Abstract
Aberrant histone lysine methylation patterns that change chromatin structure can promote dysregulated gene transcription and disease progression. Diabetic conditions such as high glucose (HG) are known to alter key pathologic pathways. However, their impact on cellular histone lysine methylation is unknown. We hypothesized that chronic HG can induce aberrant changes in histone H3 lysine 4 and lysine 9 dimethylation (H3K4me2 and H3K9me2) within target cells. Chromatin immunoprecipitation linked to microarrays (ChIP-on-chip) is currently a widely used approach for acquiring genome-wide information on histone modifications. We adopted this approach to profile and compare the variations in H3K4me2 and H3K9me2 in human gene coding and CpG island regions in THP-1 monocytes cultured in normal glucose and HG. Subsequently, we identified key relevant candidate genes displaying differential changes in H3K4me2 and H3K9me2 in HG versus normal glucose and also validated them with follow-up conventional ChIPs. Relevance to human diabetes was demonstrated by noting that H3K9me2 at the coding and promoter regions of two candidate genes was significantly greater in blood monocytes of diabetic patients relative to normal controls similar to the THP-1 data. In addition, regular mRNA profiling with cDNA arrays revealed correlations between mRNA and H3K9me2 levels. These novel results show histone methylation variations, for the first time, under diabetic conditions at a genome-wide level.
Highlights
Tribute to epigenetic heritable changes in gene function that do not involve a local change in DNA sequence
Chromatin immunoprecipitation combined with DNA array analysis (ChIP-on-chip)2 is the best approach for profiling and acquiring genome-wide information on histone modifications
To examine whether histone methylation is altered by diabetic conditions, in this paper, we used the Chromatin Precipitation (ChIP)-on-chip approach to analyze histone lysine methylation variations caused by high glucose (HG) in THP-1 cells
Summary
Tribute to epigenetic heritable changes in gene function that do not involve a local change in DNA sequence. Chromatin immunoprecipitation combined with DNA array analysis (ChIP-on-chip) is the best approach for profiling and acquiring genome-wide information on histone modifications. We recently reported that HG treatment of human monocytes leads to dynamic changes in histone H3 lysine acetylation [26] It is not clear whether methylation undergoes such variations. We examined how HG affects the status of chromatin histone lysine methylation genome-wide by profiling histone H3 lysine 4 dimethylation (H3K4me2) and lysine 9 dimethylation (H3K9me2) in THP-1 monocytes cultured in NG and HG. We tested the in vivo relevance of the THP-1 data by examining whether key target genes were methylated at the coding or promoter regions in peripheral blood monocytes obtained from diabetic patients. Our new results could provide key links between these susceptible genes and the diabetic state, and uncover a potential mechanistic basis for metabolic memory, diabetes, and its complications
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