[From gene to disease: arteriohepatic dysplasia or Alagille syndrome]

Alagille syndrome (AGS), also known as arteriohepatic dysplasia, is an autosomal dominant disorder with a prevalence of approximately one in 70,000 live births. AGS is characterised by intrahepatic bile duct paucity and other developmental abnormalities affecting the heart, liver, eyes, vertebrae and the craniofacial region. Mutations in the JAG1 gene have been demonstrated to cause Alagille syndrome. JAG1 encodes a cellular membrane-bound ligand for the Notch receptor and is expressed during the normal development of tissues affected in Alagille syndrome. JAG1 mutations are detected in approximately 70% of AGS patients and are mostly protein truncating mutations. JAG1 mutations have also been described in patients that do not demonstrate the complete AGS phenotype, suggesting that the phenotypic spectrum of JAG1 mutations is broader than thus far assumed.