Genome-wide identification of new imprinted genes

In the mid-1980s, elegant studies on mouse embryos revealed that both parental genomes are required for normal development leading to the discovery of genomic imprinting. Imprinting is a parent-of-origin-dependent epigenetic mechanism whereby a subset of autosomal genes is expressed from only one of the parental alleles. Imprinting control involves both DNA- and histone-methylation, which differentially mark the parental alleles. More than a hundred imprinted genes have been identified so far, many of which play important roles in the regulation of growth and development. Nonetheless, the full extent of imprinting and its biological functions remain underestimated. In this review, we describe recently developed strategies to identify novel imprinted genes and highlight the potential of combining several high throughput approaches. By integrating databases obtained from epigenome- and transcriptome-wide analyses, we now have the unique opportunity to identify all the imprinted genes in the human/mouse genomes.