Notch signaling regulates neuronal versus sensory epithelial fate choice in the zebrafish lateral line system

â—‹Takamasa Mizoguchi1, Satoshi Togawa1, Koichi Kawakami2 and Motoyuki Itoh1

1 Division of Biological Science, Graduate School of Science, Nagoya University
2 Division of Molecular and Developmental Biology, National Institute of Genetics

The lateral line is a simple sensory system of the fish and amphibian that responds to changes in the motion of water. The lateral line system consists of neurons and sensory organs. Both neurons and sensory organs of the posterior lateral line (pLL) system are considered to be derived from pLL preplacodal region. However, how neurons and sensory ephilelia develop separately from the pLL preplacodal region is not clearly understood. The expression analysis of neuroD, which is the early neuronal marker, revealed that posterior lateral line ganglia (pLLG) precursor neurons initially generated in a salt and pepper pattern within the pLL preplacodal region around 10ss. The initial patchy appearance of the pLLG precursors imply that pLLG formation is regulated by Notch-mediated lateral inhibition. We then examined pLLG development in Notch signaling deficient and activated embryos. In Notch-signaling-deficient embryos, pLLG neurons were increased. In contrast, transient Notch activation resulted in a decreased pLLG neurons. To elucidate the fate alternative to neurons regulated by Notch signaling in the pLL development, time-lapse cell fate analysis with photo-activated RFP was performed. We found that labeled pLL preplacodal cells located on vicinity of pLLG neuron at 10ss separated from neurons, migrated to caudal, and formed anterior part of pLLP, which later develops into sensory organs. In accordance with these observation, the number of pLLP cells was decreased in Notch-signaling-deficient embryos. These results suggest that Notch signaling plays an important role in the cell fate choice between neuron and sensory organ in the zebrafish lateral line system.