Alagille syndrome

Access and reattachment of biliary tree anomaly through Roux-en-Y hepaticojejunostomy: A case report

The right posterior segmental duct (RPSD) draining into the cystic duct is exceedingly rare. Ligation of the cystic duct in proximity to the junction of an aberrant right hepatic duct after a cholecystectomy can lead to life threatening complications. The present case study reveals a severed anomalous RPSD and subsequent Roux-en-Y hepaticojejunostomy procedure employed to fix biliary anomaly.

Intraretinal hemorrhages and detailed retinal phenotype of three patients with Alagille syndrome

PURPOSE

To explore patterns of disease expression in Alagille syndrome (ALGS).

METHODS

Patients underwent ophthalmic examination, optical coherence tomography (OCT) imaging, fundus intravenous fluorescein angiography (IVFA), perimetry and full-field electroretinograms (ffERGs). An adult ALGS patient had multimodal imaging and specialized perimetry.

RESULTS

The proband (P1) had a heterozygous pathogenic variant in JAG1; (p.Gln410Ter) and was incidentally diagnosed at age 7 with a superficial retinal hemorrhage, vascular tortuosity, and midperipheral pigmentary changes. The hemorrhage recurred 15 months later. Her monozygotic twin sister (P2) had a retinal hemorrhage at the same location at age 11. Visual acuities for both patients were 20/30 in each eye. IVFA was normal. OCT showed thinning of the outer nuclear in the peripapillary retina. A ffERG showed normal cone-mediated responses in P1 (rod-mediated ERGs not documented), normal ffERGs in P2. Coagulation and liver function were normal. An unrelated 42-year-old woman with a de-novo pathogenic variant (p. Gly386Arg) in JAG1 showed a similar pigmentary retinopathy and hepatic vascular anomalies; rod and cone function was normal across large expanses of structurally normal retina that sharply transitioned to a blind atrophic peripheral retina.

CONCLUSION

Nearly identical recurrent intraretinal hemorrhages in monozygotic twins with ALGS suggest a shared subclinical microvascular abnormality. We hypothesize that the presence of large areas of functionally and structurally intact retina surrounded by severe chorioretinal degeneration, is against a predominant involvement of JAG1 in the function of the neurosensory retina, and that instead, primary abnormalities of chorioretinal vascular development and/or homeostasis may drive the peculiar phenotypes.

Alagille-like syndrome with surprising karyotype: a case report

BACKGROUND

Chromosome 5p partial monosomy (5p-syndrome) and chromosome 6p partial trisomy are chromosomal abnormalities that result in a variety of symptoms, but liver dysfunction is not normally one of them. Alagille syndrome (OMIM #118450) is a multisystem disorder that is defined clinically by hepatic bile duct paucity and cholestasis, in association with cardiac, skeletal, and ophthalmologic manifestations, and characteristic facial features. Alagille syndrome is caused by mutations in JAG1 on chromosome 20 or NOTCH2 on chromosome 1. Here, we report a preterm infant with karyotype 46,XX,der(5)t(5,6)(p15.2;p22.3) and hepatic dysfunction, who was diagnosed as having incomplete Alagille syndrome.

CASE PRESENTATION

The Japanese infant was diagnosed based on the cardiac abnormalities, ocular abnormalities, characteristic facial features, and liver pathological findings. Analysis of the JAG1 and NOTCH sequences failed to detect any mutations in these genes.

CONCLUSIONS

These results suggest that, besides the genes that are known to be responsible for Alagille syndrome, other genetic mutations also may cause Alagille syndrome.

Alagille Syndrome: A Case Report

Alagille Syndrome (ALGS) is a rare, autosomal dominant inherited disorder that causes abnormalities of liver, eye, heart, skeleton and distinctive facial appearance. ALGS is caused by mutation in one of two genes: JAG1 and NOTCH2. There are some reports of Hearing Loss in patients with ALGS raising the possibility of involvement of both structural components of middle ear and sensorineural components of the inner ear. The present case study was to emphasize audiological perspectives of Alagille Syndrome in a nine year old female child. Audiologists must be well aware of the typical features and clinical perspectives of ALGS and should be an expert in selecting appropriate tests and in interpreting findings.

Outcomes of internal biliary diversion using cholecystocolostomy for patients with severe Alagille syndrome

Alagille syndrome (AGS) is a disorder that leads to increased serum cholesterol and bile acids, which can result in debilitating xanthomas and pruritus. External biliary drainage and transplantation are effective treatments for AGS. Internal biliary diversion with Roux-en-Y cholecystocolostomy has been described for other biliary conditions, but not AGS. Three patients with severe pruritus due to AGS underwent Roux-en-Y cholecystocolostomy for internal biliary drainage. Retrospective analysis compared preoperative and post-operative lab values and symptom scores (0, none–4, severe). Three patients underwent cholecystocolostomy. All patients had at least three diagnostic criteria for AGS. Mean preoperative pruritus score was 3.33 (range, 2–4) and mean post-operative score was 1. Mean preoperative xanthoma score was 1.33 (range, 0–4) and post-operative score was 1 at 2-month follow-up. Roux-en-Y cholecystocolostomy can be considered for AGS, which is refractory to medical management. This procedure accomplishes internal biliary diversion without significant physiologic derangements.

Broadening the clinical spectrum of ALGS: an Egyptian cohort with five novel mutations in JAG1 gene

Background

Alagille syndrome (ALGS) is a rare autosomal dominant multisystem disorder that affects the liver, heart, eyes, vertebrae, and kidneys and is associated with characteristic facies. This work aimed to study the spectrum of the clinical features of ALGS in an Egyptian cohort of patients in conjunction with partial sequencing of the JAG1 gene.

Methods

This study included 17 pediatric ALGS patients diagnosed on clinical grounds: facial features, cholestatic liver disease, and cardiac, vertebral, and ocular findings. Molecular analysis was conducted in 10 selected exons of the JAG1 gene.

Results

The clinical features of ALGS included cholestatic liver disease (100%), facial dysmorphism (100%), cardiac abnormalities (88.2%), butterfly vertebrae (64.7%), posterior embryotoxon (35.2%), poor growth (41%), xanthomata (11.8%), and hiatus hernia (11.8%). Five novel pathogenic JAG1 mutations were identified in this study, including two nonsense mutations, one splicing mutation, one frameshift insertion, and one frameshift deletion. In two patients, the mutations were confirmed to be de novo, as the mutations could not be detected in both parents.

Conclusion

Five novel JAG1 pathogenic variants were identified in this study. This is the first molecular study to report pathogenic mutations in the JAG1 gene within an Egyptian cohort of children with ALGS.

