AbstractBackgroundHypertension is a crucial risk factor for developing cardiovascular disease and reducing life expectancy. We aimed to detect DNA methylation (DNAm) variants potentially related to systolic blood pressure (SBP) and diastolic blood pressure (DBP) by conducting epigenome-wide association studies in 60 and 59 Chinese monozygotic twin pairs, respectively.MethodsGenome-wide DNA methylation profiling in whole blood of twins was performed using Reduced Representation Bisulfite Sequencing, yielding 551,447 raw CpGs. Association between DNAm of single CpG and blood pressure was tested by applying generalized estimation equation. Differentially methylated regions (DMRs) were identified bycomb-Papproach. Inference about Causation through Examination of Familial Confounding was utilized to perform the causal inference. Ontology enrichment analysis was performed using Genomic Regions Enrichment of Annotations Tool. Candidate CpGs were quantified using Sequenom MassARRAY platform in a community population. Weighted gene co-expression network analysis (WGCNA) was conducted using gene expression data.ResultsThe median age of twins was 52 years (95% range 40, 66). For SBP, 31 top CpGs (p < 1 × 10–4) and 8 DMRs were identified, with several DMRs withinNFATC1,CADM2,IRX1,COL5A1, andLRAT. For DBP, 43 top CpGs (p < 1 × 10–4) and 12 DMRs were identified, with several DMRs withinWNT3A,CNOT10, andDAB2IP. Important pathways, such as Notch signaling pathway, p53 pathway by glucose deprivation, and Wnt signaling pathway, were significantly enriched for SBP and DBP. Causal inference analysis suggested that DNAm at top CpGs withinNDE1,MYH11,SRRM1P2, andSMPD4influenced SBP, while SBP influenced DNAm at CpGs withinTNK2. DNAm at top CpGs withinWNT3Ainfluenced DBP, while DBP influenced DNAm at CpGs withinGNA14. Three CpGs mapped toWNT3Aand one CpG mapped toCOL5A1were validated in a community population, with a hypermethylated and hypomethylated direction in hypertension cases, respectively. Gene expression analysis by WGCNA further identified some common genes and enrichment terms.ConclusionWe detect many DNAm variants that may be associated with blood pressure in whole blood, particularly the loci withinWNT3AandCOL5A1. Our findings provide new clues to the epigenetic modification underlying hypertension pathogenesis.