Among the Hh ligand genes expressed in the zebrafish heart, Shha is the ligand most strongly upregulated during regeneration (Wang J, et al. Nature 2015) (Figure 5B). Therefore, we focused on Shha as the major Hh ligand in heart regeneration. Future studies employing conditional and combinatorial inhibition of Hh ligands will be necessary to definitively determine the relative contribution of each ligand.