Jagged-mediated development and disease: Mechanistic insights and therapeutic implications for Alagille syndrome

Notch signaling controls multiple aspects of embryonic development and adult homeostasis. Alagille syndrome is usually caused by a single mutation in the jagged canonical Notch ligand 1 (JAG1), and manifests with liver disease and cardiovascular symptoms that are a direct consequence of JAG1 haploinsufficiency. Recent insights into Jag1/Notch-controlled developmental and homeostatic processes explain how pathology develops in the hepatic and cardiovascular systems and, together with recent elucidation of mechanisms modulating liver regeneration, provide a basis for therapeutic efforts. Importantly, disease presentation can be regulated by genetic modifiers, that may also be therapeutically leverageable. Here, we summarize recent insights into how Jag1 controls processes of relevance to Alagille syndrome, focused on Jag1/Notch functions in hepatic and cardiovascular development and homeostasis.

Diagnosis and management of Alagille and progressive familial intrahepatic cholestasis

Alagille syndrome and progressive familial intrahepatic cholestasis are conditions that can affect multiple organs. Advancements in molecular testing have aided in the diagnosis of both. The impairment of normal bile flow and secretion leads to the various hepatic manifestations of these diseases. Medical management of Alagille syndrome and progressive familial intrahepatic cholestasis remains mostly targeted on supportive care focusing on quality of life, cholestasis, and fat-soluble vitamin deficiency. The most difficult therapeutic issue is typically related to pruritus, which can be managed by various medications such as ursodeoxycholic acid, rifampin, cholestyramine, and antihistamines. Surgical operations were previously used to disrupt enterohepatic recirculation, but recent medical advancements in the use of ileal bile acid transport inhibitors have shown great efficacy for the treatment of pruritus in both Alagille syndrome and progressive familial intrahepatic cholestasis.

The Curious Case of Alagille Syndrome: A Case Report With NANDA-I Classification, NIC, and NOC Linkage to the Patient Care Plan

Alagille syndrome is a rare and complex pleiotropic multisystem disorder caused by an autosomal dominant genetic mutation of JAG1 (90%) and NOTCH2 (1%-2%) genes located on the short arm of chromosome 20. This case is reported as per the CA se RE ports (CARE) guidelines (2013). A 14-year-old boy who is a known case of chronic cholestatic liver disease of neonatal onset, was diagnosed with Alagille syndrome as evident from a NOTCH 2 mutation in genetic analysis and paucity of intrahepatic bile ducts on biopsy. He presented with portal hypertension, growth failure, and persistent hyperbilirubinemia. This case highlights the gamut of multisystem dysfunctions faced by this child. He is currently on conservative management and worked up for liver transplantation. The condition is often rare and challenging due to the multisystem pathogenesis. Thus, the nursing care is also multifaceted. This case study identified relevant North American Nursing Diagnosis Association (NANDA) Classification, Nursing Interventions Classification (NIC), and Nursing Outcomes Classification (NOC) concepts to describe care of children with Alagille syndrome based on actual patient data.

Management of adults with Alagille syndrome

Alagille syndrome (ALGS) is a complex rare genetic disorder that involves multiple organ systems and is historically regarded as a disease of childhood. Since it is inherited in an autosomal dominant manner in 40% of patients, it carries many implications for genetic counselling of patients and screening of family members. In addition, the considerable variable expression and absence of a clear genotype-phenotype correlation, results in a diverse range of clinical manifestations, even in affected individuals within the same family. With recent therapeutic advancements in cholestasis treatment and the improved survival rates with liver transplantation (LT), many patients with ALGS survive into adulthood. Although LT is curative for liver disease secondary to ALGS, complications secondary to extrahepatic involvement remain problematic lifelong. This review is aimed at providing a comprehensive review of ALGS to adult clinicians who will take over the medical care of these patients following transition, with particular focus on certain aspects of the condition that require lifelong surveillance. We also provide a diagnostic framework for adult patients with suspected ALGS and highlight key aspects to consider when determining eligibility for LT in patients with this syndrome.

