In “Stem Cell Suicide Switch: Human embryonic stem cells swiftly kill themselves in response to DNA damage.” (The Scientist, May 3, 2012), Megan Scudellari reports
Human embryonic stem cells give a whole new meaning to the phrase “taking one for the team.” Unlike any other known human cell type, hESCs are primed to immediately throw themselves on the sword if they experience any DNA damage, according to research published online today (May 3) in Molecular Cell.
One reason why we are all here.
Apoptosis is traditionally a lengthy process that involves the activation of a protein called Bax, which travels to the mitochondria and initiates the release of caspases, or “executioner” proteins that cause cell death. To investigate how hESCs initiate the process so rapidly, the researchers tagged Bax with an antibody that lights up when the protein is active. They were surprised to find that Bax is already active in healthy hESCs, unlike every other cell type in which Bax is activated only when a cell is damaged or dying. “I was stunned,” said Deshmukh. “I thought something was wrong. We spent a lot of time convincing ourselves that these cells were healthy and not actively dying.”
The team also saw that active Bax was not located in the mitochondria but in the Golgi, a packaging organelle. It is possible that cells sequester active Bax there, like a gun locked in a case, to prevent it from accidentally triggering cell death. “The cells’ activated it and tethered it to a place where it is not causing immediate damage,” said Deshmukh. That way, Bax is ready to go at a moment’s notice.
Which is completely consistent with random evolution, right?