title: CpG sites associated with NRP1, NRXN2 and miR-29b-2 are hypomethylated in monocytes during ageing.
abstract: BACKGROUND
  Ageing affects many components of the immune system, including innate immune cells like monocytes. They are important in the early response to pathogens and for their role to differentiate into macrophages and dendritic cells. Recent studies have revealed significant age-related changes in genomic DNA methylation in peripheral blood mononuclear cells, however information on epigenetic changes in specific leukocyte subsets is still lacking. Here, we aimed to analyse DNA methylation in purified monocyte populations from young and elderly individuals.
  
  
  RESULTS
  We analysed the methylation changes in monocytes purified from young and elderly individuals using the HumanMethylation450 BeadChip array. Interestingly, we found that among 26 differentially methylated CpG sites, the majority of sites were hypomethylated in elderly individuals. The most hypomethylated CpG sites were located in neuropilin 1 (NRP1; cg24892069) and neurexin 2 (NRXN2; cg27209729) genes, and upstream of miR-29b-2 gene (cg10501210). The age-related hypomethylation of these three sites was confirmed in a separate group of young and elderly individuals.
  
  
  CONCLUSIONS
  We identified significant age-related hypomethylation in human purified monocytes at CpG sites within the regions of NRP1, NRXN2 and miR-29b-2 genes.
authors.affiliation: Molecular Pathology, Institute of Biomedicine and Translational Medicine, University of Tartu, 19 Ravila St, Tartu 50411, Estonia. liina.tserel@ut.ee.
authors.forename: Liina
authors.initials: L
authors.lastname: Tserel
authors.forename: Maia
authors.initials: M
authors.lastname: Limbach
authors.forename: Mario
authors.initials: M
authors.lastname: Saare
authors.forename: Kai
authors.initials: K
authors.lastname: Kisand
authors.forename: Andres
authors.initials: A
authors.lastname: Metspalu
authors.forename: Lili
authors.initials: L
authors.lastname: Milani
authors.forename: Pärt
authors.initials: P
authors.lastname: Peterson