Blood Genomics and Cell Model Approaches for Neuropsychiatric Disorders

最近通过D2受体参与多巴胺细胞内信号转导的基因是AKT1(v-AKT小鼠胸腺瘤病毒癌基因同源1)。在精神分裂症患者死后额叶皮质的B淋巴母细胞中观察到AKT1蛋白水平降低，进一步表明这些发现可能与精神病的病理生理学有关。此前已有多项研究表明AKT1与精神分裂症有关；然而，风险相关单核苷酸多态(SNPs)在不同研究中有所不同。我们假设，如果多巴胺能信号受到AKT1的影响，那么AKT1的遗传变异将与与皮质多巴胺能功能相关的大脑表型相关，类似于上述基因所观察到的。我们对AKT1中的几个SNPs进行了基因分型，但重点放在一个编码变异上，该变异已被证明会影响人类B淋巴母细胞的蛋白表达，并影响对辐射诱导的细胞凋亡的敏感性。我们证实了报道的对正常对照组B淋巴母细胞AKT1蛋白水平的影响。GCAP中的其他小组也发现了与多巴胺功能相关的几项大脑指标的相关性，包括与额纹状体回路有关的认知能力、用功能磁共振成像(FMRI)分析执行功能期间的前额叶效率，以及MRI上的额纹状体灰质体积。初步证据表明，COMT的不同细胞效应可能涉及其他基本的分子机制，我们对NRG1诱导的B淋巴母细胞迁移的研究发现，COMT Val/Met基因对迁移和AKT1的磷酸化也有影响(Sei等人，PLOS One，2010)。我们研究了我们的NRG1刺激的B淋巴母细胞系统中AKT1的激活，并研究了COMT和AKT1之间的功能相互作用。对NRG1诱导的AKT1磷酸化的分析显示，与携带MET等位基因的个体相比，COMT Val个体的AKT1磷酸化水平降低。在本研究中，我们发现AKT1的功能编码多态(Rs1130233)和COMT val108/158met基因在AKT1激活的细胞过程中存在显著的交互作用。这些数据表明，AKT1的功能受COMT酶活性的影响，该酶通过S-腺苷蛋氨酸与磷脂酰丝氨酸(PS)的合成竞争，从而调节依赖AKT1的细胞对NRG1介导的信号的反应。由于COMT与其他甲基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。我们正在与其他组织合作，在我们的淋巴细胞中进行有针对性的基因甲基化分析。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.