Search

Background: Alagille syndrome (ALGS) is a rare autosomal dominant genetic disease caused by pathogenic variants in two genes: Jagged Canonical Notch Ligand 1 ( JAG1 ) and Notch Receptor 2 ( NOTCH2 ). It is characterized by phenotypic variability and incomplete penetrance with multiorgan clinical signs., Methods: Using Next Generation Sequencing (NGS), we analyzed a panel of liver-disease-related genes in a population of 230 patients with cholestasis and hepatopathies. For the rare variants, bioinformatics predictions and pathogenicity classification were performed., Results: We identified eleven rare NOTCH2 variants in 10 patients, two variants being present in the same patient. Ten variants had never been described before in the literature. It was possible to classify only two null variants as pathogenic, whereas the most of variants were missense (8 out of 11) and were classified as uncertain significance variants (USVs). Among patients with ALGS suspicion, two carried null variants, two carried variants predicted to be pathogenic by bioinformatics, one carried a synonymous variant and variants in glycosylation-related genes, and two carried variants predicted as benign in the PEST domain., Conclusions: Our results increased the knowledge about NOTCH2 variants and the related phenotype, allowing us to improve the genetic diagnosis of ALGS.

BACKGROUND Alagille syndrome (ALGS) is a multisystem hereditary illness with a dominant pattern and partial penetrance. Multiple organ abnormalities can be caused by mutations in the Jagged canonical Notch ligand 1 (JAG1) gene. Notch receptor 2 (NOTCH2) gene mutations are also uncommon. ALGS is also characterized by deformed or narrowed bile ducts and is notoriously difficult to diagnose due to the wide range of symptoms and absence of unambiguous genotype-phenotype connections. Little is known about ALGS patients who have NOTCH2 mutations. We present a patient who developed progressive liver failure due to a unique pathogenic heterozygous variation of the NOTCH2 gene, c.1076c>T p. (Ser359Phe) chr1: 120512166, resulting in type 2 ALGS. CASE REPORT A Saudi Arabian newborn with bilateral hazy eyes, ectropion, dry ichthyic skin, normal male genitalia, and bilateral undescended testes was born at 31 weeks. Previous miscarriages, pregnancy-induced maternal cholestasis, fatty liver, or neonatal jaundice were not reported in the family history. He had developed worsening cholestatic jaundice by the third week of hospitalization. The extensive work-up for metabolic, infectious, and other relevant etiologies was negative. Following gram-negative sepsis, he died of multiorgan failure. A NOTCH2 gene mutation explained the phenotypic difference in our situation. Another intriguing observation was the presence of ichthysis and craniosynostosis in ALGS with a NOTCH2 mutation. CONCLUSIONS Cholestasis in newborns can be difficult to diagnose. Next-generation sequencing detects 112 copy number variants in the cholestasis gene panel blood test. More research is needed to understand why NOTCH2 mutations are relatively rare in ALGS.

