Your mother always told you never to compare yourself with others, but in the methylation game, comparisons can reveal lots of cool info. Researchers now report that by comparing the methylomes of eight species, they found out that the placement of the H3K36me3 mark in Drosophila actually predicts where DNA methylation happens in other invertebrates.
The U.K.-based researchers compared gene-body methylation patterns of eight species: sea anemone, sea squirt, honey bee, silk moth, rice, Arabidopsis, puffer fish, and humans. (In invertebrates, itâs the gene bodies that are typically methylated, not promoters or other regions.) Most of the invertebrates had two types of genesâlow-CpG genes and high-CpG genesâwhereas humans and plants had just one type. Here are a few other things they found:
- Gene-body methylation is mostly limited to low-CpG somatic and germline genes in invertebrates.
- Gene-body methylation is strongly inversely correlated with CpG content (low-CpG genes are highly methylated, for example), but doesnât seem to correlate with expression levels in invertebrates.
- Invertebrate genomes have conserved peaks of methylation within exons.
- Interestingly, those genes that were CpG poor in invertebrates are orthologs of Drosophila genes that have lots of H3K36me3, which are genes involved in basic biological processes.
These findings led the team to propose that âhistone modifications could, indirectly, affect sequence change over evolutionary time,â say the researchers.
Do your own methylome comparisons at Genome Research, September 2011.