The genetic etiology of RTS, however, has proven heterogeneous with the later identification of RTS-linked mutations in the CBP paralog E1A binding protein p300 (EP300 or p300) located on chromosome 22q13.2 (OMIM 613684, termed RTS type 2, RSTS2) [106]. Here, EP300 is linked to Rubinstein-Taybi syndrome due to EP300 haploinsufficiency.