On the contrary, binding of ActA to the R206H mutant receptor activates the downstream signaling through canonical SMAD1/5/8 mediators in several cell types expressing mutated cDNA, in induced pluripotent stem cells (iPSC) derived from FOP patients and in vivo, in mice models [8,9,36]. Here, SMAD1 is linked to fibrodysplasia ossificans progressiva.