Polymorphism affecting water balance

多态性影响水平衡

• 批准号: 8394605
• 负责人: DAVID M COHEN
• 金额: --
• 依托单位: PORTLAND VA MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2014-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8394605
• 关键词: Accounting; Acids; Address; Adverse effects; Affect; Alleles; Amino Acids; Animal Model; Animals; Antidepressive Agents; Antipsychotic Agents; Back; Biological Assay; Blood Chemical Analysis; Body Water; Cations; Caucasians; Caucasoid Race; Chronic; Chronically Ill; Clinical; Code; Cognition; Complex; Controlled Study; DNA; Data; Data Set; Disease; Diuretics; Elderly; Electrolytes; Equilibrium; Ethnic Origin; Excretory function; Exhibits; Exons; Family; Genes; Genetic; Genetic Markers; Genetic Polymorphism; Genomics; Genotype; Germ Lines; Haplotypes; Heart; Heredity; Human; Hypernatremia; Hyponatremia; Hypothalamic structure; In Vitro; Individual; Individual Differences; Injection of therapeutic agent; Intervention; Introns; Investigation; Ion Channel; Knock-in Mouse; Life; Link; Linkage Disequilibrium; Mediating; Mediator of activation protein; Medical; Metabolism; Minority; Modeling; Mus; Mutation; Not Hispanic or Latino; Organism; Osmoregulation; Patients; Pharmaceutical Preparations; Phase; Phenotype; Physiological; Population; Population Study; Predisposing Factor; Predisposition; Prevalence; Process; Property; Proteins; RNA Splicing; Regulation; Regulator Genes; Reporter Genes; Risk; Role; Series; Serum; Severities; Signal Transduction; Single Nucleotide Polymorphism; Sodium; Spliced Genes; Stress; System; Testing; Transgenic Organisms; Tube; Variant; Veterans; Water; Water consumption; Wild Type Mouse; analog; animal data; arachidonate; base; blastocyst; case-based; cohort; collecting tubule structure; design; embryonic stem cell; falls; genetic regulatory protein; homologous recombination; human data; human subject; in vitro testing; in vivo; indexing; lipid mediator; member; mouse model; outcome forecast; promoter; receptor; recombinase; response; sensor; transmission process; vector

DESCRIPTION (provided by applicant): Disorders of water balance (i.e., hypernatremia and hyponatremia) are the most frequently encountered of the electrolyte problems; they are exceedingly common among the elderly, the acutely and chronically ill, and among patients taking certain diuretic and anti-depressant medications. All of these predisposing factors are present in a high percentage of patients served by the Department of Veterans Affairs. Aberrant water balance further complicates many chronic medical conditions and confers a poor prognosis independent of the severity of the underlying illness. Recent data from well-controlled studies indicate that even subtle abnormalities in systemic water balance can seriously affect coordination and cognition, and the propensity to falls. Regulation of body water balance is a complex process coordinated by the hypothalamus and executed by the kidney collecting duct; however, the central sensors of systemic tonicity had remained obscure. Recently, members of the transient receptor potential family of cation channels were proposed to serve this role, based upon extensive in vitro data and animal studies. We reasoned that a common single- nucleotide polymorphism in one of these genes may account for individual differences in systemic water balance among healthy elderly human subjects. We identified one such polymorphism in a key water- regulatory gene that confers an amino acid change and results in a protein with aberrant function in vitro. Importantly, we found that the presence of this polymorphism is strongly associated with hyponatremia in two healthy human populations. Furthermore, the effect size is large: the risk of hyponatremia is more than doubled by the presence of a single copy of this allele. To cement this relationship, we propose three experimental aims. In Aim I, we will sequence the haplotype block in which this polymorphism is embedded, to establish that no other polymorphism in tight linkage disequilibrium with our known variant accounts for the effect of this allele. Although we strongly suspect that this is the case, based upon our sequencing of all coding exons and splice junctions in this block, a robust conclusion requires phasing the entire haplotype block. This will also aid our investigation of multiple ethnicities. In Aim II, we will test additional large human populations for the presence of this polymorphism to confirm its association with serum sodium concentration and with hyponatremia. In Aim III, we will test for the role of epoxyeicosatrienoic acid signaling in systemic water balance in normal mice. Second, we will "knock in" the variant allele of the water-regulatory gene in a mouse model to test if it can independently recapitulate the human hyponatremic phenotype. We further propose to apply a number of physiological maneuvers to unmask a latent water-retentive phenotype. There is extremely high conservation between the human and mouse gene, including the amino acid affected by this polymorphism and its immediate context. Of note, we will not create a transgenic harboring an "extra" allele with this polymorphism; we will replace one or both wild-type alleles with a murine analog of this variant allele. In addition, in this Aim we will test the role of the epoxyeicosatrienoic acid system in regulating systemic water balance, in both wild-type and knock-in mice. There are no data addressing the role of this system in water balance in vivo, although it mediates tonicity-sensing by central osmosensing channels and we now show in our preliminary data that this effect is interrupted by our key polymorphism.

