MFN2 and hydrops fetalis: To test our hypothesis, we treated myocytes from HF hearts and corresponding age-matched control hearts with cell-permeable peptides that can either destabilize the fusion-constrained conformation of mitofusin 2 (TAT-MP2Gly) or promote the fusion-permissive conformation (1 μM TAT-MP1Gly) (Franco et al., 2016).