Two Novel Mutations in the JAG1 Gene in Pediatric Patients with Alagille Syndrome: The First Case Series in Czech Republic

Background: Alagille syndrome (ALGS) is a highly variable multisystem disorder inherited in an autosomal dominant pattern with incomplete penetration. The disorder is caused by mutations in the JAG1 gene, only rarely in the NOTCH2 gene, which gives rise to malformations in multiple organs. Bile duct paucity is the main characteristic feature of the disease. Methods: Molecular-genetic examination of genes JAG1 and NOTCH2 in four probands of Czech origin who complied with the diagnostic criteria of ALGS was performed using targeted next-generation sequencing of genes JAG1 and NOTCH2. Segregation of variants in a family was assessed by Sanger sequencing of parental DNA. Results: Mutations in the JAG1 gene were confirmed in all four probands. We identified two novel mutations: c.3189dupG and c.1913delG. Only in one case, the identified JAG1 mutation was de novo. None of the parents carrying JAG1 pathogenic mutation was diagnosed with ALGS. Conclusion: Diagnosis of the ALGS is complicated due to the absence of clear genotype-phenotype correlations and the extreme phenotypic variability in the patients even within the same family. This fact is of particular importance in connection to genetic counselling and prenatal genetic testing.

Pseudotumor cerebri syndrome in a child with Alagille syndrome: intracranial pressure dynamics and treatment outcome after ventriculoperitoneal shunting

Alagille syndrome (AS) is a rare multisystem disease of the liver, heart, eyes, face, skeleton, kidneys, and vascular system. The occurrence of pseudotumor cerebri syndrome (PTCS) in patients with AS has been reported only exceptionally. Owning to its rarity and a mostly atypical presentation, the diagnosis and natural history of affected patients remain uncertain. We report an atypical case of PTCS in a 4-year-old boy with a known history of AS who presented with bilateral papilledema (PE) on a routine ophthalmological examination. Visual findings deteriorated after treatment with acetazolamide. Continuous intracranial pressure (ICP) monitoring was then utilized to investigate ICP dynamics. Successful treatment with resolution of PE was achieved after ventriculoperitoneal shunting but relapsed due to growth-related dislocation of the ventricular catheter. This report brings new insights into the ICP dynamics and the resulting treatment in this possibly underdiagnosed subgroup of PTCS patients. It also demonstrates that ventriculoperitoneal shunting can provide long-term improvement of symptoms for more than 10 years.

Transcriptome Analysis Reveals High Similarities between Adult Human Cardiac Stem Cells and Neural Crest-Derived Stem Cells

For the identification of a stem cell population, the comparison of transcriptome data enables the simultaneous analysis of tens of thousands of molecular markers and thus enables the precise distinction of even closely related populations. Here, we utilized global gene expression profiling to compare two adult human stem cell populations, namely neural crest-derived inferior turbinate stem cells (ITSCs) of the nasal cavity and human cardiac stem cells (hCSCs) from the heart auricle. We detected high similarities between the transcriptomes of both stem cell populations, particularly including a range of neural crest-associated genes. However, global gene expression likewise reflected differences between the stem cell populations with regard to their niches of origin. In a broader analysis, we further identified clear similarities between ITSCs, hCSCs and other adherent stem cell populations compared to non-adherent hematopoietic progenitor cells. In summary, our observations reveal high similarities between adult human cardiac stem cells and neural crest-derived stem cells from the nasal cavity, which include a shared relation to the neural crest. The analyses provided here may help to understand underlying molecular regulators determining differences between adult human stem cell populations.

Notch signaling: Its essential roles in bone and craniofacial development

Notch is a cell–cell signaling pathway that is involved in a host of activities including development, oncogenesis, skeletal homeostasis, and much more. More specifically, recent research has demonstrated the importance of Notch signaling in osteogenic differentiation, bone healing, and in the development of the skeleton. The craniofacial skeleton is complex and understanding its development has remained an important focus in biology. In this review we briefly summarize what recent research has revealed about Notch signaling and the current understanding of how the skeleton, skull, and face develop. We then discuss the crucial role that Notch plays in both craniofacial development and the skeletal system, and what importance it may play in the future.

Notch Dosage: Jagged1 Haploinsufficiency Is Associated With Reduced Neuronal Division and Disruption of Periglomerular Interneurons in Mice

Neural stem cells in the lateral ganglionic eminence (LGE) generate progenitors that migrate through the rostral migratory stream (RMS) to repopulate olfactory bulb (OB) interneurons, but the regulation of this process is poorly defined. The evolutionarily conserved Notch pathway is essential for neural development and maintenance of neural stem cells. Jagged1, a Notch ligand, is required for stem cell maintenance. In humans, heterozygous mutations in JAGGED1 cause Alagille syndrome, a genetic disorder characterized by complications such as cognitive impairment and reduced number of bile ducts in the liver, suggesting the presence of a JAGGED1 haploinsufficient phenotype. Here, we examine the role of Jagged1 using a conditional loss-of-function allele in the nervous system. We show that heterozygous Jagged1 mice possess a haploinsufficient phenotype that is associated with a reduction in size of the LGE, a reduced proliferative state, and fewer progenitor cells in the LGE and RMS. Moreover, loss of Jagged1 leads to deficits in periglomerular interneurons in the OB. Our results support a dose-dependent role for Jagged1 in maintaining progenitor division within the LGE and RMS.

Outcomes of Childhood Cholestasis in Alagille Syndrome: Results of a Multicenter Observational Study

Alagille syndrome (ALGS) is an autosomal dominant multisystem disorder with cholestasis as a defining clinical feature. We sought to characterize hepatic outcomes in a molecularly defined cohort of children with ALGS‐related cholestasis. Two hundred and ninety‐three participants with ALGS with native liver were enrolled. Participants entered the study at different ages and data were collected retrospectively prior to enrollment, and prospectively during the study course. Genetic analysis in 206 revealed JAGGED1 mutations in 91% and NOTCH2 mutations in 4%. Growth was impaired with mean height and weight z‐scores of <−1.0 at all ages. Regression analysis revealed that every 10 mg/dL increase in total bilirubin was associated with a decrease in height z‐score by 0.10 (P = 0.03) and weight z‐score by 0.15 (P = 0.007). Total bilirubin was higher for younger participants (P = 0.03) with a median of 6.9 mg/dL for those less than 1 year old compared with a median of 1.3 mg/dL for participants 13 years or older. The median gamma glutamyl transferase also dropped from 612 to 268 in the same age groups. After adjusting for age, there was substantial within‐individual variation of alanine aminotransferase. By 20 years of age, 40% of participants had developed definite portal hypertension. Estimated liver transplant–free survival at the age of 18.5 years was 24%. Conclusions: This is the largest multicenter natural history study of cholestasis in ALGS, demonstrating a previously underappreciated burden of liver disease with early profound cholestasis, a second wave of portal hypertension later in childhood, and less than 25% of patients reaching young adulthood with their native liver. These findings will promote optimization of ALGS management and development of clinically relevant endpoints for future therapeutic trials.

