EP300 and Rubinstein-Taybi syndrome: Mutations in the histone/lysine acetyl transferases (HATs/KATs) CREBBP (CREB-binding protein or CBP; KAT3A; RSTS1, OMIM #180849) and EP300 genes (E1A-binding protein p300; KAT3B; RSTS2, OMIM #613684) represent 60% and 8–10% of clinically diagnosed RSTS cases, respectively3.