Alagille syndrome (ALGS) is a complex heterogenous disease with a wide array of clinical manifestations in association with cholestatic liver disease. Major clinical and genetic advancements have taken place since its first description in 1969. However, clinicians continue to face considerable challenges in the management of ALGS, particularly in the absence of targeted molecular therapies. In this article, we provide an overview of the broad ALGS phenotype, current approaches to diagnosis and with particular focus on key clinical challenges encountered in the management of these patients., Competing Interests: Disclosure B.M. Kamath is a Consultant for Mirum, Albireo, Audentes and Third Rock Ventures. The author receives unrestricted educational grant funding from Mirum and Albireo. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the article, or in the decision to publish the results. M.D. Ayoub has nothing to disclose., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background and Aims: Alagille syndrome (ALGS) type 2 caused by mutations in NOTCH2 has genotypic and phenotypic heterogeneity. Diagnosis in some atypical patients with isolated hepatic presentation could be missed., Methods: Using 2087 patients with paediatric liver manifestations, NOTCH2 allele frequencies, in-silico prediction, protein domains and clinical features were analysed to define the pathogenicity of NOTCH2 variants for diagnosis of ALGS type 2., Results: Among 2087 patients with paediatric liver manifestations, significantly more NOTCH2 variants were absent in gnomAD in patients with elevated γ-glutamyltransferase (GGT) (p = .041). Significantly more NOTCH2 variants which were absent in gnomAD were located in protein functional domains (p = .038). When missense variants were absent in gnomAD and predicted to be pathogenic by at least three out of seven in-silico tools, they were found to be significantly associated with liver manifestations with elevated GGT (p = .003). Comparing this to patients with likely benign (LB) variants, the patients with likely-pathogenic (LP) variants have significantly more liver manifestations with elevated GGT (p = .0001). Significantly more patients with LP variants had extra-hepatic phenotypes of ALGS compared with those patients with LB variants (p = .0004)., Conclusion: When NOTCH2 variants are absent in gnomAD, null variants and missense variants which were predicted to be pathogenic by at least three in-silico tools could be considered pathogenic in patients with high GGT chronic liver diseases., (© 2022 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Alagille syndrome (ALGS) is a rare multisystem disorder caused by mutations in the JAG1 or NOTCH2 gene. However NOTCH2 gene mutations were rarely found in the Alagille patients. Little is known about the clinical and pathological profiles about Alagille patients with NOTCH2 mutation., Case Report: Our case described a 16-year-old female patient manifesting as recurrent jaundice and abnormal liver function from the second week of her birth. She presented a butterfly vertebrae and typical facial features including a prominent forehead, deep-set eyes, a pointed chin, and a straight nose with bulbous tip. Pathogenic heterozygous c.5857 C > T variant in NOTCH2 gene was found. Her liver biopsy featured by a disorder liver structure with cholestasis and fibrosis in portal area, which is different from typical bile duct paucity reported in JAG1 deficient patients., Results: A diagnosis of ALGS was made. The patient was treated with ursodeoxycholic acid and compound embryonic bovine liver extract tablets and infusion of human serum albumin to improve her clinical and pathological symptoms., Conclusion: Since Alagille patients with NOTCH2 mutations have been rarely reported, our case will highlight the clinical and pathological profiles of these patients., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Alagille syndrome (ALGS) is a multisystem autosomal dominant developmental disorder caused predominantly by pathogenic variants in JAGGED1 (JAG1), and also by pathogenic variants in NOTCH2 in a much smaller number of individuals. Clinical presentation is highly variable and includes liver, heart, eye, skeleton, and facial abnormalities, with a subset of individuals also presenting with kidney, vascular, and central nervous system phenotypes. Hepatocellular carcinoma (HCC) is a rare complication of ALGS, though little is known about its incidence or etiology among affected individuals. Previous reports have identified HCC occurrence in both pediatric and adult cases of ALGS. We present a case report of HCC in a 58-year-old woman with a pathogenic JAG1 variant and no overt hepatic features of ALGS. Through a comprehensive literature review, we compile all reported pediatric and adult cases, and further highlight one previously reported case of HCC onset in an adult ALGS patient without any hepatic disease features, similar to our own described patient. Our case report and literature review suggest that ALGS-causing variants could confer risk for developing HCC regardless of phenotypic severity and highlight a need for a cancer screening protocol that would enable early detection and treatment in this at-risk population., (© 2020 The Authors. American Journal of Medical Genetics Part A published by Wiley Periodicals LLC.)

Alagille syndrome is an autosomal dominant disease with a known molecular etiology of dysfunctional Notch signaling caused primarily by pathogenic variants in JAGGED1 (JAG1), but also by variants in NOTCH2. The majority of JAG1 variants result in loss of function, however disease has also been attributed to lesser understood missense variants. Conversely, the majority of NOTCH2 variants are missense, though fewer of these variants have been described. In addition, there is a small group of patients with a clear clinical phenotype in the absence of a pathogenic variant. Here, we catalog our single-center study, which includes 401 probands and 111 affected family members amassed over a 27-year period, to provide updated mutation frequencies in JAG1 and NOTCH2 as well as functional validation of nine missense variants. Combining our cohort of 86 novel JAG1 and three novel NOTCH2 variants with previously published data (totaling 713 variants), we present the most comprehensive pathogenic variant overview for Alagille syndrome. Using this data set, we developed new guidance to help with the classification of JAG1 missense variants. Finally, we report clinically consistent cases for which a molecular etiology has not been identified and discuss the potential for next generation sequencing methodologies in novel variant discovery., (© 2019 The Authors. Human Mutation published by Wiley Periodicals, Inc.)

