Natural history of liver disease in a large international cohort of children with Alagille syndrome: Results from the GALA study.

BACKGROUND AND AIMS: Alagille syndrome (ALGS) is a multisystem disorder, characterized by cholestasis. Existing outcome data are largely derived from tertiary centers, and real-world data are lacking. This study aimed to elucidate the natural history of liver disease in a contemporary, international cohort of children with ALGS. APPROACH AND RESULTS: This was a multicenter retrospective study of children with a clinically and/or genetically confirmed ALGS diagnosis, born between January 1997 and August 2019. Native liver survival (NLS) and event-free survival rates were assessed. Cox models were constructed to identify early biochemical predictors of clinically evident portal hypertension (CEPH) and NLS. In total, 1433 children (57% male) from 67 centers in 29 countries were included. The 10 and 18-year NLS rates were 54.4% and 40.3%. By 10 and 18 years, 51.5% and 66.0% of children with ALGS experienced ≥1 adverse liver-related event (CEPH, transplant, or death). Children (>6 and ≤12 months) with median total bilirubin (TB) levels between ≥5.0 and <10.0 mg/dl had a 4.1-fold (95% confidence interval [CI], 1.6-10.8), and those ≥10.0 mg/dl had an 8.0-fold (95% CI, 3.4-18.4) increased risk of developing CEPH compared with those <5.0 mg/dl. Median TB levels between ≥5.0 and <10.0 mg/dl and >10.0 mg/dl were associated with a 4.8 (95% CI, 2.4-9.7) and 15.6 (95% CI, 8.7-28.2) increased risk of transplantation relative to <5.0 mg/dl. Median TB <5.0 mg/dl were associated with higher NLS rates relative to ≥5.0 mg/dl, with 79% reaching adulthood with native liver ( p < 0.001). CONCLUSIONS: In this large international cohort of ALGS, only 40.3% of children reach adulthood with their native liver. A TB <5.0 mg/dl between 6 and 12 months of age is associated with better hepatic outcomes. These thresholds provide clinicians with an objective tool to assist with clinical decision-making and in the evaluation of therapies.

Alagille Syndrome and Chronic Arthritis: An International Case Series.

We describe 10 children with Alagille syndrome and inflammatory arthritis. In our centers, the prevalence of chronic arthritis in patients with Alagille syndrome is approximately 50 times higher compared with the general population. Arthritis was refractory to most treatment. Patients with Alagille syndrome should routinely be screened for musculoskeletal symptoms.

JAG1 loss­of­function mutations contributed to Alagille syndrome in two Chinese families.

Alagille syndrome (ALGS) is primarily caused by jagged1 (JAG1) mutations, 70% of which are protein­truncating mutations. However, no mutation hotspots have been discovered, and the pathogenic mechanism is not fully understood. The aim of the present study was to analyze two protein­truncating JAG1 mutations detected in three Chinese ALGS patients. Mutation c.1261delT (p.Cys421Valfs) was identified in one patient with hepatic damage, xanthomas, facial abnormalities and cardiovascular defects, which was inherited from his father. The other mutation, c.1382_1383delAC (p.Asp461Glyfs), carried by a pair of monozygotic twins with hepatic damage, facial abnormalities and cardiovascular defects, was de novo. Biological experiments were performed to study the characteristics and function of these mutations. The p.Cys421Valfs and p.Asp461Glyfs mutant proteins appeared to be truncated in western blotting using anti­Flag bound to the N­terminus of JAG1. The RBP­Jκ­responsive reporter gene assay was used to investigate the ability of mutant JAG1 proteins to activate the Notch signaling pathway. The mutant proteins had a lower luciferase activity than the wild­type, indicating impaired transcriptional activation ability. Western blotting using soluble JAG1 from the culture medium revealed that the expression levels of the mutant proteins were lower than that of the wild­type, suggesting that less mutant JAG1 protein underwent proteolytic cleavage than the wild­type. In conclusion, these two loss­of­function JAG1 mutations may be associated with ALGS manifestations in these patients.

