This confirms that ligands which activate MyD88-dependent signaling pathways can enhance aberrant ActA/Alk2R206H-induced pSmad1/5 in a manner similar to that reported for BMP-induced signaling in Alk2wt cells [27,28,29,30] and cells from FOP patients [31]. Here, ACTA1 is linked to fibrodysplasia ossificans progressiva.