Clinical applicability of methylome sequencing in a pilot study of ischemic stroke individuals

Despite recent progress in screening for genetic causes of cardiovascular disease using genome-wide association studies, identifying causative polymorphisms has not met initial expectations. This has led to interest in exploring the contribution of non-genetic factors in disease etiology. Elevated plasma homocysteine is an independent risk factor for cardiovascular disease but the mechanism for increased risk remains poorly understood. This study evaluates the clinical applicability of screening for genome-wide CpG methylation differences using methyl-CpG binding domain (MBD) protein-enriched genome sequencing (MBD-seq). Peripheral blood genomic DNA methylation in 8 Singaporean-Chinese ischemic stroke patients (4 male, 4 female) was profiled. Differential methylation of genes implicated in hyperhomocysteinemia was observed in males correlating with homocysteine; namely CBS (cystathionine-beta-synthase) and MTHFR (methylenetetrahydrofolate reductase). In females, hypomethylation of the LDLR (low density lipoprotein receptor) and CELSR1 (cadherin, EGF LAG seven-pass G-type receptor 1) genes were observed in the hypertensive group (2 normal and 2 hypertensive individuals). While the number of clinical samples analysed is small, the findings of this evaluation suggest that MBD-seq is a suitable and sufficiently sensitive technology to determine methylation variability. The results presented warrant an expanded case-control study to determine the pathophysiological implications of DNA methylation for hyper-homocysteinemia.