Systematic Review: The Epidemiology, Natural History, and Burden of Alagille Syndrome.

BACKGROUND AND AIM: Alagille syndrome (ALGS) is an inherited multisystem disorder typically manifesting as cholestasis, and potentially leading to end-stage liver disease and death. The aim of the study was to perform the first systematic review of the epidemiology, natural history, and burden of ALGS with a focus on the liver component. METHODS: Electronic databases and proceedings from key congresses were searched in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2009 guidelines. This analysis included publications reporting epidemiology, natural history, economic burden or health-related quality of life (HRQoL) outcomes in patients with ALGS. RESULTS: Of 525 screened publications, 20 met the inclusion criteria. Liver-related features included cholestasis (87%-100% of patients), jaundice (66%-85%), and cirrhosis (44%-95%). Between 15% and 47% of patients underwent liver transplantation and 4% to 14% received partial biliary diversion. Pruritus affected the majority of patients (59%-88%, of whom up to 45% had severe pruritus) and manifested during the first 10 years of life. Children with ALGS had significantly impaired HRQoL compared with healthy controls and those with other diseases. Itching was the symptom that most affected children with ALGS. No study assessed the economic burden of ALGS. CONCLUSIONS: Our findings consolidate information on the clinical course of ALGS, and highlight gaps in knowledge, most notably the absence of any research on the economic consequences of the disease. Further research is needed to establish the incidence of genetically confirmed ALGS. Disease-specific tools are also needed to improve the measurement of symptoms, such as itching, and better understand the impact of ALGS on HRQoL.

Ocular findings in patients with cholestatic disorders of infancy: A single-centre experience.

BACKGROUND AND STUDY AIMS: Neonatal cholestasis can be associated with ocular findings that might aid in its diagnosis, e.g., Alagille syndrome (AGS) and Niemann Pick disease (NPD). We aimed to investigate the frequency of ocular manifestations in infants with cholestasis. PATIENTS AND METHODS: This cross-sectional study included cholestatic infants presenting to the Paediatric Hepatology Unit, Cairo University Paediatric Hospital, Cairo, Egypt. All infants underwent examination of lid, ocular motility, anterior and posterior segments and measurement of intraocular pressure, cycloplegic refraction, ocular ultrasonography and vision. RESULTS: The study included 112 infants with various cholestasis; 73 (65.2%) were males. The median age was 2months. Diagnosis was reached in 39 cases: 14 had AGS, 14 had biliary atresia (BA), 4 had NPD, 4 had post-haemolytic cholestasis, 2 had cytomegalovirus neonatal hepatitis, and one case had hepatorenal tyrosinaemia. Thirteen cases were probably having progressive familiar intrahepatic cholestasis (PFIC) type 1 or 2 considering their persistent cholestasis in the presence of normal gamma-glutamyl transpeptidase; 28 were left with a diagnosis of "idiopathic neonatal hepatitis" (INH), and 32 (28.6%) had no definite diagnosis. Ophthalmologic abnormalities were found in 39 cases (34.8%). The commonest finding was unilateral/bilateral optic nerve drusen in 12 (10.7%), followed by posterior embryotoxon in 11 (9.8%). Ocular findings were observed in 64.3% patients with AGS, 50% patients with NPD, 30.8% cases with suspected PFIC type 1or 2, 28.6% infants with INH, and 14.3% patients with BA. CONCLUSION: Ophthalmologic findings are not uncommon among cholestatic infants. Ophthalmologic examination should be routinely performed, including assessment of anterior segment, fundus examination, and ocular ultrasound.

Abdominal Arterial Anomalies in Children With Alagille Syndrome: Surgical Aspects and Outcomes of Liver Transplantation.

