Life often modifies its genetic material without changing the letters of the genetic code. One of the main ways this is done is through the addition of a chemical unit called a methyl group to a gene. Joseph Ecker of the Salk Institute in La Jolla, California and colleagues have used a new method to sequence the complete “methylome” of the cress Arabidopsis for every letter of its genetic code, giving a far more detailed recipe than prior efforts. So just sequencing the DNA genome is not enough, you have to know what DNA is active and has been de-activated by a methyl group.
The Arabidopsis genome comprises some 120 million DNA bases (3% of the size of the human genome) – so the team has developed open-source software to “browse” the genome and find where methylation is controlling gene expression. The program will be able to track more epigenetic data as it is produced, forming a global resource for collecting and analysing it.
They have already begun using these methods for sequencing of the human methylome.”
Ecker says that the team will look into how methylation affects the development of human stem cells as they change into other types of cells.
Silencing the expression of DNA methyltransferase Dnmt3, a key driver of epigenetic global reprogramming, in newly hatched larvae led to a royal jelly–like effect on the larval developmental trajectory; the majority of Dnmt3 small interfering RNA–treated individuals emerged as queens with fully developed ovaries. Our results suggest that DNA methylation in Apis is used for storing epigenetic information, that the use of that information can be differentially altered by nutritional input, and that the flexibility of epigenetic modifications underpins, profound shifts in developmental fates, with massive implications for reproductive and behavioral status.