Binita M. Kamath

Vascular anomalies in Alagille syndrome: a significant cause of morbidity and mortality.

Background—Alagille syndrome (AGS) is a dominantly inherited multisystem disorder involving the liver, heart, eyes, face, and skeleton, caused by mutations in Jagged1. Intracranial bleeding is a recognized complication and cause of mortality in AGS. There are multiple case reports of intracranial vessel abnormalities and other vascular anomalies in AGS. The objective of this study was to characterize the nature and spectrum of vascular anomalies in AGS. Methods and Results—Retrospective chart review of 268 individuals with AGS was performed. Twenty-five patients (9%) had noncardiac vascular anomalies or events. Sixteen patients had documented structural vascular abnormalities. Two had basilar artery aneurysms, 7 had internal carotid artery anomalies, and another had a middle cerebral artery aneurysm. Moyamoya disease was described in 1 patient. Three of the 16 patients had aortic aneurysms, and 2 had aortic coarctations. One of the patients with a basilar artery aneurysm also had coarctation of the aorta. One of the individuals with an internal carotid artery anomaly also had renal artery stenosis. Nine more patients had intracranial events without documented vessel abnormalities. Vascular accidents accounted for 34% of the mortality in this cohort. Conclusions—The vascular anomalies described in our cohort of AGS individuals identify an underrecognized and potentially devastating complication of this disorder. It is a major cause of morbidity and mortality in this population, accounting for 34% of the mortality. We have also reviewed the body of evidence supporting a role for Jagged1 and the Notch signaling pathway in vascular development.

Consequences of JAG1 mutations

Background: Alagille syndrome (AGS) is a multi-system, autosomal dominant disorder with highly variable expressivity, caused by mutations within the Jagged1 (JAG1) gene. Methods: We studied 53 mutation positive relatives of 34 AGS probands to ascertain the frequency of clinical findings in JAG1 mutation carriers. Results: Eleven of 53 (21%) mutation positive relatives had clinical features that would have led to a diagnosis of AGS. Seventeen of the 53 (32%) relatives had mild features of AGS, revealed only after targeted evaluation following the diagnosis of a proband in their family. Twenty five of the 53 (47%) mutation positive relatives did not meet clinical criteria, and two of these individuals had no features consistent with AGS at all. The frequency of cardiac and liver disease was notably lower in the relatives than in the probands, characterising the milder end of the phenotypic spectrum. The characteristic facies of AGS was the feature with the highest penetrance, occuring almost universally in mutation positive probands and relatives. Conclusions: This study has implications for genetic counselling of families with AGS and JAG1 mutations.

Mutations in TJP2 cause progressive cholestatic liver disease

Elucidating genetic causes of cholestasis has proved to be important in understanding the physiology and pathophysiology of the liver. Here we show that protein-truncating mutations in the tight junction protein 2 gene (TJP2) cause failure of protein localization and disruption of tight-junction structure, leading to severe cholestatic liver disease. These findings contrast with those in the embryonic-lethal knockout mouse, highlighting differences in redundancy in junctional complexes between organs and species.

NOTCH2 mutations in Alagille syndrome

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

Listeria meningitis after treatment with infliximab.

Tumor necrosis factor (TNF)– is a proinflammatory cytokine with a pivotal role in the pathophysiology of chronic inflammatory conditions such as Crohn disease and rheumatoid arthritis (1,2). The use of infliximab, a chimeric anti–TNFmonoclonal antibody, has shown clinical efficacy in treating moderate to severe Crohn disease in adult and pediatric patients (3–5). Several studies in patients with Crohn disease have cited low rates of adverse effects in comparison with placebo (6,7). The exact mechanisms of the action of infliximab are unclear. Although infliximab clearly neutralizes the biologic activity of TNF, the complete picture is more complex. A recent study examined the antiinflammatory and immunomodulatory activity of infliximab in patients with Crohn disease and concluded that infliximab exerts its immunologic effects at a local level in the bowel mucosa without generally suppressing systemic immune function (8). This implies that patients treated with infliximab are not at increased risk of serious opportunistic infections. We describe an adolescent with Crohn disease in whom listeria meningitis developed 3 days after an infusion of infliximab. Listeria monocytogenes (L. monocytogenes) infection has been well documented in pregnant women, neonates, and immunosuppressed patients (9,10). Furthermore, listeria septicemia has been reported in an adult patient with Crohn disease 4 days after the administration of infliximab (11). However, infection with listeria after infliximab administration has never been reported in the pediatric population.

