sequencing of candidate genes, for understanding the current limitations of pharmacologic therapy, and for using genes as risk factors in human diseases of respiratory control.