Capillary Malformation-Arteriovenous Malformation Combined Alagille Syndrome in a Patient With Double Gene Variations of RASA1 and NOTCH2

Background: Capillary malformation–arteriovenous malformation (CM-AVM) is an autosomal dominant disorder characterized by CMs, often in association with fast-flow vascular malformations. Alagille syndrome is an autosomal dominant multisystem disorder, usually involving hepatic, cardiac, ophthalmic, skeletal, or renal dysplasia. The combination of CM-AVM and Alagille syndrome in a patient presenting serious vascular malformations in the liver and heart has never been reported. Here, we report the case of a 20-month-old infant presenting these two diseases.

Case presentation: The patient manifested port-wine stains, congenital heart disease, cholestasis with abnormal morphology, and vascular anomalies. Color Doppler (B-mode) ultrasonography, and radiological imaging including computed tomography (CT) with enhanced three-dimensional (3D) reconstruction and angiography, revealed a type II Abernethy malformation in the hepatic portal vein. The left hepatic lobe was enlarged showing dilation of the portal vein and the left artery. Whole exome sequencing (WES) identified a paternally inherited RASA1 heterozygous pathogenic variant p.(Ser219Ter) causing CM-AVM and a de novo NOTCH2 heterozygous variant p.(Met2042Thr) associated with Alagille syndrome.

Conclusion: This is the first case of combined CM-AVM and Alagille syndrome presenting serious liver and heart abnormalities diagnosed using imaging technology and WES. The patient harbored variants in two genes: RASA1 and NOTCH2, which rarely contribute to aberrant vascular development. This report highlights the value of accurately diagnosing similar diseases and guiding therapy using genetic testing combined with careful clinical examinations.

Cholestasis in the Baby and Infant

Cholestasis in children is a serious condition due to various aetiologic factors. If children with jaundice present with acholic stool, dark urine colour, or direct hyperbilirubinaemia, the patient should be evaluated urgently. Early and timely diagnosis and initiation of appropriate treatment are extremely important determinants of morbidity and mortality. In the neonatal period, idiopathic neonatal cholestasis, alpha-1 antitrypsin deficiency, cholestasis from infections, and biliary atresia are the most common causes of cholestasis. Nowadays, with the development of genetic and molecular biological studies, the diagnosis of many diseases that have previously been evaluated as ‘idiopathic‘ can be made. It is the aetiological factor that determines the prognosis. The treatment plan is created in accordance with aetiological causes and in response to symptoms such as pruritus and malabsorption: this can be surgical treatment across a diverse spectrum, from biliary diversion to liver transplantation. In this study, the aetiology, diagnosis, and treatment of cholestasis in babies and infants are reviewed in the light of current literature.

Jagged1 is Essential for Radial Glial Maintenance in the Cortical Proliferative Zone

Radial glial maintenance is essential for the proper development of the cortex. It is known that the evolutionarily conserved Notch signaling pathway is required for maintaining the pool of radial glial stem cells although the mechanisms involved are not entirely understood. Here, we study the Notch ligand, Jagged1, in the mouse ventricular zone at a late stage of embryonic development. We use a conditional loss of function allele to show that Jagged1 is required for maintaining radial glial cells and when absent, leads to defects in the cortical proliferation zone and expression of intermediate progenitor cells. Using in vitro approaches, we found that depletion of Jagged1 reduced the size of primary neurospheres and their capacity to self-renewal. Finally, Jagged1 mutants also showed precocious neuronal differentiation and cortical defects. Together, these data support a role for Jagged1 in radial glia maintenance in the neocortex.

Persistent cholestasis resulting from duodenal papillary carcinoma in an adolescent male: A case report

RATIONALE

Cholestasis in pediatric patients has diverse etiologies and can be broadly classified as intrahepatic or extrahepatic. The common causes of extrahepatic cholestasis are bile duct calculus, inflammation, or pancreatitis. Malignant tumor is a rare cause of bile ducts obstruction in adolescent. Here we report a 14-year-old male patient with cholestasis due to poorly differentiated adenocarcinoma.

PATIENT CONCERNS

A 14-year-old male patient with cholestasis was admitted because of jaundice, weakness, weight loss, and stomach pain for 2 months. The patient had been diagnosed with epilepsy 4 years previously and was being treated with sodium valproate and oxcarbazepine. On admission, laboratory studies showed elevated levels of aspartate aminotransferase (271 IU/L), alanine aminotransferase (224 IU/l), γ-glutamyltransferase (1668.9 IU/L), total bilirubin (66.4 μmol/L), and direct bilirubin (52.6 μmol/L). Additional laboratory tests eliminated common causes of cholestasis such as bacterial/viral infection, autoimmune liver disease, Wilson disease, Alagille syndrome, or progressive familial intrahepatic cholestasis type 3. The results of laboratory investigations showed no improvement after 10 days of treatment with ursodeoxycholic acid and vitamins A, D, and K1. Enhanced magnetic resonance imaging demonstrated a tumor of 22 mm diameter in the duodenal lumen and dilatation of the common bile duct. Endoscopic retrograde cholangiopancreatography detected a tumor in the duodenal lumen.

DIAGNOSIS

Considering the clinical features, imaging manifestation, endoscopic findings, and pathologic characteristic, the patient was diagnosed with poorly differentiated adenocarcinoma.

INTERVENTIONS

The patient underwent pancreaticoduodenectomy and chemotherapy.

OUTCOME

The patient recovered well. Elevated levels of tumor biomarkers or abnormal liver function tests have not occurred during the 2-year follow-up.

CONCLUSION

Cholestasis resulting from primary duodenal papillary carcinoma is rare in pediatric patients but should be considered in the differential diagnosis.

