Ever notice how it gets more interesting when there’s more than just black or white, love or hate, good or evil? The real action seems to take place in the gray areas. It seems true for methylated alleles as well. A recent paper looking into genomic imprinting found new evidence that both genomic and environmental effects on gene function share a common pathway.
Researchers led by King’s College London’s Jonathan Mill set out to find novel examples of genomic imprinting. They embarked on what they assume is the first quantitative genomic survey of allele-specific DNA methylation (ASM), using microarrays to query human DNA digested with methylation-sensitive restriction enzymes, followed up by other methods including bisulfite sequencing.
Their data suggest that the genome contains more than 35,000 ASM-associated sites. Yet only about 10% of these are likely to be of parental origin or trans-acting, with the remaining 90% or so being cis-acting. This “goes against the traditional textbook definition of epigenetics as something that occurs independently of DNA sequence,” Mill remarked.
More surprising still is the fact that in many cases the ASM doesn’t seem to be completely biphasic – that is, they observed more inter-subject and inter-tissue variation of which allele was methylated, and by how much, than if the effect was absolute.
Read more about why you’ll be thinking about ASM everytime you see a genome-wide association study; The American Journal of Human Genetics, February 2010