Blood samples as a surrogate of brain methylation

Epigenomic landscapes are variable between cells and tissue types and, fluctuate in time according to a number of factors such as the age related, environmental or nutritional factors among others. Existing biobanks that archive longitudinally assessed and correctly phenotyped samples have not stored exposure-disease relevant target tissue but DNA from peripheral sources such as the whole blood or buccal cells. Thus, a key question for the current epigenetic studies concerns the degree to which easily accessible peripheral tissues (such as blood) can be used to ask questions about the epigenomic changes taking place in inaccessible tissues such as the brain. In the current study we have compared the methylation profiles in brain (cortex and hippocampus) and blood samples within the same individuals in order to create an inventory of epigenetic marks for which measurements in blood are informative for the brain tissue. Bisulphite converted DNA from 13 cortex, hipocamppus and whole blood matched samples and 10 paired peripheral blood mononuclear cells (PBMCs) and whole blood samples were hybridised to the Illumina Infinium 27k Human Methylation Beadchip v1.217