Alagille Syndrome and the Liver: Current Insights

Alagille syndrome (ALGS) is an autosomal dominant disorder, with multisystem involvement, which usually occurs due to Notch signaling pathway defects, mostly due to JAG1 mutation (ALGS type 1), but rarely due to neurogenic locus notch homolog protein (NOTCH2) mutation (ALGS type 2). It was suspected in cases having at least three out of five major clinical criteria: cholestasis with a paucity of the bile duct, congenital cardiac defects, ocular posterior embryotoxon, typical facial features, and skeletal malformation. Till date, no early predictive marker for hepatic outcome in ALGS has found. No genotypic or, phenotype features or correlation could predict the development of endstage liver disease, which poses a unique management challenge. Cases with progressive liver damage, unremitting cholestasis and intractable pruritus often depend on liver transplantation as last resort. The cardiac, and renal status should be well accessed before liver transplant for the better post-transplantation outcome. Most of the clinical manifestations usually improve the following transplant, except any change in stature. The post liver transplantation outcome was usually comparable with other conditions which require liver transplantation as a last resort, but in this disease the effect of long term immunosuppression on other affected systems not evaluated well till date. Therefore long term post transplant prospective study is required to address these issues.

How to cite this article: Singh SP, Pati GK. Alagille Syndrome and the Liver: Current Insights. Euroasian J Hepatogastroenterol, 2018;8(2):140-147

Hepatocellular carcinoma in non-cirrhotic liver: A comprehensive review

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer, which in turns accounts for the sixth most common cancer worldwide. Despite being the 6^th most common cancer it is the second leading cause of cancer related deaths. HCC typically arises in the background of cirrhosis, however, about 20% of cases can develop in a non-cirrhotic liver. This particular subgroup of HCC generally presents at an advanced stage as surveillance is not performed in a non-cirrhotic liver. HCC in non-cirrhotic patients is clinically silent in its early stages because of lack of symptoms and surveillance imaging; and higher hepatic reserve in this population. Interestingly, F3 fibrosis in non-alcoholic fatty liver disease, hepatitis B virus and hepatitis C virus infections are associated with high risk of developing HCC. Even though considerable progress has been made in the management of this entity, there is a dire need for implementation of surveillance strategies in the patient population at risk, to decrease the disease burden at presentation and improve the prognosis of these patients. This comprehensive review details the epidemiology, risk factors, clinical features, diagnosis and management of HCC in non-cirrhotic patients and provides future directions for research.

Alagille Syndrome: A Novel Mutation in JAG1 Gene

Alagille syndrome is an autosomal dominant multisystem disorder with variable phenotypic penetrance, caused by heterozygous mutations in JAG1 or NOTCH2, encoding for the components of the Notch signaling pathway. In this paper, we described a novel mutation not yet reported in literature. This 3-years old male child was referred to our Clinical Genetics Unit because of delayed psychomotor development, systolic murmur, dysmorphic facial features, and hypertransaminasemia. The novel JAG1 heterozygous c.2026delT variant in exon 16 was found. JAG1 mutations are classified as protein truncating and non-protein truncating, without any genotype-phenotype correlation. The detected mutation determines a stop codon (p.Cys676AlafsTer67) in the gene sequence, encoding a truncated protein. Our report broadens the spectrum of JAG1 gene mutations.

Alagille Syndrome

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.

Nodular macroregenerative tissue as a pattern of regeneration in cholangiopathic disorders

BACKGROUND

Published case series have described central hepatic macroregenerative nodules or masses as a common feature of Alagille syndrome. Our experience suggests this regenerative pattern can be seen more generally in cholangiopathic disorders.

OBJECTIVE

To define the frequency of central regenerative tissue in Alagille syndrome and other cholangiopathic disorders and to describe the typical appearance of such regenerative tissue.

MATERIALS AND METHODS

We conducted a retrospective study of CT and MR imaging performed in children and young adults with cholangiopathic disorders between January 2000 and June 2016. Two pediatric radiologists reviewed images in consensus for the presence and features of macroregenerative tissue. Tissue histopathology, when available, was retrieved from the medical record.

RESULTS

Of 226 patients with cholangiopathic disorders, 23% (52/226) had macroregenerative tissue, and this tissue was central in 96% (50/52). Tissue was well defined and mass-like in 38% (20/52). Regenerative tissue was most common among the subset of patients with Langerhans cell histiocytosis with hepatic involvement (71%, 5/7) and was identified in 43% (16/37) of patients with Alagille syndrome. Regenerative tissue was iso- to hyperintense on T1-weighted MR sequences in 96% (50/52) of cases and hypointense on T2-weighted MR imaging in 94% (48/51). Arterial phase hyperenhancement was present in only five patients (12% of 43), none of whom showed portal venous phase washout. Histopathology was available for 20 cases, all showing benign regenerative tissue.

CONCLUSION

Central mass-like regeneration appears to be a common regenerative pattern in cholangiopathic disorders and should not be mistaken for malignancy.

Computational simulation of postoperative pulmonary flow distribution in Alagille patients with peripheral pulmonary artery stenosis

BACKGROUND

Up to 90% of individuals with Alagille syndrome have congenital heart diseases. Peripheral pulmonary artery stenosis (PPS), resulting in right ventricular hypertension and pulmonary flow disparity, is one of the most common abnormalities, yet the hemodynamic effects are ill-defined, and optimal patient management and treatment strategies are not well established. The purpose of this pilot study is to use recently refined computational simulation in the setting of multiple surgical strategies, to examine the influence of pulmonary artery reconstruction on hemodynamics in this population.

MATERIALS AND METHODS

Based on computed tomography angiography and cardiac catheterization data, preoperative pulmonary artery models were constructed for 4 patients with Alagille syndrome with PPS (all male, age range: 0.6-2.9 years), and flow simulations with deformable walls were performed. Surgeon directed virtual surgery, mimicking the surgical procedure, was then performed to derive postoperative models. Postoperative simulation-derived hemodynamics and blood flow distribution were then compared with the clinical results.

RESULTS

Simulations confirmed substantial resistance, resulting from preoperative severe ostial stenoses, and the use of newly developed adaptive outflow boundary conditions led to excellent agreement with in vivo measurements. Relief of PPS decreased pulmonary artery pressures and improved pulmonary flow distribution both in vivo and in silico with good correlation.

CONCLUSIONS

Using adaptive outflow boundary conditions, computational simulations can estimate postoperative overall pulmonary flow distribution in patients with Alagille syndrome after pulmonary artery reconstruction. Obstruction relief along with pulmonary artery vasodilation determines postoperative pulmonary flow distribution and newer methods can incorporate these physiologic changes. Evolving blood flow simulations may be useful in surgical or transcatheter planning and in understanding the complex interplay among various obstructions in patients with peripheral pulmonary stenosis.

