The Opto-inflammasome in zebrafish: a tool to study cell and tissue responses to speck formation and cell death

The inflammasome is a conserved system for the intracellular detection of danger or pathogen signals. By forming a large intracellular multiprotein signaling platform, it activates downstream effectors that initiate a rapid necrotic programmed cell death (PCD) termed pyroptosis and activation and secretion of pro-inflammatory cytokines to warn and activate surrounding cells. However, inflammasome activation is difficult to control on a single-cell level using canonical triggers. We constructed Opto-Asc, a light-responsive form of the inflammasome adaptor protein ASC (Apoptosis-Associated Speck-Like Protein Containing a CARD) which allows tight control of inflammasome formationin vivo.

We introduced a cassette of this construct under the control of a heat shock element into zebrafish in which we can now induce Asc inflammasome (speck) formation in single cells of the skin.

We find that cell death resulting from Asc speck formation is morphological distinct from apoptosis in periderm but not in basal cells. Asc induced PCD in can lead to apical or basal extrusion from the periderm. The apical extrusion in periderm cells depends on Caspb but and triggers a strong Ca²⁺signaling response in nearby cells.