MSTN and hydrops fetalis: Theactivation of the myostatin precursor complex promotes myostatin binding toactivin receptor type IIB (ActRIIB) on myofibrils, and downstream mediators causedecapentaplegic homolog 2 (SMAD2) and decapentaplegic homolog 3 (SMAD3)phosphorylation and also affect the corresponding gene transcription [58].Elevated levels of myostatin have also been observed in HF.