Perioperative Anesthetic Management of Patients Having Liver Transplantation for Uncommon Conditions

This review focuses on the perioperative anesthetic management of patients having liver transplantation (LT) performed for several uncommon indications or in combination with rare pathology. Conditions discussed in the article include Alagille syndrome, hypertrophic cardiomyopathy, Gilbert's syndrome, porphyria, Wilson's disease, and Budd-Chiari syndrome. In comparison to other indications, LT in these settings is infrequent because of the low incidence of these pathologies. Most of these conditions (with the exception of Gilbert syndrome) are associated with a high probability of significant perioperative complications and increased mortality and morbidity. Experience in management of these unusual conditions is only gained over time. Developing clinical pathways for patients with these conditions should result in outcomes similar to LT performed for more common indications.

Alagille syndrome: Genetics and Functional Models

Purpose of review

We review the genetics of the autosomal dominant, multi-system disorder, Alagille syndrome and provide a summary on how current functional models and emerging biotechnologies are equipped to guide scientists towards novel therapies. The importance of haploinsufficiency as a disease mechanism will be underscored throughout this discussion.

Recent findings

Alagille syndrome, a human disorder affecting the liver, heart, vasculature, kidney, and other systems, is caused by mutations in the Notch signaling pathway ligand, Jagged1 (JAG1) or the receptor, NOTCH2. Current advances in animal modeling, in vitro cell culture, and human induced pluripotent stem cells, provide new opportunities in which to study disease mechanisms and manifestations.

Summary

We anticipate that the availability of innovative functional models will allow scientists to test new gene therapies or small molecule treatments in physiologically-relevant systems. With these advances, we look forward to the development of new methods to help Alagille syndrome patients.

Requirement for Jagged1-Notch2 signaling in patterning the bones of the mouse and human middle ear

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.

A Newborn with Panhypopituitarism and Seizures

Interstitial deletions on the short arm of chromosome 20 are uncommon, and therefore the clinical phenotype is poorly defined. Very few cases have been reported in the literature so far. In this report, we describe a 4-month-old female with a heterozygous deletion at 20p11.21p12.1 with panhypopituitarism and cardiac, gastrointestinal, and genitourinary anomalies along with dysmorphic facial features. We compared and discussed similar cases with overlapping deletions in 20p11 region. We wish to report this rare occurrence as this may better define the phenotypes of the 20p interstitial deletion with certain dysmorphic features, multiorgan involvement, and related clinical characteristics in this patient population.

MiR-199b-5p inhibits osteogenic differentiation in ligamentum flavum cells by targeting JAG1 and modulating the Notch signalling pathway

Ossification of the ligamentum flavum (OLF) is a pathology almost only reported in East Asian countries. The leading cause of OLF is thoracic spinal canal stenosis and myelopathy. In this study, the role of miR-199b-5p and jagged 1 (JAG1) in primary ligamentum flavum cell osteogenesis was examined. MiR-199b-5p was found to be down-regulated during osteogenic differentiation in ligamentum flavum cells, while miR-199b-5p overexpression inhibited osteogenic differentiation. In addition, JAG1 was found to be up-regulated during osteogenic differentiation in ligamentum flavum cells, while JAG1 knockdown via RNA interference caused an inhibition of Notch signalling and osteogenic differentiation. Moreover, target prediction analysis and dual luciferase reporter assays supported the notion that JAG1 was a direct target of miR-199b-5p, with miR-199b-5p found to down-regulate both JAG1 and Notch. Further, JAG1 knockdown was demonstrated to block the effect of miR-199b-5p inhibition. These findings imply that miR-199b-5p performs an inhibitory role in osteogenic differentiation in ligamentum flavum cells by potentially targeting JAG1 and influencing the Notch signalling pathway.

Notch Signaling and the Skeleton

Notch 1 to 4 receptors are important determinants of cell fate and function, and Notch signaling plays an important role in skeletal development and bone remodeling. After direct interactions with ligands of the Jagged and Delta-like families, a series of cleavages release the Notch intracellular domain (NICD), which translocates to the nucleus where it induces transcription of Notch target genes. Classic gene targets of Notch are hairy and enhancer of split (Hes) and Hes-related with YRPW motif (Hey). In cells of the osteoblastic lineage, Notch activation inhibits cell differentiation and causes cancellous bone osteopenia because of impaired bone formation. In osteocytes, Notch1 has distinct effects that result in an inhibition of bone resorption secondary to an induction of osteoprotegerin and suppression of sclerostin with a consequent enhancement of Wnt signaling. Notch1 inhibits, whereas Notch2 enhances, osteoclastogenesis and bone resorption. Congenital disorders of loss- and gain-of-Notch function present with severe clinical manifestations, often affecting the skeleton. Enhanced Notch signaling is associated with osteosarcoma, and Notch can influence the invasive potential of carcinoma of the breast and prostate. Notch signaling can be controlled by the use of inhibitors of Notch activation, small peptides that interfere with the formation of a transcriptional complex, or antibodies to the extracellular domain of specific Notch receptors or to Notch ligands. In conclusion, Notch plays a critical role in skeletal development and homeostasis, and serious skeletal disorders can be attributed to alterations in Notch signaling.

Adaptive outflow boundary conditions improve post-operative predictions after repair of peripheral pulmonary artery stenosis

Peripheral pulmonary artery stenosis (PPS) is a congenital abnormality resulting in pulmonary blood flow disparity and right ventricular hypertension. Despite recent advance in catheter-based interventions, surgical reconstruction is still preferred to treat complex PPS. However optimal surgical strategies remain unclear. It would be of great benefit to be able to predict post-operative hemodynamics to assist with surgical planning toward optimizing outcomes. While image-based computational fluid dynamics has been used in cardiovascular surgical planning, most studies have focused on the impact of local geometric changes on hemodynamic performance. Previous experimental studies suggest morphological changes in the pulmonary arteries not only alter local hemodynamics but also lead to distal pulmonary adaptation. In this proof of concept study, a constant shear stress hypothesis and structured pulmonary trees are used to derive adaptive outflow boundary conditions for post-operative simulations. Patient-specific simulations showed the adaptive outflow boundary conditions by the constant shear stress model to provide better predictions of pulmonary flow distribution than the conventional strategy of maintaining outflow boundary conditions. On average, the relative difference, when compared to the gold standard clinical test, in blood flow distribution to the right lung is reduced from 20 to 4 %. This suggests adaptive outflow boundary conditions should be incorporated into post-operative modeling in patients with complex PPS.

Solitary Hepatic Nodule Adjacent to the Right Portal Vein: A Common Finding of Alagille Syndrome?

