DNA Methylation Polymorphisms Precede Any Histological Sign of Atherosclerosis in Mice Lacking Apolipoprotein E

The present work investigates the occurrence and significance of aberrant DNA methylation patterns during early stages of atherosclerosis. To this end, we asked whether the genetically atherosclerosis-prone APOE-null mice show any changes in DNA methylation patterns before the appearance of histologically detectable vascular lesion. We exploited a combination of various techniques: DNA fingerprinting, in vitro methyl-accepting assay, 5-methylcytosine quantitation, histone post-translational modification analysis, Southern blotting, and PCR. Our results show that alterations in DNA methylation profiles, including both hyper- and hypomethylation, were present in aortas and PBMC of 4-week-old mutant mice with no detectable atherosclerotic lesion. Sequencing and expression analysis of 60 leukocytic polymorphisms revealed that epigenetic changes involve transcribed genic sequences, as well as repeated interspersed elements. Furthermore, we showed for the first time that atherogenic lipoproteins promote global DNA hypermethylation in a human monocyte cell line. Taken together, our results unequivocally show that alterations in DNA methylation profiles are early markers of atherosclerosis in a mouse model and may play a causative role in atherogenesis. The present work investigates the occurrence and significance of aberrant DNA methylation patterns during early stages of atherosclerosis. To this end, we asked whether the genetically atherosclerosis-prone APOE-null mice show any changes in DNA methylation patterns before the appearance of histologically detectable vascular lesion. We exploited a combination of various techniques: DNA fingerprinting, in vitro methyl-accepting assay, 5-methylcytosine quantitation, histone post-translational modification analysis, Southern blotting, and PCR. Our results show that alterations in DNA methylation profiles, including both hyper- and hypomethylation, were present in aortas and PBMC of 4-week-old mutant mice with no detectable atherosclerotic lesion. Sequencing and expression analysis of 60 leukocytic polymorphisms revealed that epigenetic changes involve transcribed genic sequences, as well as repeated interspersed elements. Furthermore, we showed for the first time that atherogenic lipoproteins promote global DNA hypermethylation in a human monocyte cell line. Taken together, our results unequivocally show that alterations in DNA methylation profiles are early markers of atherosclerosis in a mouse model and may play a causative role in atherogenesis. Atherosclerosis and its complications are a major cause of death and disability in the developed world. The disease is characterized by infiltration of lipid particles in the arterial wall, accompanied by the recruitment of inflammatory and immune cells, migration and proliferation of smooth muscle cells (SMC), 1The abbreviations used are: SMC, smooth muscle cells; mC, 5-methylcytosine; CG, CpG dinucleotide; DMP, DNA methylation polymorphism; HPCE, high performance capillary electrophoresis; MSAP, methylation-sensitive amplified polymorphism; SAM, S-adenosyl methionine; PBMC, peripheral blood mononuclear cell; WDMP, wild type DNA methylation polymorphism; MDMP, mutant DNA methylation polymorphism; UK, United Kingdom; EST, expressed sequence tag; WT, wild type; LDL, low density lipoprotein; VLDL, very low density lipoprotein; HDL, high density lipoprotein; HL, high VLDL + LDL mixture; WL, low VLDL + LDL mixture. and synthesis of extracellular matrix. These processes eventually result in the gradual development of an elevated lipid-rich, fibrocellular lesion (1Ross R. N. Engl. J. 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