Figure 4.

Cardiac proliferation and regenerative pathways are under the control of RA signaling. Schematic of aldh1a2 expression in an apical resection model of adult zebrafish; however, a similar response is seen from other injuries and albeit subdued, in murine models [177]. In response to injury, enhanced aldh1a2 expression is observed throughout the epicardium (A) and in the endocardium of both cardiac chambers (B). In the epicardium, aldh1a2 expression becomes restricted to the site of injury, concomitant with deposition of the first layers of new muscle which require the coordination of RA-driven myocardial and epicardial events. Proper regeneration of the adult zebrafish heart requires RA synthesis from the endocardium as well, where RA synthesis rapidly becomes restricted to the site of injury as early as 24 h post-amputation. Dpa: day post-amputation, OFT: outflow tract.