van Eijk Kristel R, de Jong Simone, Strengman Eric, Buizer-Voskamp Jacobine E, Kahn René S, Boks Marco P, Horvath Steve, Ophoff Roel A
Department of Psychiatry, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
UCLA Center for Neurobehavioral Genetics, Semel Institute for Neuroscience and Human Behavior, University of California Los Angeles (UCLA), Los Angeles, CA, USA.
Eur J Hum Genet. 2015 Aug;23(8):1106-10. doi: 10.1038/ejhg.2014.245. Epub 2014 Nov 26.
Emerging evidence suggests that schizophrenia (SZ) susceptibility involves variation at genetic, epigenetic and transcriptome levels. We describe an integrated approach that leverages DNA methylation and gene expression data to prioritize genetic variation involved in disease. DNA methylation levels were obtained from whole blood of 260 SZ patients and 250 unaffected controls of which a subset with gene expression data was available. By assessing DNA methylation and gene expression in cases and controls, we identified 432 CpG sites with differential methylation levels that are associated with differential gene expression. We hypothesized that genetic factors involved in these methylation levels may be associated with the genetic risk of SZ susceptibility. To test this hypothesis, we used results from the Psychiatric Genomics Consortium SZ genome-wide association study (GWAS). We observe an enrichment of SZ-associated SNPs in the mQTLs of which the associated CpG site is also correlated with differential gene expression in SZ. While this enrichment was already apparent when using nominal significant thresholds, enrichment was even more pronounced when applying more stringent significance levels. One locus, previously identified as susceptibility locus in a SZ GWAS, involves SNP rs11191514:C>T, which regulates DNA methylation of calcium homeostasis modulator 1 that is also associated with differential gene expression in patients. Overall, our results suggest that epigenetic variation plays an important role in SZ susceptibility and that the integration of analyses of genetic, epigenetic and gene expression profiles may be a biologically meaningful approach for identifying disease susceptibility loci, even when using whole blood data in studies of brain-related disorders.
新出现的证据表明,精神分裂症(SZ)易感性涉及基因、表观遗传和转录组水平的变异。我们描述了一种综合方法,该方法利用DNA甲基化和基因表达数据来确定与疾病相关的基因变异的优先级。DNA甲基化水平来自260名SZ患者和250名未受影响对照的全血,其中有一部分可获得基因表达数据。通过评估病例组和对照组中的DNA甲基化和基因表达,我们确定了432个甲基化水平存在差异的CpG位点,这些位点与基因表达差异相关。我们假设参与这些甲基化水平的遗传因素可能与SZ易感性的遗传风险相关。为了验证这一假设,我们使用了精神基因组学联盟SZ全基因组关联研究(GWAS)的结果。我们观察到在甲基化数量性状位点(mQTL)中与SZ相关的单核苷酸多态性(SNP)富集,其中相关的CpG位点也与SZ中的基因表达差异相关。虽然在使用名义显著性阈值时这种富集已经很明显,但在应用更严格的显著性水平时,富集更为显著。一个位点,先前在SZ的GWAS中被确定为易感位点,涉及SNP rs11191514:C>T,它调节钙稳态调节剂1的DNA甲基化,而钙稳态调节剂1也与患者的基因表达差异相关。总体而言,我们的结果表明表观遗传变异在SZ易感性中起重要作用,并且即使在脑相关疾病研究中使用全血数据,整合遗传、表观遗传和基因表达谱分析可能是识别疾病易感位点的一种具有生物学意义的方法。