OBJECTIVES: Angiogenic defects secondary to gene mutations of JAG1 and NOTCH2, causing arterial anomalies in Alagille syndrome (AGS), are well described in the literature. The study analyzes the frequency of abdominal arterial anomalies in children with AGS with an emphasis on outcomes following liver transplantation (LT). METHODS: Between 1988 and 2013, 242 children with AGS were treated at our institution. We performed a retrospective analysis of 55 who underwent LT during the study period. Preoperative abdominal arterial findings, operative reports, arterial reconstruction technique, and early as well as late complications following LT were reviewed specifically focusing on arterial thrombosis. RESULTS: Twenty-five patients had preoperative imaging available for analysis. Twelve of these patients showed celiac trunk stenosis (48.0%), 2, a superior mesenteric artery stenosis (8.0%) and one a stenosis of both renal arteries. Twenty patients (36.3%) underwent standard hepatic reconstruction using the native recipient hepatic artery. Thirty-five patients (63.7%) underwent aortic conduit reconstruction (ACR) from the infrarenal aorta using donor arterial conduits. Hepatic artery thrombosis occurred in 9 patients (16.3%). This number was higher in the standard arterial anastomosis group 7/20 (35.0%) than in those with ACR 2/35 (5.7%, P = 0.0079). CONCLUSIONS: In this series, children with AGS pretransplant have a high prevalence of abdominal arterial anomalies. Preoperative abdominal vascular imaging makes it possible to anticipate whether or not a classical arterial revascularization can be performed or whether an ACR is required.

The prevalence of congenital heart defects in infants with cholestatic disorders of infancy: a single-centre study.

BACKGROUND: There is deficiency of data about congenital heart defects (CHDs) in cholestatic disorders of infancy other than Alagille syndrome (AGS). We aimed to define the prevalence and types of CHDs in infants with various causes of cholestatic disorders of infancy. METHODS: This cross-sectional study was conducted on 139 infants presenting with cholestasis whether surgical or non-surgical. The study was carried out at the Pediatric Hepatology Unit, Cairo University Children's Hospital, Egypt. Full examination and investigations were done in an attempt to reach an aetiologic diagnosis for cholestasis, in addition to a comprehensive echocardiographic study. RESULTS: The age at the onset of cholestasis ranged from 1 day to 7 months. Males constituted 61.2%. Biliary atresia (BA) was diagnosed in 39 patients (28%), AGS in 16 patients (11.5%), 27 patients had miscellaneous diagnoses and 57 cases had indeterminate aetiology. CHDs were detected in 55 patients (39.5%). Shunt lesions were detected in 24 patients (43.6%), pulmonary stenosis in 18 patients (32.7%) and combined lesions in 9 patients (16.4%). Three patients (5.5%) had abnormal cardiac situs. Only seven patients had clinical presentation suggestive of CHD. CHDs were detected in 14 patients with BA (35.9%), 15 patients with AGS (93.7%) and 26 patients in the remaining group (30.9%). CONCLUSION: CHDs are not uncommon among cholestatic infants and are mostly asymptomatic. Echocardiographic examination of cholestatic infants is recommended particularly for patients with BA before undergoing hepatic portoenterostomy as presence of CHD may impact the anaesthetic planning and affect the outcome of hepatobiliary surgery.

Low incidence of alpha-1-antitrypsin deficiency in Iranian patients with neonatal cholestasis.

BACKGROUND/AIMS: There is little data concerning the incidence of alpha-1-antitrypsin"(AAT) deficiency, the most common genetic cause of liver disease, among children with neonatal cholestasis in Iran. Thus, this study was performed to analyze AAT deficiency in this group of patients. MATERIALS AND METHODS: DNA samples from patients with neonatal cholestasis were investigated for Pi S and Pi Z alleles, using polymerase chain reaction-restriction fragment length polymorphism. RESULTS: Thirty patients with neonatal cholestasis were enrolled. Among those who underwent biopsies, the results revealed neonatal hepatitis in 19, bile duct paucity in 1, steatohepatitis in 1, bile duct proliferation in 1, cirrhosis in 2, fibrosis in 2, and extrahepatic biliary atresia in 1 patient. No mutant allele was found in any patient. CONCLUSION: The incidence of AAT deficiency is very low in Iran; therefore, screening for AAT is not recommended for patients with neonatal cholestasis in Iran.

