Figure 2. Myocardial changes after cardiac injury in larval and adult zebrafish.

Larval (a-e) and adult (a′-e′) zebrafish hearts consist of a single ventricular (red) and atrial (green) chamber. After injury (b, b′) pre-existing mature cardiomyocytes de-differentiate, re-activate earlier cardiac transcription factors (red nuclei) (c, c′) and proliferate (d, d′) to contribute new cardiomyocytes to the injured area (e,e′). In larvae atrial cardiomyocytes also respond to injury by dedifferentiating, migrating and then transdifferentiating to a ventricular fate (Yellow cells, c-e). De-differentiation involves the disassembly of sacromeres and cell-cell contacts (inset).

V: Ventricle, A: Atrium, Blue and red nuclei: differentiated and de-differentiated nuclei, respectively.