Origin and roles of genomic methylation patterns in male germ cells

The epigenetic modification of DNA by methylation at cytosine residues is initiated in the germ line and is required for normal embryonic development in mammals. Marked differences in genomic methylation between male and female gametes arise during gametogenesis and have been implicated in genomic imprinting. While DNA methylation patterns for different types of gene sequences are known to change during spermatogenesis, the precise role(s) of DNA methylation in the normal development of male germ cells is poorly understood. The expression of the one known active form of DNA methyltransferase is highly regulated during spermatogenesis and may provide insight into mechanisms underlying the establishment of methylation patterns in germ cells.