title: DNA cytosine hydroxymethylation levels are distinct among non-overlapping classes of peripheral blood leukocytes.
abstract: Peripheral blood leukocytes are the most commonly used surrogates to study epigenome-induced risk and epigenomic response to disease-related stress. We considered the hypothesis that the various classes of peripheral leukocytes differentially regulate the synthesis of 5-methylcytosine (5mCG) and its removal via Ten-Eleven Translocation (TET) dioxygenase catalyzed hydroxymethylation to 5-hydroxymethylcytosine (5hmCG), reflecting their responsiveness to environment. Although it is known that reductions in TET1 and/or TET2 activity lead to the over-proliferation of various leukocyte precursors in bone marrow and in development of chronic myelomonocytic leukemia and myeloproliferative neoplasms, the role of 5mCG hydroxymethylation in peripheral blood is less well studied.
  
  
  
  We developed simplified protocols to rapidly and reiteratively isolate non-overlapping leukocyte populations from a single small sample of fresh or frozen whole blood. Among peripheral leukocyte types we found extreme variation in the levels of transcripts encoding proteins involved in cytosine methylation (DNMT1, 3A, 3B), the turnover of 5mC by demethylation (TET1, 2, 3), and DNA repair (GADD45A, B, G) and in the global and gene-region-specific levels of DNA 5hmCG (CD4+ T cells≫CD14+ monocytes>CD16+ neutrophils>CD19+ B cells>CD56+ NK cells>Siglec8+ eosinophils>CD8+ T cells).
  
  
  
  Our data taken together suggest a potential hierarchy of responsiveness among classes of leukocytes with CD4+, CD8+ T cells and CD14+ monocytes being the most distinctly poised for a rapid methylome response to physiological stress and disease.
authors.affiliation: Department of Foods and Nutrition, University of Georgia, Athens, GA, USA. Electronic address: nhohos@uga.edu.
authors.forename: Natalie M
authors.initials: NM
authors.lastname: Hohos
authors.affiliation: Department of Genetics, University of Georgia, Athens, GA, USA. Electronic address: klee84@uga.edu.
authors.forename: Kevin
authors.initials: K
authors.lastname: Lee
authors.affiliation: Institute of Bioinformatics, University of Georgia, Athens, GA, USA. Electronic address: lxji@uga.edu.
authors.forename: Lexiang
authors.initials: L
authors.lastname: Ji
authors.affiliation: Department of Chemistry, Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, Howard Hughes Medical Institute, The University of Chicago, Chicago, IL, USA. Electronic address: miaoyu1988@uchicago.edu.
authors.forename: Miao
authors.initials: M
authors.lastname: Yu
authors.affiliation: Department of Genetics, University of Georgia, Athens, GA, USA. Electronic address: kandu@uga.edu.
authors.forename: Muthugapatti M
authors.initials: MM
authors.lastname: Kandasamy
authors.affiliation: Clinical and Administrative Pharmacy, University of Georgia, Athens, GA, USA. Electronic address: bgp@uga.edu.
authors.forename: Bradley G
authors.initials: BG
authors.lastname: Phillips
authors.affiliation: Department of Foods and Nutrition, University of Georgia, Athens, GA, USA.
authors.forename: Clifton A
authors.initials: CA
authors.lastname: Baile
authors.affiliation: Department of Chemistry, Department of Biochemistry and Molecular Biology, Institute for Biophysical Dynamics, Howard Hughes Medical Institute, The University of Chicago, Chicago, IL, USA. Electronic address: chuanhe@uchicago.edu.
authors.forename: Chuan
authors.initials: C
authors.lastname: He
authors.affiliation: Department of Genetics, University of Georgia, Athens, GA, USA. Electronic address: schmitz@uga.edu.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Schmitz
authors.affiliation: Department of Genetics, University of Georgia, Athens, GA, USA. Electronic address: meagher@uga.edu.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Meagher
mesh_terms: D044503:5-Methylcytosine / Q000031:analogs & derivatives* / Q000378:metabolism*; D001402:B-Lymphocytes / Q000166:cytology; D002469:Cell Separation / Q000379:methods*; D019175:DNA Methylation; D004260:DNA Repair / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D044127:Epigenesis, Genetic; D006801:Humans; D013601:T-Lymphocytes / Q000166:cytology
chemical_list: D004268:DNA-Binding Proteins; C011865:5-hydroxymethylcytosine; D044503:5-Methylcytosine
keywords: 5-Hydroxymethylcytosine; Cellular memory; Disease; Epigenetic control; Epigenome-induced risk; Surrogate cells