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Fig. 9
Mechanistic models for lateral line regeneration. (A) Under normal conditions, the pLLn (thick dark green thread) nrg1-III-activated erbb2/3 receptors within Schwann cells (SWCs, light green) keep interneuromast cells (INCs, bright green) quiescent by limiting the Wnt activity. Upon the loss of distal neuromasts by tail amputation, the lateral line nerve is weakened (thin light green thread) in the proximity of the cutting edge to break the quiescence of INCs (red outlines). The Wnt activity in INCs is elevated and results in cluster formation. (B) Upon specific ablation of neuromasts by NTR-hKikGR protein (bright green spots)-induced by Mtz without damaging surrounding posterior lateral line nerve and SWCs, INCs remain quiescent by integral EGF inhibition. Most macrophages crawl onto INCs, filling the gap without successful neuromast regeneration. However, occasionally macrophages could infiltrate in between INCs and SWCs. It breaks the contact between INCs and SWCs and the inhibition of EGF signaling. INCs are then activated to be able to differentiate and regenerate new neuromasts through cluster formation.