Clinical features, outcomes, and genetic analysis in Korean children with Alagille syndrome.

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.

Síndrome de Alagille experiencia clínica de catorce casos en Medellín, Colombia / Alagille syndrome, clinical experience of fourteen cases in Medellin, Colombia

Introducción: El Síndrome de Alagille corresponde a una alteración autosómica dominante con expresión variable. Se caracteriza por colestasis crónica con escasez de los conductos biliares interlobulares asociada a alteraciones cardiovasculares, oftálmicas, sistema esquelético, riñones y facies característica. Su distribución es mundial con frecuencia de 1 por cada 100000 nacidos vivos. Objetivo: Describir las características clínicas, la evolución y la sobrevida de catorce pacientes, con diagnóstico de Síndrome de Alagille atendidos en un período de 16 años en Medellín, Colombia. Materiales y métodos: Es un trabajo observacional descriptivo de reporte de casos de los hallazgos morfológicos y la evolución de los pacientes con diagnóstico de Síndrome de Alagille. Resultados: Grupo compuesto por ocho niños y seis niñas, con edades entre los dos meses y los diez años al momento de diagnóstico. El síndrome completo se presentó en 28%. Los hallazgos más frecuentes, estenosis valvular de la arteria pulmonar y la alteración vertebral se presentaron en el 79%. Tres pacientes 21%, fallecieron, uno de ellos después de recibir trasplante hepático. De los once sobrevivientes dos niñas fueron sometidas a trasplante y se encuentran en buenas condiciones. Los nueve restantes padecen hepatopatía colestásica crónica y reciben tratamiento médico. Conclusión: El Síndrome de Alagille se debe tener en cuenta en el diagnóstico de colestasis crónica infantil. Para establecer la distribución y frecuencia de esta enfermedad en nuestro país es necesario desarrollar investigaciones que idealmente incluyan el estudio de la mutación genética en los pacientes y su familia cercana.

Introduction: The Alagille Syndrome is an autosomic dominant disorder with variable expression. Chronic cholestasis, characteristic facial appearance and abnormalities heart, skeleton, eye, kydnes with hypoplasia of the biliary ducts. Initial description in France, with mundial distribution her frecuence is 1/100000. Objective: To describe the clinical characteristic and evolutions of fourteen patients with diagnosis Alagille Syndrome in Medellín Colombia. Materials and methods: Descriptive retrospective study with variables obtained from clinical records of patients with diagnosis Alagille Syndrome. Results: Eight boys and six girls. The age at diagnosis varied two months at nine years. Complete syndrome was present in 28%. The most frecuent alterations were valvular stenosis pulmonary artery and failure of anterior vertebral arch fusion (butterfly vertebrae) 79%. The clinical evolution was variable, death occurred in three patients 21%, one girl post liver transplantation. Nine children had chronic hepatopathy controlled with medical treatment and two girls had liver transplantation with satisfactory evolution. Conclusions: In Colombia, the poblational incidence is not defined it is necessary to know the distribution of syndrome at future study.

Biliary disease in children.

Biliary diseases in children are infrequent; however, they can be associated with high morbidity and mortality if an accurate diagnosis is not made and adequate treatment provided in a timely fashion. Biliary atresia, choledochal cysts, gallbladder disease, and Alagille syndrome can be associated with similar clinical symptoms, laboratory findings, and radiographic findings, which makes accurate diagnosis difficult. The correct treatment for each of these clinical entities is different and can significantly reduce morbidity and mortality from these diseases. In this article, we discuss the epidemiology, approach to diagnosis, prognosis, and treatment modalities for these four disease processes.

Management of large hepatocellular carcinoma in adult patients with Alagille syndrome: a case report and review of literature.

