Barrier structures (e.g. epithelia around tissues, plasma membranes around cells) are required for internal homeostasis and protection from pathogens. Wound detection and healing represent a dormant morphogenetic program that can be rapidly executed to restore barrier integrity and tissue homeostasis. In animals, initial steps include recruitment of leukocytes to the site of injury across distances of hundreds of micrometers within minutes of wounding. The spatial signals that direct this immediate tissue response are unknown. Due to their fast diffusion and versatile biological activities, reactive oxygen species (ROS), including hydrogen peroxide (H2O2), are interesting candidates for wound-to-leukocyte signalling. We probed the role of H2O2 during the early events of wound responses in zebrafish larvae expressing a genetically encoded H2O2 sensor1. This reporter revealed a sustained rise in H2O2 concentration at the wound margin, starting ∼3 min after wounding and peaking at ∼20 min, which extended ∼100−200 μm into the tail fin epithelium as a decreasing concentration gradient. Using pharmacological and genetic inhibition, we show that this gradient is created by Dual oxidase (Duox), and that it is required for rapid recruitment of leukocytes to the wound. This is the first observation of a tissue-scale H2O2 pattern, and the first evidence that H2O2 signals to leukocytes in tissues, in addition to its known antiseptic role.

The neural cell adhesion molecule (NCAM) has been reported to stimulate neuritogenesis either via nonreceptor tyrosine kinases or fibroblast growth factor (FGF) receptor. Here we show that lipid raft association of NCAM is crucial for activation of the nonreceptor tyrosine kinase pathway and induction of neurite outgrowth. Transfection of hippocampal neurons of NCAM-deficient mice revealed that of the three major NCAM isoforms only NCAM140 can act as a homophilic receptor that induces neurite outgrowth. Disruption of NCAM140 raft association either by mutation of NCAM140 palmitoylation sites or by lipid raft destruction attenuates activation of the tyrosine focal adhesion kinase and extracellular signal–regulated kinase 1/2, completely blocking neurite outgrowth. Likewise, NCAM-triggered neurite outgrowth is also completely blocked by a specific FGF receptor inhibitor, indicating that cosignaling via raft-associated kinases and FGF receptor is essential for neuritogenesis.

Ferroptosis is a regulated form of necrotic cell death that is caused by the accumulation of oxidized phospholipids, leading to membrane damage and cell lysis 1 , 2 . While other types of necrotic death such as pyroptosis and necroptosis are mediated by active mechanisms of execution 3 – 6 , ferroptosis is thought to result from the accumulation of unrepaired cell damage 1 . Previous studies suggested that ferroptosis has the ability to spread through cell populations in a wave-like manner, resulting in a distinct spatiotemporal pattern of cell death 7 , 8 . Here we investigate the mechanism of ferroptosis execution and discover that ferroptotic cell rupture is mediated by plasma membrane pores, similarly to cell lysis in pyroptosis and necroptosis 3 , 4 . We further find that intercellular propagation of death occurs following treatment with some ferroptosis-inducing agents, including erastin 2 , 9 and C’ dot nanoparticles 8 , but not upon direct inhibition of the ferroptosis-inhibiting enzyme Glutathione Peroxidase 4 (GPX4) 10 . Propagation of a ferroptosis-inducing signal occurs upstream of cell rupture, and involves the spreading of a cell swelling effect through cell populations in a lipid peroxide- and iron-dependent manner.