Alagille syndrome is a complex multisystem autosomal dominant disorder with a wide variability in penetrance of clinical features. A majority of patients have pathogenic mutations in either the JAG1 gene, encoding a Notch pathway ligand, or the receptor NOTCH2. No genotype-phenotype correlations have been found in any organ system. Liver disease is a major cause of morbidity in this population, whereas cardiac and vascular involvement accounts for most of the mortality. Current therapies are supportive, but the future is promising for the development of targeted interventions to augment Notch pathway signaling in involved tissues., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background & Aims: Alagille 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., Methods: Mice 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 (Jag1 Ndr/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 Jag1 Ndr/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 JAG1 Ndr to bind or activate Notch receptors. We studied signaling of JAG1 and JAG1 Ndr via NOTCH 1, NOTCH2, and NOTCH3 and resulting gene expression patterns in parental and NOTCH1-expressing C2C12 cell lines., Results: Jag1 Ndr/Ndr mice had many features of Alagille syndrome, including eye, heart, and liver defects. Bile duct differentiation, morphogenesis, and function were dysregulated in newborn Jag1 Ndr/Ndr mice, with aberrations in cholangiocyte polarity, but these defects improved in adult mice. Jag1 Ndr/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 JAG1 Ndr , compared with JAG1, led to hypomorphic Notch signaling, based on transcriptome analysis. JAG1-expressing cells, but not JAG1 Ndr -expressing cells, bound soluble Notch1 extracellular domain, quantified by flow cytometry. However, JAG1 and JAG1 Ndr cells each bound NOTCH2, and signaling from NOTCH2 signaling was reduced but not completely inhibited, in response to JAG1 Ndr compared with JAG1., Conclusions: In mice, expression of a missense mutant of Jag1 (Jag1 Ndr ) disrupts bile duct development and recapitulates Alagille syndrome phenotypes in heart, eye, and craniofacial dysmorphology. JAG1 Ndr 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., (Copyright © 2018. Published by Elsevier Inc.)

Whereas Jagged1-Notch2 signaling is known to pattern the sensorineural components of the inner ear, its role in middle ear development has been less clear. We previously reported a role for Jagged-Notch signaling in shaping skeletal elements derived from the first two pharyngeal arches of zebrafish. Here we show a conserved requirement for Jagged1-Notch2 signaling in patterning the stapes and incus middle ear bones derived from the equivalent pharyngeal arches of mammals. Mice lacking Jagged1 or Notch2 in neural crest-derived cells (NCCs) of the pharyngeal arches display a malformed stapes. Heterozygous Jagged1 knockout mice, a model for Alagille Syndrome (AGS), also display stapes and incus defects. We find that Jagged1-Notch2 signaling functions early to pattern the stapes cartilage template, with stapes malformations correlating with hearing loss across all frequencies. We observe similar stapes defects and hearing loss in one patient with heterozygous JAGGED1 loss, and a diversity of conductive and sensorineural hearing loss in nearly half of AGS patients, many of which carry JAGGED1 mutations. Our findings reveal deep conservation of Jagged1-Notch2 signaling in patterning the pharyngeal arches from fish to mouse to man, despite the very different functions of their skeletal derivatives in jaw support and sound transduction.

Background: Alagille syndrome (AGS) is a multisystem autosomal dominant disorder that affects the liver, heart, eyes, face, bone, and other organs. AGS is caused by mutations in one of two genes, JAG1 or NOTCH2. We evaluated clinical features, outcomes, and the presence of JAG1 and NOTCH2 mutations in Korean children with AGS., Methods: Between January 1997 and December 2013, 19 children were diagnosed with AGS at Asan Medical Center, Seoul, Korea. Their clinical features, outcomes, and JAG1 and NOTCH2 mutation status were retrospectively analyzed., Results: The prevalence of clinical features in the 19 patients was as follows: dysmorphic facial features, 100% (n = 19); liver symptoms, 89% (n = 17); cardiac symptoms, 95% (n = 18); ophthalmologic symptoms, 67% (n = 10); skeletal deformities, 47% (n = 9); and renal symptoms, 21% (n = 4). JAG1 mutations were identified in 14 patients. The 13 different JAG1 mutations, seven of which were novel, included four deletions, three insertions, two missense mutations, three nonsense mutations, and one indel mutation. No NOTCH2 mutations were found. Two patients who received liver transplantation due to liver failure were still alive. Two patients died of comorbidities related to AGS: one of cardiac failure and one of hepatic failure., Conclusion: This study describes the clinical characteristics of 19 Korean AGS patients with seven novel JAG1 mutations. Neonatal cholestatic jaundice was the most common initial presenting symptom; thus the presence of neonatal cholestasis warrants screening for syndromic features of AGS. Complex heart anomalies and progressive liver dysfunction resulted in significant morbidity and mortality in AGS., (© 2015 Japan Pediatric Society.)