Alagille syndrome: understanding the genotype-phenotype relationship and its potential therapeutic impact

INTRODUCTION

Alagille syndrome (ALGS) is an autosomal dominant, multisystem genetic disorder with wide phenotypic variability caused by mutations in the Notch signaling pathway, specifically from mutations in either the Jagged1 (JAG1) or NOTCH2 gene. The range of clinical features in ALGS can involve various organ systems including the liver, heart, eyes, skeleton, kidney, and vasculature. Despite the genetic mutations being well-defined, there is variable expressivity and individuals with the same mutation may have different clinical phenotypes.

AREAS COVERED

While no clear genotype-phenotype correlation has been identified in ALGS, this review will summarize what is currently known about the genotype-phenotype relationship and how this relationship influences the treatment of the multisystemic disorder. This review includes discussion of numerous studies which have focused on describing the genotype-phenotype relationship of different organ systems in ALGS as well as relevant basic science and population studies of ALGS. A thorough literature search was completed via the PubMed and National Library of Medicine GeneReviews databases including dates from 1969, when ALGS was first identified, to February 2023.

EXPERT OPINION

The genetics of ALGS are well defined; however, ongoing investigation to identify genotype-phenotype relationships as well as genetic modifiers as potential therapeutic targets is needed. Clinicians and patients alike would benefit from identification of a correlation to aid in diagnostic evaluation and management.

Health Care Resource Utilization by Patients with Alagille Syndrome

OBJECTIVE

To assess and characterize health care resource utilization (HRU) in children with the rare, genetic, multisystem disorder, Alagille syndrome.

STUDY DESIGN

This retrospective analysis reviewed commercially insured and Medicaid-insured claims from October 1, 2015 to December 31, 2019 to assess HRU in patients with Alagille syndrome. As there is no specific International Classification ofDiseases-10 code for Alagille syndrome, patients were identified using the following algorithm: ≥1 claim with diagnosis code Q44.7 (other congenital malformations of the liver); <18 years of age, with no history of biliary atresia (International Classification ofDiseases-10 code: Q44.2); and ≥6 months of insurance eligibility prior to diagnosis. HRU was summarized per patient per year over all available claims postdiagnosis.

RESULTS

A total of 171 commercially insured and 215 Medicaid-insured patients with Alagille syndrome were available for analysis. Annually, commercially insured and Medicaid-insured patients averaged 31 medical visits (range, 1.5-237) and 48 medical visits (range, 0.7-690), respectively. The most common visits were outpatient with the majority encompassing lab/imaging and primary care visits (commercially insured: 21 [range, 0.0-183]; Medicaid-insured: 26 [range, 0.0-609]). Inpatient visits were the highest driver of costs in both the commercial and Medicaid populations.

CONCLUSIONS

Patients with Alagille syndrome have a substantial HRU burden driven largely by numerous outpatient visits and costly inpatient stays. Given the complexity and variability of Alagille syndrome presentation, patients may benefit from multidisciplinary and subspecialized care.

[Identification of a novel JAG1 mutation in a family affected by Alagille syndrome]

