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JAGGED1 gene variations in Chinese twin sisters with Alagille syndrome.

ABSTRACT: Variations in the JAGGED1 gene have been found to cause Alagille syndrome. Nevertheless, no particular hotspots in the gene have been found; any part of the entire coding regions for JAGGED1 may be involved. Twin sisters with jaundice visited our hospital and were diagnosed with Alagille syndrome. The gene variations in their JAGGED1 coding sequences were evaluated by complementary DNA sequencing. The 12-month-old twin sisters have broad foreheads, deep-set eyes, pointed chins, and triangular faces with jaundice. Clinical testing showed the presence of posterior embryotoxon, butterfly vertebrae, and atrial septal defect. Biochemical indexes showed cholestasis and liver damage. Three conserved variations were identified within exons 22 (c.2612C>G), 24 (c.2957T>A), and 26 (c.3417T>C) in the JAGGED1 coding sequence. The predicted consequences for c.2612C>G, c.2957T>A, and c.3417T>C were p.Pro871Arg, p.Leu986*, and p.Tyr1139=, respectively. The T to A change in the JAGGED1 coding sequence at 2957 will generate a stop codon and might lead to deletion of amino acid 233 at the C terminal of the JAGGED1 protein. Our data suggest that gene variations of c.2612C>G, c.2957T>A, and c.3417T>C, especially c.2957T>A, might have contributed to the pathogenesis of Alagille syndrome in these Chinese twin sisters and provided new gene evidences for Alagille syndrome.

SUBMITTER: Xie X

PROVIDER: S-EPMC4555753 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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JAGGED1 gene variations in Chinese twin sisters with Alagille syndrome.

Xie Xinbao X Lu Yi Y Wang Xiaohong X Wu Bingbing B Yu Hui H

International journal of clinical and experimental pathology 20150701 7

Variations in the JAGGED1 gene have been found to cause Alagille syndrome. Nevertheless, no particular hotspots in the gene have been found; any part of the entire coding regions for JAGGED1 may be involved. Twin sisters with jaundice visited our hospital and were diagnosed with Alagille syndrome. The gene variations in their JAGGED1 coding sequences were evaluated by complementary DNA sequencing. The 12-month-old twin sisters have broad foreheads, deep-set eyes, pointed chins, and triangular fa ...[more]

PMID: 26339425

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Project description:Background & aimsAlagille syndrome is a genetic disorder characterized by cholestasis, ocular abnormalities, characteristic facial features, heart defects, and vertebral malformations. Most cases are associated with mutations in JAGGED1 (JAG1), which encodes a Notch ligand, although it is not clear how these contribute to disease development. We aimed to develop a mouse model of Alagille syndrome to elucidate these mechanisms.MethodsMice with a missense mutation (H268Q) in Jag1 (Jag1+/Ndr mice) were outbred to a C3H/C57bl6 background to generate a mouse model for Alagille syndrome (Jag1Ndr/Ndr mice). Liver tissues were collected at different timepoints during development, analyzed by histology, and liver organoids were cultured and analyzed. We performed transcriptome analysis of Jag1Ndr/Ndr livers and livers from patients with Alagille syndrome, cross-referenced to the Human Protein Atlas, to identify commonly dysregulated pathways and biliary markers. We used species-specific transcriptome separation and ligand-receptor interaction assays to measure Notch signaling and the ability of JAG1Ndr to bind or activate Notch receptors. We studied signaling of JAG1 and JAG1Ndr via NOTCH 1, NOTCH2, and NOTCH3 and resulting gene expression patterns in parental and NOTCH1-expressing C2C12 cell lines.ResultsJag1Ndr/Ndr mice had many features of Alagille syndrome, including eye, heart, and liver defects. Bile duct differentiation, morphogenesis, and function were dysregulated in newborn Jag1Ndr/Ndr mice, with aberrations in cholangiocyte polarity, but these defects improved in adult mice. Jag1Ndr/Ndr liver organoids collapsed in culture, indicating structural instability. Whole-transcriptome sequence analyses of liver tissues from mice and patients with Alagille syndrome identified dysregulated genes encoding proteins enriched at the apical side of cholangiocytes, including CFTR and SLC5A1, as well as reduced expression of IGF1. Exposure of Notch-expressing cells to JAG1Ndr, compared with JAG1, led to hypomorphic Notch signaling, based on transcriptome analysis. JAG1-expressing cells, but not JAG1Ndr-expressing cells, bound soluble Notch1 extracellular domain, quantified by flow cytometry. However, JAG1 and JAG1Ndr cells each bound NOTCH2, and signaling from NOTCH2 signaling was reduced but not completely inhibited, in response to JAG1Ndr compared with JAG1.ConclusionsIn mice, expression of a missense mutant of Jag1 (Jag1Ndr) disrupts bile duct development and recapitulates Alagille syndrome phenotypes in heart, eye, and craniofacial dysmorphology. JAG1Ndr does not bind NOTCH1, but binds NOTCH2, and elicits hypomorphic signaling. This mouse model can be used to study other features of Alagille syndrome and organ development.

Dataset Information

JAGGED1 gene variations in Chinese twin sisters with Alagille syndrome.

Publications

JAGGED1 gene variations in Chinese twin sisters with Alagille syndrome.

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