SPEG and heart failure: The constitutive Speg‐knockout (KO) mice die in utero or shortly after birth due to heart failure,11 and to overcome the perinatal lethality, we created floxed Speg mice and crossed them with muscle creatine kinase (Mck) cre‐expressing mice, which give rise to striated muscle‐specific Speg‐KO (Speg‐CKO) mice.9