In others, such as Alagille syndrome (deletion of 20p12; OMIM 118450) or Rubinstein-Taybi syndrome (deletion of 16p13.3; OMIM 180849), haploinsufficiencies of a single gene (Jagged1 (JAG1) or CREBBP, respectively) accounts for all the characteristic features [30], [31], [32]. This evidence concerns the gene JAG1 and Alagille syndrome.