Identification of a larger than 3 Mb deletion including JAG1 in an Alagille syndrome patient with a translocation t(3;20)(q13.3;p12.2).

ABSTRACT

Alagille syndrome (AGS) is an autosomal dominant, developmental disorder affecting multiple organ systems including liver, heart, vertebrae, eye and face. Recurrent deletions of the 20p12 region led to the localization, and ultimately to the identification of mutations in the Jagged1 gene (JAG1) in AGS patients. A translocation t(3;20)(q13.3;p12.2) in an AGS patient was characterized using fluorescent in situ hybridization (FISH). The involvement of 3q and 20p in this translocation was demonstrated using probes for 3q and 20p. Three overlapping YAC clones, 940D11, 953A2, and 675G11 extending to nearly 4 Mb including the JAG1 were used as probes for FISH analysis to define the translocation breakpoint. The translocated chromosome was found to have a deletion of more than 3 Mb including the entire JAG1 gene. The observation of an accompanying large deletion, revealed by molecular characterization of the t(3;20) translocation, is similar to the only other translocation reported in an AGS patient; a t(2;20) translocation was also found to have a large deletion of the JAG1 region at 20p12.