BACKGROUND

Hepatic lesions have been described in Alagille syndrome (ALGS) in isolated case reports, and most of these have been reported to be hepatocellular carcinoma.

OBJECTIVES

The aim of the present study was to determine the frequency, imaging, and histopathologic characteristics of hepatic lesions in children with ALGS.

METHODS

Available abdominal imaging of children with ALGS was retrospectively reviewed to note the presence of any focal liver lesion, its location, and imaging characteristics. Other findings including signs of portal hypertension, portal lymph nodes, and splenic and renal abnormalities were also noted. Findings were correlated with pathology in available cases and with clinical follow-up.

RESULTS

Of 55 children with clinically and/or genetically confirmed ALGS followed in the liver clinic, 39 (19 boys, 20 girls; mean age 8.9 years) with imaging available on picture archival and communication system were included in the study. Focal hepatic lesions were seen in 12 of the 39 (30%) children, solitary in 11 and multiple in 1. Ten of these children had a large nodule adjacent to the right portal vein. The median diameter of the lesions was 8.1 cm (range 5.6-9.8 cm). Magnetic resonance imaging features and pathology in available cases were suggestive of a regenerative nodule. α-fetoprotein levels were normal in all except 1 child who had mild elevation.

CONCLUSIONS

Combining our series and previous case reports, the presence of a large nodule adjacent to the right portal vein appears to be a common finding in ALGS. The typical location, normal α-fetoprotein levels, and magnetic resonance imaging features with vessels coursing through the lesion can reliably differentiate this benign nodule from hepatocellular carcinoma.

Human pancreas development

A wealth of data and comprehensive reviews exist on pancreas development in mammals, primarily mice, and other vertebrates. By contrast, human pancreatic development has been less comprehensively reviewed. Here, we draw together those studies conducted directly in human embryonic and fetal tissue to provide an overview of what is known about human pancreatic development. We discuss the relevance of this work to manufacturing insulin-secreting β-cells from pluripotent stem cells and to different aspects of diabetes, especially permanent neonatal diabetes, and its underlying causes.

Jagged1 (JAG1): Structure, expression, and disease associations

Jagged1 (JAG1) is one of the 5 cell surface ligands that functions primarily in the highly conserved Notch signaling pathway. Notch signaling plays a critical role in cellular fate determination and is active throughout development and across many organ systems. The classic JAG1-NOTCH interaction leads to a cascade of proteolytic cleavages resulting in the NOTCH intracellular domain being transported into the nucleus where it functions to activate downstream transcription of target genes. JAG1 mutations have been associated with several disorders including the multi-system dominant disorder Alagille syndrome, and some cases of tetralogy of Fallot (although these may represent variable expressivity of Alagille syndrome). In addition, variations in JAG1 have been found to be associated with multiple types of cancer including breast cancer and adrenocortical carcinoma. Alagille syndrome, which primarily affects the liver, heart, skeleton, eye, face, kidney and vasculature is caused by loss of function mutations in JAG1, demonstrating that haploinsufficiency for JAG1 is disease causing, at least in these tissues. Expression and conditional gene knockout studies of JAG1 (Jag1) have correlated with tissue-specific disease phenotypes and have provided insight into both disease pathogenesis and human development.

Subarachnoid hemorrhage due to aneurysm rupture in a young woman with Alagille syndrome - A rare cause of sudden death

The Alagille syndrome (AGS) or arteriohepatic dysplasia is a rare, autosomal dominant inherited disease with a prevalence of approximately 1:100,000. AGS was first described in 1969 and affects liver, heart, arterial blood vessels, skeleton and the eyes. The expression of AGS is variable. In severe cases a liver transplantation is required. Presented is the case of a 25-year-old woman with AGS. At the age of 7 and 8years she had liver transplantations. Other typical findings associated with Alagille syndrome (e.g. pulmonary or renal anomalies) were also present. The young woman apparently died suddenly and unexpectedly in a good health condition despite regular medical treatment. Cause of death was a subarachnoid hemorrhage with invasion of the hemorrhage into the ventricle system caused by a rupture of previously unknown large aneurysm in the terminal basilary artery. Intracranial vascular malformations are a common finding in patients with AGS and cause death in up to 16% of them. Life expectancy in AGS patients depends on the severity of changes of the affected liver. But AGS is also responsible for various vascular abnormalities in several other organs which can cause lethal complications. Due to the high rate of vascular complications and intracranial hemorrhage with the leading cause of mortality in patients with AGS, vascular screening by the use of noninvasive imaging techniques (CT or MR angiography) is required to avoid unexpected sudden death.

Computed tomography and magnetic resonance imaging in neonates with congenital cardiovascular disease

Most cardiac diseases in the newborn are caused by structural abnormalities developed in utero. With few exceptions, palliative and definitive treatments require cardiac surgery. The diagnosis and management decisions regarding uncomplicated lesions, such as atrial septal defect, ventricular septal defect, patent ductus arteriosus, and tetralogy of Fallot, can be accomplished by echocardiography alone. Abnormalities beyond the sonographic window, complex 3-dimensional lesions, and detailed functional information require additional imaging. In the past, this was fulfilled by catheter angiography, but today much of the information can be obtained from noninvasive computed tomography angiography and magnetic resonance imaging. This article discusses the design and application of these imaging techniques to the newborn, with emphasis on safety, efficacy, and image quality. Understanding the capabilities and limitations of these techniques is crucial for making rational choices among imaging options based on sound risk and benefit considerations. Important examples of congenital heart lesions have been illustrated with 3-dimensional reconstruction from computed tomography and magnetic resonance images.

Characteristics and outcome of liver transplantation in children with Alagille syndrome: a single-center experience

BACKGROUND

This study was carried out in Chang Gung Memorial Hospital-Kaohsiung Medical Center, Taiwan, with the aim of reviewing the characteristics and the outcome of liver transplantation (LT) in children with Alagille syndrome (AGS).

METHODS

We performed a retrospective analysis of transplant records of children diagnosed with AGS and undergoing LT between 1987 and 2010.

RESULTS

Nine patients underwent living donor LT. Cholestasis and characteristic facies were seen in all patients. Posterior embryotoxon was seen in 4/9 (44.4%), butterfly vertebrae in 3/9 (33.3%), heart defect (pulmonary stenosis in 2) in 3/9 (33.3%), and renal disease in 2/9 (22.2%) patients. Five cases had cholestasis prior to the age of 60 days, whereas four cases had cholestasis after 60 days of age. Iminodiacetic acid scans showed no excretion of isotope into the bowel in four cases and suggested a false diagnosis of biliary atresia. All patients underwent diagnostic laparotomy and liver biopsy. Results of liver biopsy showed characteristic features of paucity of interlobular bile ducts in all patients. Kasai portoenterostomy was not performed in any patient prior to being referred for LT. The mean age at the time of LT was 4.6 years. The 5-year overall survival rate after living donor LT was 88.9%.

