Whole-Body HOListic Imaging in Larval Zebrafish Maps Cross-Organ Cell Communication

HHMI Janelia's HOListic system performs whole-body in vivo functional imaging in larval zebrafish ubiquitously expressing GCaMP, extracting roughly 400 activity clusters that map largely to single organs and often to subcompartments. Applying it revealed unreported cold sensitivity in chondrocytes, a hindbrain-gut topographic mapping confirmed by optogenetics, and a possible brain control mechanism in which hypoxia shifts blood flow away from viscera and brain inhibition restores flow within seconds. The work argues that broad measurement across context can find control nodes that the classic perturb-and-draw-arrows approach misses.