Researchers crack DNA reprogramming mechanism
Saarbruecken – For a decade, stem cell researchers have tried to unravel how epigentic reprogramming works at the molecular level. Now, German researchers have discovered how the epigenetic code in the paternal part of the genome of a zygote is reset, and how the maternal genome conserves epigenetic marks on its DNA. A team under Jörn Walter from the University of Saarbrücken found that 5’ methyl cytosine marks on the paternal genome, which block transcription, disappeared in male pronuclei of the zygote, while a new modification termed 5’ hydroxymethl cytosine occurred. The transformation is catalysed by the tet3 enzyme in the paternal pronucleus, and erasure of the epigenetic memory is prevented in the maternal genome by another enzyme called PGC7. The discovery of the enzymes responsible for resetting a genome is good news for stem cell researchers who try to coax stem cells to differentiate into particular cells in the human body. It opens up targeted activation of genes that drive development in selected cell lines.