Alagille syndrome (ALGS) is an autosomal dominant disorder which is mainly caused by JAG1 gene mutation and can affect multiple systems including the liver, heart, eyes, skeleton and face. This paper reports the clinical and genetic features of an ALGS patient. A 2-year-and-9-month-old boy was referred to the hospital with the complaint of abnormal liver function and heart murmur discovered over two years. Jaundice of the skin and sclera was not observed. The child had a prominent forehead, left esotropia, depressed nasal bridge and micromandible. The two lungs were clear on auscultation, but a systolic cardiac murmur of grade 2/6 could be heard between the 2nd and 3rd intercostal space at the left sternal border. Neither abdominal distension nor enlarged liver or spleen was discovered. X-ray radiography uncovered butterfly malformation of the 6th and 8th thoracic vertebrae. Serum biochemistry analysis revealed elevation of total bile acids, bilirubin and transaminases. Based on the clinical characteristics and the consultation opinion of the ophthalmologist, the child was diagnosed to have ALGS with Duane retraction syndrome. DNA direct sequencing detected a novel JAG1 mutation c.2419delG(p.Glu807AsnfsX819) in the child. Symptomatic and supportive therapy was performed thereafter and clinical follow-up was conducted until he was 4 years and 2 months. In the follow-up visits, his general condition remained stable, but the facial malformations, left esotropia, cardiac murmur and abnormal liver function persistend. The long-term outcome needed to be observed.

Notch Signaling in Normal and Disease States: Possible Therapies Related to Glycosylation

The Notch signaling pathway is involved in a wide variety of highly conserved developmental processes in mammals. Importantly, mutations of the Notch protein and components of its signaling pathway have been implicated in an array of human diseases (T-cell leukemia and other cancers, Multiple Sclerosis, CADASIL, Alagille Syndrome, Spondylocostal Dysostosis). In mammals, Notch becomes activated upon binding of its extracellular domain to ligands (Delta and Jagged/Serrate) that are present on the surface of apposed cells. The extracellular domain of Notch contains up to 36 tandem Epidermal Growth Factor-like (EGF) repeats. Many of these EGF repeats are modified at evolutionarily-conserved consensus sites by an unusual form of O-glycosylation called O-fucose. Work from several groups indicates that O-fucosylation plays an important role in ligand mediated Notch signaling. Recent evidence also suggests that the enzyme responsible for addition of O-fucose to Notch, protein O-fucosyltransferase-1 (POFUT1), may serve a quality control function in the endoplasmic reticulum. Additionally, some of the O-fucose moieties are further elongated by the action of members of the Fringe family of beta-1,3-N-acetylglucosaminyltransferases. The alteration in O-fucose saccharide structure caused by Fringe modulates the response of Notch to its ligands. Thus, glycosylation serves an important role in regulating Notch activity. This review focuses on the role of glycosylation in the normal functioning of the Notch pathway. As well, potential roles for glycosylation in Notch-related human diseases, and possible roles for therapeutic targeting of POFUT1 and Fringe in Notch-related human diseases, are discussed.

A case of Takayasu disease with findings of incomplete Alagille syndrome

A 16-year-old girl being followed up for Takayasu arteritis for the last 3 years was also found to have Alagille syndrome upon findings of atypical facies, posterior embryotoxon, high-pitched voice, osteopenia and hypogonadism. This case might imply a possible relationship between Takayasu arteritis and Alagille syndrome.

Clinical problems with developmental anomalies of the biliary tract

Cholestatic jaundice defined as conjugated hyperbilirubinemia is a typical feature of neonatal liver disease. Biliary atresia is the most common disorder producing cholestasis during the first 2 months of life. Syndromic and non-syndromic paucity of the intralobular bile ducts and choledochal cysts can also present with cholestasis during early life. Liver dysfunction from obstruction of the biliary tree must be differentiated from numerous disorders affecting hepatocytes such as congenital infection and inborn errors of metabolism. Early recognition and a stepwise diagnostic evaluation of the cholestatic infant are essential in successfully treating many metabolic and infectious liver diseases of the infant as well as surgically relieving obstruction in patients with biliary atresia.

Heritable disorders of the bile ducts

Diseases of the bile ducts encompass a wide range of disorders. These include those disorders primarily affecting extra and intrahepatic bile ducts and those that may be classified as panbiliary. The major heritable bile duct disorders are those affecting the intrahepatic ducts, namely syndromic bile duct paucity, or Alagille syndrome, and the fibrocystic cholangiopathies autosomal recessive polycystic kidney disease/congenital hepatic fibrosis, and autosomal dominant polycystic kidney disease. This discussion focuses on heritable disorders of the bile ducts.

