ABSTRACT
Epigenetics refers to heritable changes in gene expression that occur without modifications at the DNA sequence level. Changes are regulated by DNA methylation at the 5-carbon of cytosine (5-methylcytosine [5mC]), posttranslational modifications in the N-terminal amino acids of histones, and the presence of noncoding RNAs. DNA methylation occurs at cytosine residues that are followed by a guanine (CpG dinucleotide). DNA methylation is an epigenetic mechanism involved in the regulation of many biological processes including cell-specific gene expression, genomic imprinting, and genomic stability. There are three periods of global resetting of DNA methylation during a man's life. The first occurs in the preimplantation embryo, the second in primordial germ cells (PGCs), and the third at spermatogenesis. The demethylation of maternal and paternal genomes during early embryonic development is asynchronous. There are different approaches to analyze DNA methylation. Sperm DNA isolation could be performed using the 'classical' phenol/chloroform extraction or by commercially available kits.