BACKGROUND: Alagille syndrome is a multi-system developmental disorder associated with paucity of interlobular bile ducts and cholestasis, rarely associated with hepatocellular carcinoma. Associated syndromic co-morbidities may complicate surgical management. As such, we herein review the modern management of a large hepatocellular carcinoma in an adult patient with Alagille syndrome and review the literature of adult Alagille patients with hepatocellular carcinoma. CASE PRESENTATION: A 29-year-old woman with a history of Alagille syndrome was referred with biopsy-proven 12 × 8 cm hepatocellular carcinoma replacing her right liver. Biopsy of the contralateral liver demonstrated findings consistent with Alagille syndrome, but no underlying cirrhosis. CT volumetrics demonstrated a future liver remnant of 40%. Extensive hematologic and cardiac work-up was performed pre-operatively, given the syndrome's associated bleeding dyscrasias and cardiac abnormalities. The patient underwent a margin-negative right hepatectomy using the "hanging" technique through a thoracoabdominal approach. The patient developed a transient hyperbilirubinemia but no hepatic insufficiency and did well post-operatively. CONCLUSION: Since Alagille syndrome affects multiple organ systems, preoperative evaluation of cardiac, hematologic, and hepatic function should be considered. This case illustrates the peri-operative management of an Alagille patient, and highlights several key technical points that contributed to a successful resection.

Serum lipids in parents and siblings of children with Alagille syndrome: a pilot study.

BACKGROUND/AIMS: Alagille syndrome, a dominant inherited disorder, is characterized by cholestatic liver disease, associated to interlobular bile duct paucity combined with; cardiac, skeletal, ocular and facial abnormalities. Increased levels of serum lipids are present in more than 80% of probands. Parents and siblings of children with Alagille syndrome are often found to have a mild expression of this probable disease gene; it is not known if dyslipidemia occurs in parents and siblings of children with Alagille syndrome. The aim of the study was to investigate the lipid profile in sibs and parents of children with Alagille syndrome. METHODOLOGY: Four children with Alagille syndrome and 21 first-degree relatives were studied. SETTING: A pediatric referral hospital. PERIOD: July-October 2005. DESIGN: cross-sectional. VARIABLES: Total, low-density, high-density cholesterol and triglyceride. STATISTICS: chi2, Mann-Whitney U and Kruskal-Wallis. RESULTS: Probands had higher levels of total cholesterol, low-density cholesterol and triglycerides than their siblings (p<0.05); however, no differences with their parents were observed (p>0.05). CONCLUSIONS: Dyslipidemia does not seem to be a phenotypic expression in first degree relatives of children with Alagille syndrome. The increased level of serum lipids observed in some of the parents is similar to the expected prevalence of hypercholesterolemia in the adult Mexican population.

Evaluation of risk for atherosclerosis in Alagille syndrome and progressive familial intrahepatic cholestasis: two congenital cholestatic diseases with different lipoprotein metabolisms.

OBJECTIVES: To evaluate the risk for atherosclerosis in Alagille syndrome (AGS) and progressive familial intrahepatic cholestasis (PFIC) on the basis of lipoprotein metabolism and by ultrasonography. STUDY DESIGN: Five patients with AGS and 5 with PFIC, ages 3 to 4 years, were enrolled. Intimal-medial thickness and wall stiffness of the common carotid artery were examined by ultrasonography. Serum levels of lipids and lipoproteins were determined. Further, the chemical composition of LDL and its ability to transform macrophages into foam cells were determined. RESULTS: Intimal-medial thickness and wall stiffness were increased in patients with PFIC but not in patients with AGS. Total cholesterol, LDL cholesterol, HDL cholesterol, and lipoprotein X were remarkably increased in patients with AGS, whereas in patients with PFIC, an increase in triglyceride and a decrease in HDL cholesterol were the prominent findings. However, despite the normal LDL cholesterol level, oxidized LDL level was strikingly high in patients with PFIC. LDLs from patients with PFIC had high TG contents and exhibited high abilities to transform macrophages into foam cells. CONCLUSIONS: These findings suggest that patients with PFIC are at high risk for cardiovascular disorders involving atherosclerosis.

