As an embryo1 develops, different genes3 are turned on in different cells, to form muscles, neurons and other bodily parts. Inside each cell's nucleus4, genetic5 sequences known as enhancers act like remote controls, switching genes on and off. Scientists at the European Molecular6 Biology Laboratory (EMBL) in Heidelberg, Germany, can now see -- and predict -- exactly when each remote control is itself activated7, in a real embryo. Their work was recently published in Nature Genetics.
Stefan Bonn, Robert Zinzen and Charles Girardot, all in Eileen Furlong's lab at EMBL, found that specific combinations of chromatin(核染色质) modifications8 -- chemical tags that promote or hinder(阻碍,打扰) gene2 expression -- are placed at and removed from enhancers at precise times during development, switching those remote controls on or off.
"Our new method provides cell-type specific information on the activity status of an enhancer and of a gene, within a developing multicellular embryo," says Furlong.
The scientists looked at known enhancers, and compared those that were active to those that were inactive in a type of cells called mesoderm(中胚层) at a particular time in fruit fly development. They noted9 what chromatin modifications each of those enhancers had, and trained a computer model to accurately10 predict if an enhancer is active or inactive, based solely11 on what chromatin marks it bears.
In future, the scientists plan to use this method to study the interplay between the activity status of an enhancer and the presence of key switches, termed transcription factors, at different stages of embryonic12 development, and in different tissue types, generating an ever more complete picture of how a single cell grows into a complex organism.