Researchers at the European Molecular Biology Laboratory [EMBL] in Heidelberg have now discovered how one of these signaling pathways controls the life and death of cells in the fruit fly. The study will be published in this week's issue of the journal Cell.
The breakthrough came as Barry Thompson from Stephen Cohen's group at EMBL looked at a recently discovered signaling pathway called Hippo.
"Hippo acts as a switch between cell division and death," says Barry Thompson, "if the pathway is too active, tissues overgrow because too many cells divide and too few die. But until now, we hadn't found a connection between the signals and the cellular machinery that drives growth."
Using sophisticated genetic techniques, Thompson and Cohen established that a small molecule, a microRNA called bantam, makes this link. Without bantam, tissues grow too slowly and remain smaller than normal. The amount of bantam produced by the cell directly depends on the amount of traffic on the Hippo signaling pathway, and higher levels of bantam prompt more cell division.
The next step will be to identify the RNAs that bantam docks onto to control. This will provide a more complete view of the Hippo pathway and may provide insights into the central role it plays in tissue growth and cancers in humans and other organisms.