JAG1 variants are observed in ∼90% of Alagille syndrome patients whereas NOTCH2 variants account for additional 1–2% of individuals with Alagille syndrome (Li et al., 1997a; Oda et al., 1997; Mcdaniell et al., 2006; Kamath et al., 2012). Here, JAG1 is linked to Alagille syndrome.