Biopterin Deficit in Schizophrenia: Genetic Dissection of BH4 Biosynthesis.

描述(申请人提供)：四氢生物蝶呤(BH4)是一种重要的辅因子，可维持多巴胺和5-羟色胺等胺类神经递质的可获得性，调节一氧化氮的合成，并刺激和调节谷氨酸能系统。神经递质系统调节失调与精神分裂症(SZ)的发病机制有关。基于BH4在NT合成中的中心作用，我们检测了大量SZ患者和对照受试者的血浆总生物蝶呤水平(BH4的测量)。与对照组相比，SZ患者组的生物蝶呤平均缺乏率高达34%。观察到的生物蝶呤缺乏症与报道的遗传性BH4缺乏症相当，支持其具有生理意义的特征。我们非常有意义的发现，以及：a)BH4在NT维持中的已知作用，b)在人和小鼠BH4缺乏症中观察到的CNS NT合成的失调，c)证据表明血浆生物蝶呤水平与CNS生物蝶呤水平相关，以及d)证据表明SZ患者尿生物蝶呤排泄没有增加，所有这些都支持我们的假设，即BH4生物合成失调参与了SZ的病因。SZ的易感性有很大的遗传成分，在另一项初步研究中，我们对BH4生物合成途径中的第一个基因GCH1进行了初步的基因测试，对132名受试者(86名SZ和46名对照组)进行了与SZ相关的多态基因分型。结果是惊人的：我们发现GCH1与SZ：优势比密切相关，P=0.0057。我们还发现，在SZ患者中，GCH1等位基因状态预示着低生物蝶呤水平。基于这些非常积极的初步数据，以及一些没有SZ相关GCH1基因的SZ受试者也存在生物蝶呤缺乏的事实，这项探索性研究旨在检验GCH1和其他BH4生物合成相关基因的DNA变异与生物蝶呤水平相关并影响生物蝶呤水平的假设，并且是SZ的候选易感基因。我们将使用重新测序阵列来筛选可能影响基因表达和/或蛋白质功能的DNA变异。在这项研究中产生的序列数据将被分析与低生物蝶呤水平和受试者诊断有关。这项拟议研究的具体目标是：目标1a。设计重新测序阵列，包括6个BH4生物合成途径基因的基因调控区、内含子-外显子边界和编码区，以及另外13个BH4调控相关基因。1B.以生成180名受试者(90名SZ受试者和90名对照)的基因序列数据，所有受试者都具有测定的血浆生物蝶呤水平。目的2.利用单标记关联检验和单倍型分析方法对测序数据进行分析，找出与SZ和生物蝶呤缺失相关的DNA变异。了解SZ生物蝶呤缺乏的遗传基础将是开发药物的主要依据，还可能允许进行症状前和早期诊断测试，以及可能改善SZ风险人群临床结果的早期治疗。7.项目叙述这项研究将测试精神分裂症(SZ)患者是否也在产生BH4的基因中存在DNA异常异常。精神分裂症患者体内一种名为BH4的化学物质水平异常低，这种化学物质对大脑功能非常重要。如果他们这样做了，我们将寻找治疗低BH4水平的方法，并试图通过这种方式改善患者的症状。我们还可能预测基因缺陷人群中SZ的风险，因此可能能够尽早开始治疗，以改善SZ患者和有SZ风险的年轻人的预后。

DESCRIPTION (provided by applicant): Tetrahydrobiopterin (BH4) is a vital cofactor that maintains availability of amine neurotransmitters including Dopamine and Serotonin, regulates Nitric Oxide synthesis, and stimulates and modulates the Glutamatergic system. Dysregulation of neurotransmitter (NT) systems has been implicated in the pathogenesis of schizophrenia (SZ). Based on the central roles of BH4 in NT synthesis, we assayed plasma total biopterin levels (a measure of BH4) in a large sample of patients with SZ and control subjects. A highly significant mean biopterin deficit of 34% was observed for the SZ patient group when compared to controls. The observed biopterin deficit is comparable to that reported for genetic BH4 deficiency disorders, supporting its characterization as having physiological significance. Our highly significant finding, along with: a) the known roles of BH4 in NT maintenance, b) dysregulation of CNS NT synthesis observed in human and mouse BH4 deficiencies, c) evidence that plasma biopterin levels are correlated with CNS biopterin levels, and d) evidence that urinary biopterin excretion is not increased in SZ, all support our hypothesis that dysregulation of BH4 biosynthesis is involved in the etiology of SZ. SZ susceptibility has a large genetic component, and in another preliminary study, we have performed initial genetic testing of GCH1, the first gene in the BH4 biosynthesis pathway, genotyping a polymorphism for association with SZ in a sample of 132 subjects (86 SZ and 46 control subjects). The results were striking: We found that GCH1 was strongly associated with SZ: odds ratio, 5.0, p= 0.0057. We also found that GCH1 allele status predicts low biopterin in SZ patients. Based on these very positive preliminary data, and the fact that some SZ subjects without the SZ-associated GCH1 genotype also have a biopterin deficit, this exploratory study is designed to test the hypothesis that DNA variants in GCH1 and other BH4 biosynthesis-related genes, are associated with and influence biopterin levels, and are candidate SZ susceptibility loci. We will employ Re- Sequencing Arrays to screen for DNA variants that may influence gene expression and/or protein function. Sequence data generated in this study will be analyzed for association with low biopterin levels and subject diagnosis. The Specific aims of this proposed study are: Aim 1a. To design Re-Sequencing arrays that include the gene regulatory regions, intron-exon boundaries, and coding regions for the six BH4 biosynthesis pathway genes, plus 13 additional BH4 regulation-associated genes. 1b. To generate gene sequence data for 180 subjects (90 SZ subjects and 90 controls), all with assayed plasma biopterin levels. Aim 2. To analyze the sequence data using single marker association testing and haplotype analyses, and to identify DNA variants associated with SZ and biopterin deficit. Understanding the genetic basis of the SZ biopterin deficit will be primary to development of medications and may also allow pre-symptomatic and early diagnostic testing, and early treatment that may improve the clinical outcomes for persons at risk of developing SZ. 7. PROJECT NARRATIVE This study will test whether people with schizophrenia (SZ), who showed abnormally low levels of a chemical called BH4 that is very important for brain function, also have DNA abnormalities in the genes that produce BH4. If they do, we will look for ways to treat low BH4 levels, and try to improve the symptoms of patients that way. We may also be able to predict risk of SZ in people with the gene defect, and therefore may be able to start treatment as early as possible to improve the outcome for those with the disease and young people at risk of developing SZ.