“Bring out yer dead!” Thankfully, epithelial sheets have a much more efficient and beautiful way of clearing out dying cells than the famous Monty Python scene. Today’s stunning images are from a paper describing the signaling epithelial cells use to push out dying cells. It’s no wonder that the authors’ image made the cover of Journal of Cell Biology!
The function and health of an organ strongly depends on the integrity of the epithelial sheet protecting it. In order to preserve the epithelial barrier, dying cells are pushed out of the epithelial sheet in a precise and finely-tuned process called apoptotic cell extrusion. In this event, cells surrounding the dying, apoptotic cell form an actin and myosin ring that contracts to push the dying cell out of the sheet. A recent paper describes the signaling that takes place to initiate cell extrusion. The dying cell produces a signal called bioactive lipid sphingosine-1-phosphate (S1P), which activates actin-myosin contraction via its receptor (S1P2) in neighboring cells. The images above show epithelial sheets in normal and S1P2 mutant zebrafish larvae. In the mutant, the apoptotic cell (green) stays in the epithelial sheet and lacks the actin ring (red) seen in the wild-type tissue.
Gu, Y., Forostyan, T., Sabbadini, R., & Rosenblatt, J. (2011). Epithelial cell extrusion requires the sphingosine-1-phosphate receptor 2 pathway originally published in The Journal of Cell Biology, 193 (4), 667-676 DOI: 10.1083/jcb.201010075