CONCLUSION

Our conclusion is that the clinical features of AGS are informative. In addition, histological confirmation is important in the diagnosis. AGS children with severe liver disease had good prognoses with LT.

Medical and dental management of Alagille syndrome: a review

Alagille syndrome is a rare, autosomal, complex, dominant disorder associated with dysfunction of the liver, heart, skeleton, and eyes, as well as characteristic facial appearance. It is associated with the defect in component of the Notch signalling pathway. Here, we review the main features of Alagille syndrome with special focus on oro-facial manifestations like prominent forehead, moderate hypertelorism with deep-set eyes, a saddle or straight nose with a flattened, bulbous tip, and large ears. The article is based on the most recent and significant literature available from the Medline database.

Contrary to healthy children, patients with Alagille syndrome have many problems, depending on several factors like the severity of cholestasis and scarring in the liver, heart or lung problems, presence of infections, or other problems related to poor nutrition that can manifest in their oral cavity in the dental and periodontal tissues, as well as oral mucosa. From the dentist’s view, the most important elements are careful observation, accurate diagnosis, and planned management of such patients, especially during the patient’s formative years, to prevent complications. Aggressive preventive oral care and consultations with medical specialists before any invasive procedure are obligatory. All this can improve quality of life in patients with Alagille syndrome.

Polymorphism analysis and new JAG1 gene mutations of Alagille syndrome in Mexican population

Alagille syndrome is a multisystem disorder with an autosomic dominant pattern of inheritance that affects the liver, heart, eyes, kidneys, skeletal system and presents characteristic facial features. Mutations of the JAG1 gene have been identified in 20–89% of the patients with Alagille syndrome, this gene encodes for a ligand that activates the Notch signaling pathway. In the present study we analyzed 9 Mexican patients with Alagille syndrome who presented the clinical criteria for the classical presentation of the disease. By using the denaturing high performance liquid chromatography mutation analysis we were able to identify different mutations in 7 of the patients (77.77%), importantly, we found 5 novel mutations in JAG1 gene. The allelic frequency distribution of 13 polymorphisms in Mexican population is also reported. The overall results demonstrated an expanding mutational spectrum of JAG1 gene in the Mexican population.

Phenobarbital-enhanced hepatobiliary scintigraphy in the diagnosis of biliary atresia: two decades of experience at a tertiary center

BACKGROUND

Hepatobiliary scintigraphy is highly sensitive for diagnosing biliary atresia; however, its specificity has varied in the literature from 35% to 97%.

OBJECTIVE

The purpose of this study was to re-evaluate the accuracy of phenobarbital-enhanced hepatobiliary scintigraphy in differentiating biliary atresia from other causes of neonatal cholestasis.

MATERIALS AND METHODS

We retrospectively reviewed all hepatobiliary scans of infants with cholestasis at our institution from December 1990 to May 2011. Per our routine protocol the scans were obtained after pretreatment with phenobarbital (5 mg/kg/day for 5 days) to achieve a serum level of ≥15 mcg/ml. Normal hepatic uptake with no biliary excretion by 24 h was considered consistent with biliary atresia.

RESULTS

One hundred eighty-six infants with 210 hepatobiliary scans composed the study group. Forty-three (23%) infants had the final diagnosis of biliary atresia. Hepatobiliary scintigraphy was 100% sensitive, 93% specific and 94.6% accurate in diagnosing biliary atresia. Of the 186, 39/111 (35.1%) term and 2/68 (2.9%) preterm infants had biliary atresia; two of seven children with unknown gestational age also had biliary atresia. Other diagnoses included neonatal hepatitis, total parenteral nutrition cholestasis, Alagille syndrome, cystic fibrosis, choledochal cyst, hypothyroidism, alpha-1 antitrypsin deficiency and persistent cholestasis of unknown etiology.

CONCLUSION

Phenobarbital-enhanced hepatobiliary scintigraphy is highly accurate in differentiating biliary atresia from other causes of neonatal cholestasis. Biliary atresia is rare in premature infants.

Notch signaling and bone remodeling

Notch signaling plays context-dependent roles in the development and maintenance of many cell types and tissues in mammals. In the skeleton, both osteoblasts and osteoclasts require Notch signaling for proper differentiation and function, and the specific roles of Notch are dependent on the differentiation status of the cell. The recent discovery of activating NOTCH2 mutations as the cause of Hajdu-Cheney syndrome has highlighted the significance of Notch signaling in human bone physiology.

In vitro analysis of bone phenotypes in Col1a1 and Jagged1 mutant mice using a standardized osteoblast cell culture system

The mouse is a valuable model organism for studying bone biology and for unravelling pathological processes in skeletal disorders. In vivo methods like X-ray analysis, DXA measurements, pQCT and μCT are available to investigate the bone phenotype of mutant mice. However, the descriptive nature of such methods does not provide insights into the cellular and molecular bases of the observed bone alterations. Thus, first-line investigations might be complemented by cell culture-based methods to characterize the pathological processes at the cellular level independent from systemic influences. By combining well-established assays, we designed a comprehensive test system to investigate the cellular and molecular phenotype of primary calvarial osteoblasts in mutant mice compared to wild-type controls as a first-line phenotyping method. The compilation of 9 different quantifiable assays allows assessment of general properties of cell growth and investigation of bone-specific parameters at the functional, protein and RNA level in a kinetic fashion throughout a 3-week culture period, thus maximizing the chance to discover and explain new phenotypes in mutant mice. By analyzing mutant mouse lines for Col1a1 and Jag1 (Delta-Notch pathway) that both showed clear alterations in several bone-related parameters we could demonstrate the usefulness of our cell culture system to discriminate between primary (Col1a1) and secondary effects (Jag1) in osteoblasts.

Novel splice-site mutation in ATP8B1 results in atypical progressive familial intrahepatic cholestasis type 1

BACKGROUND AND AIM

Our objective was to identify the molecular genetic basis of an Alagille-like condition not linked to JAG1 or NOTCH2 in two related sibships.

METHODS

Because of common ancestry, and an autosomal recessive mode of inheritance, it was hypothesized that all affected and no unaffected individuals would be homozygous for the same haplotype in the region of the causative gene. Single nucleotide polymorphism arrays were therefore used to genotype 3 affected individuals from two sibships, their mothers and four unaffected siblings, to identify regions of homozygosity. Genes within the largest regions were prioritized and sequenced for mutations. Mutant RNA transcripts were also sequenced.

