Genomic imprinting

Abstract

It is increasingly well accepted not only in geneticists and biologists but also in physicians that maternal and paternal chromosomes in mammals can function differently.This heritable, sex-specific difference in gene expression is thought to be brought about by marking genes during gamatogenesis and has been termed genomic imprinting. More than 10 imprinted genes have been identified so far in mice or humans.They have shown their own characteristic patterns of gene expression which provide important clues to understand the molecular mechanism of imprinting. DNA methylation has been regarded as a promising candidate for the primary mark of imprinted genes. DNA methyltransferase knockout mice have demonstrated that DNA methylation plays a critical role in genomic imprinting. While regions with gamate-specific differential methylation have been identified in the U19 and Igf2r genes and a targeted deletion of the H19 gene demonstrated the predicted disruption of Igf2 imprinting, the molecular mechanism of genomic imprinting is still largely unknown and is a challenging issue.