Tetrahydrobiopterin Biosynthesis by Dopamine Neurons

描述（由申请人提供）：GTP环化水解酶I（GCH 1）催化黑质纹状体DA（NSDA）神经元内四氢生物蝶呤合成的第一步和限速步骤，四氢生物蝶呤是酪氨酸羟化酶和多巴胺（DA）产生的必需辅因子。一个完整的分析所需的基础和cAMP依赖性转录的GCH 1近端启动子的顺式作用元件是近和目标1是确定同源的GC盒结合蛋白，并确定其在基础和cAMP依赖性GCH 1转录的作用。由这些c/selements募集的反式作用因子也很重要，目的2的目标是在C/EBP β和NF-γ的磷酸化与cAMP依赖性GCH 1转录之间建立联系。关于NSDA神经元如何调节GCH 1基因的表达知之甚少。目的3是了解蛋白质启动子DNA相互作用的时间变化，发生在cAMP依赖的GCH 1转录NSDA神经元和测试的假设，GCH 1转录负耦合体树突D2自身受体的音调。GCH 1中的杂合突变可导致多巴反应性肌张力障碍（DRD），这是一种具有部分失稳的常染色体显性遗传疾病，选择性地减少NSDA神经元内的DA合成，并在儿童期表现为肌张力障碍，在成年期表现为帕金森病（PD）。一半的DRD患者在GCH 1开放阅读框中没有突变，并且推测在GCH 1基因调控区中有突变。因此，我们已经描述的保守基因组顺式元件可能是与GCH 1缺陷相关的突变位点。DRD患者未受影响的一级亲属的帕金森综合征发病率也是正常对照的23倍，这表明DRD，GCH 1和PD之间存在联系。假设GCH 1的背景遗传变异性可能促进家族性帕金森综合征和特发性PD的易感性，我们在目标4中提出对家族性帕金森综合征中GCH 1近端启动子和编码区的突变进行测序和功能表征。由于关联作图可能是识别遗传变异性的更有效策略，因此目标4中的其他研究将评估PD病例与对照组中GCH 1基因内的遗传变异性。目的5是确定人类GCH 1基因的遗传变异性是否影响GCH 1转录或GCH 1酶活性。我们希望这种多学科的方法将产生重要的新信息GCH 1在NSDA神经元功能的作用，并将导致一个新的理解DRD和家族性和特发性PD。

DESCRIPTION (provided by applicant): GTP cyclohydrolase I (GCH1) catalyzes the first and rate-limiting step in the synthesis of tetrahydrobiopterin, the essential cofactor for tyrosine hydroxylase and the production of dopamine (DA) within nigrostriatal DA (NSDA) neurons. A complete analysis of the cis-acting elements in the GCH1 proximal promoter necessary for basal and cAMP-dependent transcription is near and the goal of Aim 1 is to identify cognate binding proteins for the GC-box and determine their role in basal and cAMP-dependent GCH1 transcription. The trans-acting factors recruited by these c/selements are also important and the goal of Aim 2 is to forge a link between phosphorylation of C/EBPbeta and NF-Y and cAMP-dependent GCH1 transcription. Little is known about how NSDA neurons regulate GCH1 gene expression. The goal of Aim 3 is to understand the temporal changes in protein-promoter DNA interactions that take place during cAMP-dependent GCH1 transcription in NSDA neurons and to test the hypothesis that GCH1 transcription is negatively coupled to somatodendritic D2 autoreceptor tone. Heterozygous mutations in GCH1 can cause DOPA-responsive dystonia (DRD), an autosomal dominant disorder with partial penetrance that selectively decreases DA synthesis within NSDA neurons and presents in childhood as a dystonia and in adulthood as Parkinson's disease (PD). Half of DRD patients have no mutation in the GCH1 open reading frame and presumably have mutations in GCH1 gene regulatory regions. The conserved genomic cis-elements we have already described are therefore likely sites for mutations associated with GCH1 deficiency. Unaffected first-degree relatives of DRD patients are also known to have a 23-fold higher incidence of parkinsonism than do normal controls, suggesting a link between DRD, GCH1 and PD. With the hypothesis that background genetic variability in GCH1 may promote susceptibility to familial parkinsonism and idiopathic PD, we propose in Aim 4 to sequence and functionally characterize mutations in GCH1 proximal promoter and coding regions in familial parkinsonism. Because association mapping is potentially a more powerful strategy for identifying genetic variability additional studies in Aim 4 will assess genetic variability within the GCH1 gene in PD cases versus controls. The goal of Aim 5 is to determine whether genetic variability in the human GCH1 gene influences GCH1 transcription or GCH1 enzyme activity. We expect that this multidisciplinary approach will yield important new information on the role of GCH1 in NSDA neuron function and will lead to a new understanding of DRD and familial and idiopathic PD.