RESULTS

A novel splice acceptor site mutation in the ATP8B1 gene was identified (a G-C preceding exon 16 resulting in a 4  bp deletion and frameshift from the 5' end of exon 16). This result was unexpected because ATP8B1 mutations are associated with progressive familial intrahepatic cholestasis type 1 (PFIC1). Intrahepatic bile duct paucity, cardiac anomalies, renal tubular acidosis and hypothyroidism led to an initial diagnosis of Alagille syndrome. However, in retrospect, abnormal sweat chloride, normal gamma-glutamyl transferase, normal to low cholesterol, and an autosomal recessive mode of inheritance were consistent with PFIC1. Renal tubular acidosis, hypothyroidism and cardiac anomalies have not previously been associated with PFIC1.

CONCLUSION

This work expands the phenotypic spectrum of PFIC1, and highlights the overlap in clinical phenotype between Alagille syndrome and PFIC1. Knowledge of the causative mutation allows for carrier testing and prenatal diagnosis in this community.

Paucity of intrahepatic bile ducts in neonates: the first case series from iran

OBJECTIVE

Paucity of interlobular bile ducts (PIBD), defined as absence or marked decrease in the number of interlobular bile ducts, is one of the causes of neonatal cholestasis. Treatment includes treating the intractable pruritus caused by persistent cholestasis. PIBD can be part of a familial syndrome of cholestasis named Alagille syndrome (AGS). We report clinical status of a case series of Iranian patients with PIBD.

METHODS

In this retrospective study, patients with cholestasis admitted to the pediatric gastroenterology ward in a referral hospital in Shiraz from January 2006 to January 2010 and underwent liver biopsy were evaluated. Clinical and paraclinical status of children with the pathologic diagnosis of PIBD was assessed.

FINDINGS

Disease was presented in all jaundiced patients with aged in average 3 days at presentation. Seven patients had the criteria of AGS. Despite medical treatment, cholestasis was not controlled in 6 (28.6%) patients. Liver transplantation led to the survival of 5 patients while the other patient who did not undergo liver transplantation died at 2 months of age. One patient underwent peritoneal dialysis due to renal insufficiency and died at 9 months of age. After 1-5 years of follow-up, the mortality rate was 9.5%.

CONCLUSION

In patients with intractable cholestasis, only patients that underwent liver transplantation survived. Thus, the most important criterion for liver transplantation in neonatal PIBD is intractable cholestasis. This is the first report that shows AGS can result in neonatal-onset renal insufficiency.

Alagille syndrome and Wilson disease in siblings: a diagnostic conundrum

The authors describe two siblings, each with a different, rare genetic condition that affects liver function. The index case, the 18-year-old asymptomatic brother of a young man recently diagnosed with Wilson disease, presented for Wilson disease screening and was also found to have abnormal liver function suggestive of cholestasis. However, ceruloplasmin level, 24 h urine copper concentration and liver synthetic function were normal. Further hepatic investigations and genetic mutation analysis were performed, ultimately leading to a diagnosis of Alagille syndrome. He was treated with ursodiol, which resulted in normalization of his liver function tests. Subsequently, he was found to be a carrier for a mutation in the Wilson disease gene, ATP7B. In the present report, the potential implications of being a heterozygote for Wilson disease in the context of Alagille syndrome are discussed. Also stressed is that care must be exercised by the clinician when diagnosing family members who may present with two different disorders closely mimicking one another.

Functional analysis of the Notch ligand Jagged1 missense mutant proteins underlying Alagille syndrome

Heterozygous mutations in the JAG1 gene, encoding Notch ligand Jagged1, cause Alagille syndrome (ALGS). As most of the mutations are nonsense or frameshift mutations producing inactive truncated proteins, haplo-insufficiency is considered the major pathogenic mechanism of ALGS. However, the molecular mechanisms by which the missense mutations cause ALGS remain unclear. Here we analyzed the functional properties of four ALGS missense mutant proteins, P163L, R184H, G386R and C714Y, using transfected mammalian cells. P163L and R184H showed Notch-binding activities similar to that of the wild-type when assessed by immunoprecipitation. However, their trans-activation and cis-inhibition activities were almost completely impaired. These mutant proteins localized mainly to the endoplasmic reticulum (ER), suggesting that the mutations induced improper protein folding. Furthermore, the mutant proteins bound more strongly to the ER chaperone proteins calnexin and calreticulin than the wild-type did. C714Y also localized to the ER, but possessed significant trans-activation activity and lacked enhanced binding to the chaperones, indicating a less severe phenotype. The properties of G386R were the same as those of the wild-type. Dominant-negative effects were not detected for any mutant protein. These results indicate that accumulation in the ER and binding to the chaperones correlate with the impaired signal-transduction activities of the missense mutant proteins, which may contribute to the pathogenic mechanism of ALGS. Our findings, which suggest the requirement for cell-surface localization of Jagged1 for cis-inhibition activities, also provide important information for understanding the molecular basis of Notch-signaling pathways.

Modeling SNP mediated differential targeting of homologous 3'UTR by microRNA

We had previously proposed that the post-transcriptional regulation through microRNA as a mechanism for incomplete penetrance and variable expressivity, leads to lack of correlation between genotype and phenotype. Here we report the validation of miRNA-target interactions we predicted earlier and demonstrate the regulation of endogenous JAG1 by hsa-miR-214 and hsa-miR-124, and TGFBR2 by hsa-miR-34b*, through luciferase activity of reporter constructs and also the expression levels of the endogenous genes. Using these targets, we have modeled the diploid state for miRNA target site with heterozygosity for the SNP and demonstrate the differential targeting of an otherwise identical 3'UTR. We show that SNP rs8708 (A > G) at the target site of hsa-miR-214 can relieve the repression while an SNP rs11466532 (C > T) enhances the repression of reporter expression by hsa-miR-34b*. We discuss the results in the light of its implications in the context of penetrance of dominant mutations in miRNA targeted genes, using JAG1 as an example. These observations imply that disease causing mutations in JAG1 linked to the SNP rs8708G will be poorly targeted by hsa-miR-214 when present against a normal allele of JAG1 with rs8708A and will show penetrance of JAG1 mutations as Alagille syndrome, while mutant JAG1 linked to rs8708A against rs8708G on the normal allele will show either no disease or much attenuated symptoms and hence exhibit incomplete penetrance.