Human non-CpG methylation patterns display both tissue-specific and inter-individual differences suggestive of...

Area of Science:

• Epigenetics
• Genomics

Background:

• DNA methylation (DNAm) is crucial in mammals, primarily studied at CpG sites.
• Non-CpG DNAm is prevalent but less understood regarding its functional relevance, tissue distribution, and individual variability.

Purpose of the Study:

• To investigate non-CpG DNAm across multiple tissues from the same individuals.
• To understand the distribution of non-CpG DNAm in different tissues and individuals.
• To correlate non-CpG DNAm with genomic regulatory features.

Main Methods:

• Methylation sequencing (methyl-seq) of DNA from umbilical cord, cord blood, and peripheral venous blood.
• Hierarchical cluster analysis (HCA) of CpG and non-CpG sites, stratified by cytosine context (CNN).
• Analysis of tissue and inter-individual variation in a second dataset including muscle and cord blood samples.

Main Results:

• Non-CpG methylation clustering patterns differed based on the CNN sequence context.
• CAC methylation sites showed tissue-specific clustering, followed by individual clustering.
• CAT methylation sites predominantly clustered by individual, indicating strong personal influence.

Conclusions:

• CAC DNA methylation exhibits tissue-specific characteristics.
• CAT DNA methylation is significantly influenced by individual factors, potentially genetic or environmental.
• This study highlights the complex, context-dependent nature of non-CpG DNA methylation.