Zebrafish pronephros regeneration
The Zebrafish pronephros is a fully functional kidney that maintains water and electrolyte homeostasis during embryogenesis. Similar to the posterior lateral line primordium, a mechano-sensory organ designed to detect fluid flow, it is shaped by a continuous migration of tubular epithelial cells originating at the cloaca, the joint posterior opening of the kidney tubules and the gut. Ablation of single or multiple consecutive cells revealed a robust migratory repair response that instructs cells to adjust their migration pattern to rapidly close the laser-mediated injury. The repair response does not require fluid flow, cilia, or Wnt signaling, but instead depends on the presence of the cancer-associated adhesion molecule EpCAM. Surprisingly, pronephros injuries are not repaired during the first 36 hours post fertilization (36 hpf). We used three different approaches to elucidate the signaling network that orchestrates Zebrafish pronephros repair: first, we compared gene expression profiles of Zebrafish pronephri before and after 36 hpf; second, we performed affinity purification-based mass spectrometry to define the interactome of EpCAM, and third, we performed single-cell next generation sequencing to determine the transcriptome of cells immediately involved in the repair response based on a unique set of candidate genes. These approaches uncovered several novel components of the pronephros repair process triggered by a laser-induced injury. In situ hybridization of candidate genes confirmed their up-regulation in tubular epithelial cells adjacent to the injury, while depletion of some of these genes prevented pronephros repair after injury, suggesting their essential role in the repair process. Knockout of select mammalian homologues in mice delayed the repair response after ischemia/reperfusion injury, suggesting that genes involved in Zebrafish repair responses may provide novel targets to accelerate the repair response after acute kidney injury in humans.