[From gene to disease: arteriohepatic dysplasia or Alagille syndrome]. / Van gen naar ziekte; arteriohepatische dysplasie--het syndroom van Alagille.

Alagille syndrome (AGS), also known as arteriohepatic dysplasia, is an autosomal dominant disorder with a prevalence of approximately one in 70,000 live births. AGS is characterised by intrahepatic bile duct paucity and other developmental abnormalities affecting the heart, liver, eyes, vertebrae and the craniofacial region. Mutations in the JAG1 gene have been demonstrated to cause Alagille syndrome. JAG1 encodes a cellular membrane-bound ligand for the Notch receptor and is expressed during the normal development of tissues affected in Alagille syndrome. JAG1 mutations are detected in approximately 70% of AGS patients and are mostly protein truncating mutations. JAG1 mutations have also been described in patients that do not demonstrate the complete AGS phenotype, suggesting that the phenotypic spectrum of JAG1 mutations is broader than thus far assumed.

Bleeding tendency in children with Alagille syndrome.

OBJECTIVE: Spontaneous intracranial bleeding is now a widely recognized complication and cause of mortality in patients with Alagille syndrome. The pathogenesis of intracranial bleeding in these patients remains unclear. The aim of the study was to look for other sites of bleeding in these patients that could suggest a factor of multiorgan morbidity. METHODS: The records of 174 patients with Alagille syndrome were reviewed, and 38 (22%) patients without liver failure who experienced hemorrhage that led to a drop in hemoglobin level of at least 3 g/dL or to blood transfusion were identified. RESULTS: In 38 patients, 49 bleeding episodes occurred at a median age of 3.75 years (range: 1 month-27 years). Seventeen patients had 23 episodes of spontaneous bleeding; 21 patients bled during surgery or other medical procedures, and 5 among these 21 patients also had a spontaneous bleeding episode. Nine patients bled at least twice. Median platelets count and prothrombin time were normal. Severe cholestasis existed in 33 patients. One patient has a deletion of the 20p12 region, and 13 of 17 patients studied have a JAGGED1 mutation. Blood transfusion was necessary in 23 patients. Eight patients died secondary to bleeding (4 after surgery, 2 after gastrointestinal bleeding, 1 after needle liver biopsy, and 1 after intracranial bleeding). CONCLUSION: These results suggest that patients with Alagille syndrome are at special risk for bleeding; this should be taken into account before deciding on an invasive procedure. The mechanism of the bleeding is still unclear; the role of hypercholesterolemia cannot be excluded, but it may be speculated that JAGGED1 signaling abnormalities may impair the hemostatic function.

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.

Jagged1 (JAG1) mutation detection in an Australian Alagille syndrome population.

Alagille syndrome (AGS) is an autosomal dominant disorder characterized by abnormal development of the liver, heart, skeleton, eye, and face. Mutations in the Jagged1 gene (JAG1) have been found to result in the AGS phenotype and both protein truncating mutations and missense mutations have been identified. Using single stranded conformational polymorphism analysis we have screened 22 AGS affected individuals from 19 families for mutations within Jagged1. Twelve distinct Jagged1 mutations were identified in 15 (68.2%) of the 22 AGS cases, seven of which are novel. The mutations include three small deletions (25%), two small insertions (16.6%), three missense mutations (25%), two nonsense mutations (16.6%), and two splice-site mutations (16.6%). These mutations are spread across the entire coding sequence of the gene and most are localized to highly conserved motifs of the protein predicted to be important for Jagged1 function. One-half of the mutations found in this study are located between exons 9 and 12, a region constituting only 12% of the coding sequence. A splice-donor site mutation in intron 11 was shown to cause aberrant splicing of Jagged1 mRNA, consequently terminating translation prematurely in exon 12. The results of this study are consistent with the proposal that either haploinsufficiency for wild type Jagged1 and/or dominant negative effects produced by mutated Jagged1 are responsible for the AGS phenotype.