Diagnostic Test Directory

Molecular Genetics Laboratory

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Alagille Syndrome (JAG1 Known Point Mutation Analysis)

  • LIS Mnemonic: MBJAG1PT


    Collect whole blood in a purple top (EDTA) tube.

    Volume Required

    5 ml whole blood or 1 ug DNA

    Minimum Required

    3 ml


    Refrigerate sample until shipment. Send the sample at room temperature with overnight delivery for receipt Monday through Friday within 24 hours of collection.


    Whole blood can be refrigerated until shipment.

    Unacceptable conditions

    Heparinized specimens, severely hemolyzed specimens, frozen, clotted or possibly commingled specimens, blood in non-sterile or leaky containers, mislabeled or inappropriately labeled specimens.

    Specimen Handling

    Do not heat, freeze or centrifuge blood before shipment. Refrigerate sample until shipment.

Days Performed

Mon - Fri 9:00am to 4:00pm


2-3 weeks



Disease Information

Clinical Features:

Alagille syndrome(AGS) is a multisystem disorder characterized by the histologic finding of bile duct paucity on liver biopsy, cholestasis, cardiac defects (stenosis of pulmonary artery), butterfly vertebrae and ophthalmologic abnormalities (posterior embryotoxon). Characteristic facial features include a prominent forehead, deep set eyes with mild hypertelorism, pointed chin, and saddle or straight nose with a bulbous tip. Renal, pancreatic and central nervous system abnormalities are also observed in some patients. The clinical features are variable even within the same family.

Molecular Genetics:

Mutations in the JAG1 gene are associated with the majority of cases of AGS. JAG1 is located on chromosome 20p12 and it encodes a highly conserved cell surface protein that is part of the Notch signaling pathway thought to regulate cell fate decisions in many cell types. The JAG1 protein acts as a ligand for the Notch transmembrane receptors.

Test Methods:

Sequence analysis of the mutation previously identified in a family member will be performed.

Detection Rate:

Sequence analysis of the JAG1 detects point mutations in 89% of patients with a clinical diagnosis of AGS (Crosnier et al. 1999, Krantz et al. 1998, Spinner et al. 2001, Warthen et al. 2006). Large deletions and microdeletions of 20p12 involving the JAG1 have been detected in an additional 7% of patients. Fewer than 1% of patients have a mutation in the NOTCH2 gene. About 30-50% of individuals with AGS have an affected parent. In the remaining 50-70% of patients, the mutations are de novo.


Test results with interpretation will be mailed and/or faxed to the referring physician or send out lab following completion of the test. Additional reports will be provided as requested.


The clinical utility of the assay is to support a clinical diagnosis of the disease, facilitate genetic counseling, and assess the risk to other first degree relatives and to facilitate testing of at - risk family members.

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