EP300 and Rubinstein-Taybi syndrome due to CREBBP mutations: Pathogenic variants in two highly evolutionarily conserved genes have been implicated in the etiology of RSTS: the CREBBP gene encoding the cAMP response element-binding protein (CREB) binding protein (NM_600140) located in 16p13.3 [12] and the EP300 gene encoding the EA1-associated protein p300 (NM_602700) located in 22q13 [13].