Alagille syndrome is an autosomal dominant disorder with variable multisystem organ involvement that is caused by mutations in one of two genes in the Notch signalling pathway, JAG1 or NOTCH2. Alagille syndrome is characterized by bile duct paucity, along with at least three of the following features: cholestasis, cardiac defects, skeletal abnormalities, ocular abnormalities and characteristic facies. However, the clinical features of Alagille syndrome are highly variable, and children or adults may also present with predominantly renal findings and little or no hepatic involvement. Renal involvement occurs in 40% of JAG1-mutation-positive individuals. Renal insufficiency is common and has been specifically reported in children with Alagille syndrome who have end-stage liver disease. The role of NOTCH2 and JAG1 in formation of proximal nephron structures and podocytes might explain the observed phenotypes of renal dysplasia and proteinuria in patients with Alagille syndrome, and renal tubular acidosis may be the result of JAG1 expression in the collecting ducts. Renal vascular hypertension in patients with Alagille syndrome is explained by the widespread vasculopathy and the role of Notch signalling in vascular development. Increased awareness of Alagille syndrome amongst nephrologists may lead to more diagnoses of Alagille syndrome in patients with apparently isolated renal disease.

Notch2, but not Notch1, plays indispensable roles in kidney organogenesis, and Notch2 haploinsufficiency is associated with Alagille syndrome. We proposed that proximal nephron fates are regulated by a threshold that requires nearly all available free Notch intracellular domains (NICDs) but could not identify the mechanism that explains why Notch2 (N2) is more important than Notch1 (N1). By generating mice that swap their ICDs, we establish that the overall protein concentration, expression domain, or ICD amino acid composition does not account for the differential requirement of these receptors. Instead, we find that the N2 extracellular domain (NECD) increases Notch protein localization to the cell surface during kidney development and is cleaved more efficiently upon ligand binding. This context-specific asymmetry in NICD release efficiency is further enhanced by Fringe. Our results indicate that an elevated N1 surface level could compensate for the loss of N2 signal in specific cell contexts., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Alagille syndrome is a multisystem disorder characterized by highly variable expressivity, most frequently caused by heterozygous JAG1 gene mutations. Classic diagnostic criteria combine the presence of bile duct paucity on liver biopsy with three of five systems affected; liver, heart, skeleton, eye and dysmorphic facies. The aim of this study was to determine the prevalence and distribution of JAG1 mutations in patients referred for routine clinical diagnostic testing. Clinical data were available for 241 patients from 135 families. The index cases were grouped according to the number of systems affected (heart, liver, skeletal, eye and facies) and the mutation frequency calculated for each group. JAG1 mutations were identified in 59/135 (44%) probands. The highest mutation detection rates were observed in patients with the most frequent presenting features of Alagille syndrome; ranging from 20% (one system) to 86% (five systems). The overall mutation pick-up rate in a clinical diagnostic setting was lower than in previous research studies. Identification of a JAG1 gene mutation is particularly useful for those patients with atypical or mild Alagille syndrome who do not meet classic diagnostic criteria as it provides a definite molecular diagnosis and allows accurate genetic counselling for the family., (© 2011 John Wiley & Sons A/S.)

Alagille syndrome (AGS) is an autosomal dominant disorder characterized by bile duct paucity. It can be caused by variations in the JAG1 gene encoding a protein of Notch ligand and by variations in the NOTCH2 gene encoding a Notch receptor. In this study we identified 15 different JAG1 gene variations in 17 Chinese patients, nine of which were novel alterations including c.766G > T, c.819delC, c.826delT, c.3099_3100delCA, c.1323_1326delCTGG, c.1771_1775delGTGCGinsT, c.1868delG, c. 2791_2792insA and c.866delG. These alterations were located in the extracellular domain of JAG1, in particular in the DSL and EGF-like repeat domain. All the specific variations in five inheritance cases investigated were de novo. Furthermore, no sequence variation of NOTCH2 was detected in JAG1 alteration negative patients., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Alagille syndrome (ALGS, OMIM #118450) is an autosomal dominant disorder that affects multiple organ systems including the liver, heart, eyes, vertebrae, and face. ALGS is caused by mutations in one of two genes in the Notch Signaling Pathway, Jagged1 (JAG1) or NOTCH2. In this study, analysis of 21 Vietnamese ALGS individuals led to the identification of 19 different mutations (18 JAG1 and 1 NOTCH2), 17 of which are novel, including the third reported NOTCH2 mutation in Alagille Syndrome. The spectrum of JAG1 mutations in the Vietnamese patients is similar to that previously reported, including nine frameshift, three missense, two splice site, one nonsense, two whole gene, and one partial gene deletion. The missense mutations are all likely to be disease causing, as two are loss of cysteines (C22R and C78G) and the third creates a cryptic splice site in exon 9 (G386R). No correlation between genotype and phenotype was observed. Assessment of clinical phenotype revealed that skeletal manifestations occur with a higher frequency than in previously reported Alagille cohorts. Facial features were difficult to assess and a Vietnamese pediatric gastroenterologist was only able to identify the facial phenotype in 61% of the cohort. To assess the agreement among North American dysmorphologists at detecting the presence of ALGS facial features in the Vietnamese patients, 37 clinical dysmorphologists evaluated a photographic panel of 20 Vietnamese children with and without ALGS. The dysmorphologists were unable to identify the individuals with ALGS in the majority of cases, suggesting that evaluation of facial features should not be used in the diagnosis of ALGS in this population. This is the first report of mutations and phenotypic spectrum of ALGS in a Vietnamese population., (Copyright © 2012 Wiley Periodicals, Inc.)

