Fig. 5

Regeneration occurs through transdifferentiation. (A–C) Lineage-labeled embryo at 48 hpf, just before laser ablation, showing brn3c:gfp-labeled hair cells in the utricular macula (A), two clusters (c1 and c2) of lineage-labeled cells (B) and an overlay showing both labels (C). Most lineage-labeled cells are support cells. Asterisks mark hair cells that were subsequently targeted for ablation. (D–F) The same specimen 3 h post-ablation. A notable gap in the hair cell layer (arrow) marks the position previously occupied by one of the targeted hair cells. Accumulation of lineage label plus GFP beneath the macula appears to show a fragmenting apoptotic hair cell being ejected from the macula (arrowhead). Labeled support cells are still evident in clusters c1 and c2. (G–I) The same specimen 17 h post-ablation. Support cells in cluster c1 are still evident, though fluorescence intensity has decreased as described in Materials and methods. In contrast, lineage label is no longer visible in the support cell layer in cluster c2. Instead, lineage-labeled cells now occupy the hair cell layer and express brn3c:gfp. Much of the lineage label is concentrated in vesicles, as is typical at this stage following laser irradiation (see Materials and methods). All images show lateral views with anterior to the left and dorsal to the top.