Polycomb repressive complex 2 (Prc2) affects the early development of mouse heart by regulating the trimethylation on lysine 27 of histone H3.[3] In the postnatal heart, embryonic ectoderm development inactivation of the Prc2 core subunit can lead to fatal dilated cardiomyopathy by affecting histone deacetylase activity.[4] Mutations in mixed‐lineage leukemia 2 lead to human Kabuki syndrome, characterized by defects in the atrial and ventricular septa.[5] DOT1 like histone lysine methyltransferase (Dot1l) is a histone methyltransferase that can methylate lysine 79 of histone H3. The gene discussed is DOT1L; the disease is dilated cardiomyopathy.