Alagille syndrome (ALGS), also known as arteriohepatic dysplasia, is a multisystem disorder due to defects in components of the Notch signalling pathway, most commonly due to mutation in JAG1 (ALGS type 1), but in a small proportion of cases mutation in NOTCH2 (ALGS type 2). The main clinical and pathological features are chronic cholestasis due to paucity of intrahepatic bile ducts, peripheral pulmonary artery stenosis, minor vertebral segmentation anomalies, characteristic facies, posterior embryotoxon/anterior segment abnormalities, pigmentary retinopathy, and dysplastic kidneys. It follows autosomal dominant inheritance, but reduced penetrance and variable expression are common in this disorder, and somatic/germline mosaicism may also be relatively frequent. This review discusses the clinical features of ALGS, including long-term complications, the clinical and molecular diagnosis, and management.

Background: Alagille syndrome (ALGS) is a dominant, multisystem disorder caused by mutations in the Jagged1 (JAG1) ligand in 94% of patients, and in the NOTCH2 receptor in <1%. There are only two NOTCH2 families reported to date. This study hypothesised that additional NOTCH2 mutations would be present in patients with clinical features of ALGS without a JAG1 mutation., Methods: The study screened a cohort of JAG1-negative individuals with clinical features suggestive or diagnostic of ALGS for NOTCH2 mutations., Results: Eight individuals with novel NOTCH2 mutations (six missense, one splicing, and one non-sense mutation) were identified. Three of these patients met classic criteria for ALGS and five patients only had a subset of features. The mutations were distributed across the extracellular (N=5) and intracellular domains (N=3) of the protein. Functional analysis of four missense, one nonsense, and one splicing mutation demonstrated decreased Notch signalling of these proteins. Subjects with NOTCH2 mutations demonstrated highly variable expressivity of the affected systems, as with JAG1 individuals. Liver involvement was universal in NOTCH2 probands and they had a similar prevalence of ophthalmologic and renal anomalies to JAG1 patients. There was a trend towards less cardiac involvement in the NOTCH2 group (60% vs 100% in JAG1). NOTCH2 (+) probands exhibited a significantly decreased penetrance of vertebral abnormalities (10%) and facial features (20%) when compared to the JAG1 (+) cohort., Conclusions: This work confirms the importance of NOTCH2 as a second disease gene in ALGS and expands the repertoire of the NOTCH2 related disease phenotype.

Mutations in the JAG1 gene and the NOTCH2 gene cause Alagille syndrome. At present, however, genetic testing of Alagille syndrome is not commonly applied in clinical settings because the currently available assays are technically and financially demanding, mainly because of the size of the genes. In the present study, we optimized the highly sensitive and specific mutation scanning method automated denaturing high-performance liquid chromatography (DHPLC) to analyze the entire coding region of JAG1 and NOTCH2. The coding region was amplified by 69 primer pairs, all of which have the same cycling conditions, aliquoted on a 96-well format PCR plate. In this manner, all the exons were simultaneously amplified using a single block in a thermal cycler. We then wrote a computer script to analyze each segment of JAG1 and NOTCH2 by DHPLC in a serial manner using conditions that were optimized for each amplicon. The implementation of this screening method for JAG1 and NOTCH2 will help medical geneticists confirm their clinical impressions and provide accurate genetic counseling to the patients with Alagille syndrome and their families.

Alagille syndrome (AGS) is caused by mutations in the gene for the Notch signaling pathway ligand Jagged1 (JAG1), which are found in 94% of patients. To identify the cause of disease in patients without JAG1 mutations, we screened 11 JAG1 mutation-negative probands with AGS for alterations in the gene for the Notch2 receptor (NOTCH2). We found NOTCH2 mutations segregating in two families and identified five affected individuals. Renal manifestations, a minor feature in AGS, were present in all the affected individuals. This demonstrates that AGS is a heterogeneous disorder and implicates NOTCH2 mutations in human disease.