Consider the relationship between an air traffic controller and a pilot. The pilot gets the passengers to their destination, but the air traffic controller decides when the plane can take off and when it must wait. The same relationship plays out at the cellular level in animals, including humans. A region of an animal’s genome – the controller – directs when a particular gene – the pilot – can perform its prescribed function.
These are images of mouse embryonic stem cells which grow in a round colony of cells (A) and express Sox2 (B), shown in red. Sox2 control region-deleted cells have lost the typical appearance of embryonic stem cells (C) and do not express Sox2 (D). The DNA is shown in blue in B and D.
Credit: Jennifer Mitchell/University of Toronto