Blood Genomics and Cell Model Approaches for Neuropsychiatric Disorders

最近发现的一个通过D2受体参与多巴胺胞内信号传导的基因是AKT1 （v-akt小鼠胸腺瘤病毒癌基因同源物1）。在精神分裂症患者死后前额叶皮层的B淋巴细胞中观察到AKT1蛋白水平降低，进一步表明这些发现与精神病的病理生理学有关。先前有几项研究表明AKT1与精神分裂症有关；然而，与单核苷酸多态性（snp）相关的风险在不同的研究中有所不同。我们假设，如果多巴胺能信号受到AKT1的影响，那么AKT1的遗传变异将与大脑皮层多巴胺能功能相关的表型相关，类似于上述基因的观察结果。我们对AKT1中的几个snp进行了基因分型，但重点研究了一个编码变异，该变异已被证明会影响人类B淋巴细胞的蛋白质表达和对辐射诱导的细胞凋亡的敏感性。我们证实了报告的对正常对照B淋巴细胞中AKT1蛋白水平的影响。GCAP的其他小组也发现了与多巴胺功能相关的几种脑测量的关联，包括与额纹状体回路相关的认知表现，功能性磁共振成像（fMRI）测定执行功能时的前额叶效率，以及MRI上的额纹状体灰质体积。有初步证据表明COMT的多种细胞效应可能涉及其他基本分子机制，我们对nrg1诱导的B淋巴细胞迁移的研究发现COMT val/met基因型对迁移和AKT1磷酸化有影响（Sei等）。， PloS One, 2010)。我们在nrg1刺激的B淋巴母细胞系统中研究了AKT1的激活，并研究了COMT和AKT1之间的功能相互作用。nrg1诱导的AKT1磷酸化分析显示，与携带met等位基因的个体相比，COMT val个体的磷酸化水平降低。在这项研究中，我们发现AKT1 （rs1130233）和COMT val108/158met基因型的功能编码多态性在AKT1激活的细胞过程中存在显著的相互作用。数据表明，通过s -腺苷甲硫氨酸（SAM）与磷脂酰丝氨酸（PS）合成竞争，COMT酶活性影响AKT1的功能，而s -腺苷甲硫氨酸（SAM）调节AKT1依赖的细胞对nrg1介导的信号传导的反应。由于COMT与其他甲基化酶竞争广泛使用的甲基供体SAM，它也可能间接影响DNA甲基化。我们正在与其他团队合作，在我们的淋巴细胞中进行靶向基因甲基化测定。这些发现增加了COMT在精神分裂症神经生物学中的作用；COMT和AKT1之间的遗传和功能相互作用可能为精神分裂症的发病机制提供新的见解。

A gene recently implicated in dopamine intracellular signaling through D2 receptors is AKT1 (v-akt murine thymoma viral oncogene homolog 1). Decreased AKT1 protein levels have been observed in B lymphoblasts in the postmortem prefrontal cortices of patients with schizophrenia furthering the possibility that these findings relate to the pathophysiology of psychosis. Several studies had previously shown association of AKT1 with schizophrenia; however, the risk associated single nucleotide polymorphisms (SNPs) varied across studies. We hypothesized that if dopaminergic signaling is impacted by AKT1, then genetic variation in AKT1 would be associated with brain phenotypes related to cortical dopaminergic function, analogous to those observed with the genes described above. We genotyped several SNPs in AKT1 but focused on a coding variation which had been shown to affect protein expression in human B lymphoblasts and sensitivity to radiation induced apoptosis. We confirmed the reported effect on AKT1 protein levels in B lymphoblasts from our normal controls. Other groups in GCAP also found associations with several brain measures related to dopamine function, including cognitive performance linked to frontostriatal circuitry, prefrontal efficiency during executive function assayed with functional magnetic resonance imaging (fMRI), and frontostriatal gray matter volume on MRI. Having preliminary evidence that the diverse cellular effects of COMT may involve additional basic molecular mechanisms, our study of NRG1-induced B lymphoblast migration found effects of COMT val/met genotype on migration and also on phosphorylation of AKT1 (Sei et.al., PloS One, 2010). We studied AKT1 activation in our NRG1-stimulated B lymphoblasts cell system and studied a functional interaction between COMT and AKT1. The analysis of NRG1-induced AKT1 phosphorylation showed reduced phosphorylation in COMT val individuals compared with those carrying the met allele. In this study, we showed a significant interaction of a functional coding polymorphism in AKT1 (rs1130233) and COMT val108/158met genotype on the cellular process of AKT1 activation. The data suggest that AKT1 function is influenced by COMT enzyme activity through competition with phosphatidylserine (PS) synthesis through S-adenosylmethionine (SAM), which regulates AKT1-dependent cellular responses to NRG1-mediated signaling. Because COMT competes with other methylases for the widely used methyl donor, SAM, it may also impact indirectly on DNA methylation. We are working in collaboration with other groups to do targeted gene methylation assays in our lymphocytes. These findings add to the role of COMT in the neurobiology of schizophrenia; the genetic and functional interactions between COMT and AKT1 may provide novel insight into the pathogenesis of schizophrenia.