The role of CBP and p300 during the development was first revealed by the observations that human CBP gene was disrupted in a dominant genetic disorder, Rubinstein-Taybi Syndrome (RTS), which was characterized by craniofacial and limb defects, mental retardation as well as developmental anomalies of the eye, heart, kidney, lung, skin and testes [15]. This evidence concerns the gene CREBBP and Rubinstein-Taybi syndrome.