Interventional strategies in the management of peripheral pulmonary artery stenosis

Peripheral pulmonary artery stenosis challenges therapeutic algorithms for the management of congenital heart malformations. Surgical repair of the proximal pulmonary artery lesion remains with a high recurrence rate while the distal lesions are difficult to access. With the development of transcatheter interventional strategies in the early 1980s, a number of transcatheter treatment options became available. In this review, we summarize the current state of the art for interventional strategies in the management of peripheral pulmonary artery stenosis.

Alagille syndrome

Alagille syndrome (AGS) was described more than 35 years ago as a genetic entity characterised by five major features: chronic cholestasis owing to paucity of interlobular bile ducts; peripheral pulmonary stenosis; butterfly like vertebral arch defect; posterior embryotoxon and peculiar facies. AGS has long been said to have a relative good prognosis but overall survival at twenty years averages 70%. Complex congenital heart disease and hepatic disease with or without liver transplantation contribute significantly to mortality. JAGGED1 has been identified as a responsible gene by demonstration of mutations in AGS patients. Studies of JAGGED1 expression pattern demonstrate that minor features and almost all the elements in the long list of manifestations described in AGS patients are not coincidental. This suggests that Alagille syndrome definition may be revisited in the light of JAGGED1 mutations.

A case report: Alagille syndrome

Alagille syndrome consists of 5 major features comprising paucity of interlobular bile ducts, characteristic facies, posterior embryotoxon, vertebral defects and peripheral pulmonic stenosis. The female patient in this report met 4 of the 5 major features except ocular abnormality. The first clinical presentations were prolonged jaundice and generalized ecchymoses. She was treated by plasma replacement and vitamin supplement, particularly vitamin K1, which produced clinical improvement. This report also reviews the literature of Alagille syndrome.

Arteriohepatic dysplasia (Alagille syndrome; Watson-Alagille syndrome)

Alagille syndrome (AS) (arteriohepatic dysplasia, Alagille-Watson syndrome) is a multi-system disorder with hepatic, skeletal, eye, cardiac and renal manifestations. It results from mutation of the JAG1 gene, located on chromosome 20, which encodes a ligand for Notch receptor(s). The interactions of Notch receptors and their ligands are crucial in controlling cell fate decisions in a variety of developmental processes. AS varies in its severity, even in the same family, from asymptomatic gene carriers through to lethality due to inoperable cardiac or end-stage liver disease. However, advances in medical and surgical therapy have improved the prognosis at the severe end of the spectrum. It is hoped that the enhanced understanding of the biology of AS resulting from the cloning of the JAG1 gene will enable us to develop additional strategies for more effective treatments.

Metabolic liver disease in the pediatric patient

Most metabolic liver diseases that affect pediatric patients present in the neonatal period with either cholestasis or acute liver failure. Metabolic liver disease in the older child has considerable overlap with adult patients. New diagnostic methods and therapy, including liver transplantation, has radically changed the outcome of many metabolic liver diseases.

Alagille syndrome today

A genetic syndrome causing paucity of interlobular bile ducts (Alagille syndrome) is characterized by five main characteristics: typical, peculiar facies; chronic cholestasis; posterior embryotoxon; butterfly-like vertebral-arch defects; and cardiovascular malformations. In the complete form of the syndrome, all five features are observed. Four or less of these characteristics are present in the incomplete or partial forms of this syndrome. Other, less frequent characteristics (growth retardation, mental retardation, renal and bone abnormalities as well as a high-pitched voice) have also been observed. An autosomal dominant mode of genetic transmission with variable penetrance seems likely. Therapy consists of nutritional supplementation of medium-chain triglycerides, essential fatty acids and fat-soluble vitamins. Liver transplantation has been used successfully to treat patients with liver failure, portal hypertension or severe pruritus and xanthomatosis.