DNA methylation during early mammalian development

Abstract

DNA methylation – a DNA modification taking place predominately at CpG dinucleotides –shows a very dynamic behavior during early mammalian embryonic development. Soon after fertilization the parental genomes undergo demethylation with only a few methylated sequences escaping it, for example imprints. Later in development a methylation wave will establish new methylation marks to the forming embryo, important for its survival. In addition, sequences which escape demethylation at the first place, will eventually become demethylated in the forming Primordial Germ Cells (PGCs), so that new sex – specific epigenetic marks will be established during gametogenesis. DNA methylation, together with other modifications like histone modifications, are of a crucial importance during embryonic development and stem cell differentiation, since aberrant methylation patterns are linked with lethality, diseases and cancer. 5