描述(由申请人提供)： 水平衡障碍(即高钠血症和低钠血症)是最常见的电解质问题；在老年人、急性和慢性病患者以及服用某些利尿剂和抗抑郁药物的患者中非常常见。所有这些诱因在退伍军人事务部提供服务的患者中占很高的比例。异常的水平衡使许多慢性疾病进一步复杂化，并导致预后不良，与潜在疾病的严重程度无关。最近来自控制良好的研究的数据表明，即使是全身水分平衡的微小异常也会严重影响协调和认知，以及摔倒的倾向。体内水分平衡的调节是一个复杂的过程，由下丘脑协调，由肾脏集合管执行；然而，全身紧张性的中枢感受器仍然不清楚。最近，基于大量的体外数据和动物研究，瞬时受体潜力阳离子通道家族的成员被提出发挥这一作用。我们推测，这些基因中的一个常见的单核苷酸多态可能解释了健康老年受试者体内水平衡的个体差异。我们在一个关键的水分调节基因中发现了一个这样的多态，它能在体外引起氨基酸变化，并导致蛋白质功能异常。重要的是，我们发现，在两个健康人群中，这种多态的存在与低钠血症密切相关。此外，影响的规模很大：该等位基因的单一副本的存在使低钠血症的风险增加了一倍以上。为了巩固这种关系，我们提出了三个实验目标。在目标I中，我们将对嵌入该多态的单倍型块进行测序，以确定与我们已知的变体紧密连锁不平衡的其他多态都不能解释该等位基因的影响。尽管我们强烈怀疑这种情况，但基于我们对该区块中所有编码外显子和剪接连接的测序，一个可靠的结论需要对整个单倍型区块进行分阶段。这也将有助于我们对多种族的调查。在AIM II中，我们将测试更多的人群中这种多态的存在，以确认它与血清钠浓度和低钠血症的相关性。在目标III中，我们将测试环氧二十碳三烯酸信号在正常小鼠全身水平衡中的作用。其次，我们将在小鼠模型中“敲入”水分调节基因的变异等位基因，以测试它是否能够独立地概括人类低钠血症的表型。我们进一步建议应用一些生理操作来揭示潜在的保水表型。人类和小鼠的基因之间有极高的保守性，包括受这种多态影响的氨基酸及其直接背景。值得注意的是，我们不会创建带有这种多态的“额外”等位基因的转基因；我们将用这种变异等位基因的小鼠类似物来替换一个或两个野生型等位基因。此外，在这一目标中，我们将在野生型和转基因小鼠身上测试环氧二十碳三烯酸系统在调节系统水平衡方面的作用。目前还没有关于这个系统在体内水分平衡中的作用的数据，尽管它通过中枢渗透感觉通道介导张力感觉，我们现在在我们的初步数据中表明，这种影响被我们的关键多态所打断。