In toto live imaging of Erk signaling dynamics in developing zebrafish hepatocytes

Regional and tissue-wide regulation of signaling pathways orchestrates cellular proliferation and differentiation during organ development. In this study, we established an imaging platform for longitudinal analysis of liver development in live developing zebrafish. We generated hepatocyte-specific transgenic lines for kinase translocation reporters of extracellular signal-regulated kinase (Erk) and c-Jun N-terminal kinase (Jnk) signaling, and with these we captured signaling dynamics that govern rapid expansion of hepatocytes toward creation of the functioning liver at single-cell resolution. Our findings reveal Erk signaling fluctuations as the liver develops and introduce methodology for investigating cell-type specific signaling dynamics during organ morphogenesis.