Directed differentiation of cholangiocytes from human pluripotent stem cells

Although bile duct disorders are well-recognized causes of liver disease, the molecular and cellular events leading to biliary dysfunction are poorly understood. To enable modeling and drug discovery for biliary disease, we describe a protocol that achieves efficient differentiation of biliary epithelial cells (cholangiocytes) from human pluripotent stem cells (hPSCs) through delivery of developmentally relevant cues, including NOTCH signaling. Using three-dimensional culture, the protocol yields cystic and/or ductal structures that express mature biliary markers, including apical sodium-dependent bile acid transporter, secretin receptor, cilia and cystic fibrosis transmembrane conductance regulator (CFTR). We demonstrate that hPSC-derived cholangiocytes possess epithelial functions, including rhodamine efflux and CFTR-mediated fluid secretion. Furthermore, we show that functionally impaired hPSC-derived cholangiocytes from cystic fibrosis patients are rescued by CFTR correctors. These findings demonstrate that mature cholangiocytes can be differentiated from hPSCs and used for studies of biliary development and disease.

Differing Effects of Rapamycin or Calcineurin Inhibitor on T‐Regulatory Cells in Pediatric Liver and Kidney Transplant Recipients

In a cross‐sectional study, we assessed effects of calcineurin inhibitor (CNI) or rapamycin on T‐regulatory (Treg) cells from children with stable liver (n = 53) or kidney (n = 9) allografts several years posttransplant. We analyzed Treg number, phenotype, suppressive function, and methylation at the Treg‐specific demethylation region (TSDR) using Tregs and peripheral blood mononuclear cells. Forty‐eight patients received CNI (39 as monotherapy) and 12 patients received rapamycin (9 as monotherapy). Treg numbers diminished over time on either regimen, but reached significance only with CNI (r =−0.424, p = 0.017). CNI levels inversely correlated with Treg number (r =−0.371, p = 0.026), and positively correlated with CD127+ expression by Tregs (r = 0.437, p = 0.023). Patients with CNI levels >3.6 ng/mL had weaker Treg function than those with levels <3.6 ng/mL, whereas rapamycin therapy positively correlated with Treg numbers (r = 0.628, p = 0.029) and their expression of CTLA4 (r = 0.726, p = 0.041). Overall, CTLA4 expression, TSDR demethylation and an absence of CD127 were important for Treg suppressive function. We conclude that rapamycin has beneficial effects on Treg biology, whereas long‐term and high dose CNI use may impair Treg number, function and phenotype, potentially acting as a barrier to attaining host hyporesponsiveness to an allograft.

Intracranial vascular abnormalities in patients with Alagille syndrome

Objectives: To define the spectrum of intracranial events and cerebrovascular lesions in patients with Alagille syndrome using magnetic resonance imaging with angiography of the head and medical histories and to correlate the presence of lesions with the clinical outcome of bleeding or ischemic intracranial events. Methods: 26 patients with Alagille syndrome underwent magnetic resonance imaging with angiography of the head; 22 had no symptoms and underwent study for screening purposes and 4 were symptomatic with neurologic changes. The results of studies and the history of ischemic intracranial events were reviewed. Results: Cerebrovascular abnormalities were detected in 10 of 26 (38%) patients (9 by head magnetic resonance imaging with angiography and 1 by necropsy). The findings included stenoses of the internal carotid arteries unilaterally (n = 5) or bilaterally (n = 3), basilar artery aneurysm (n = 1) and middle cerebral artery aneurysm (n = 1). Among the 9 patients with cerebrovascular abnormalities detected by magnetic resonance imaging with angiography, 5 had no symptoms (23%, 5 of 22) and 4 were symptomatic. Thus, 100% of symptomatic patients had detected abnormalities and 23% of screened, asymptomatic patients had detected anomalies. Screening magnetic resonance imaging with angiography failed to detect vascular anomalies in 2 asymptomatic patients who had fatal ischemic intracranial events years later. There was evidence of progression of vascular abnormalities in 4 patients. Ischemic intracranial events occurred in 10 of 26 (38%) patients and were associated with cerebrovascular abnormalities in 6 of 10 patients. Conclusion: The cerebral vasculopathy of Alagille syndrome predominantly involves the internal carotid arteries. It is more prevalent than would be suggested by the number of symptomatic individuals, appears to be progressive and shares many similarities with moyamoya. Magnetic resonance imaging with angiography is useful to detect these lesions and may have a valuable role in screening for treatable lesions such as aneurysms.

Outcomes of liver transplantation for patients with alagille syndrome: The studies of pediatric liver transplantation experience

Alagille syndrome (ALGS) is a multisystem disorder that manifests as childhood cholestasis. Reports of liver transplantation (LT) for patients with ALGS have come largely from single centers, which have reported survival rates of 57% to 79%. The aim of this study was to determine LT outcomes for patients with ALGS. We performed a retrospective analysis of the Studies of Pediatric Liver Transplantation database, which contains information about 3153 pediatric LT recipients. Data were available for 91 patients with ALGS and for 236 age‐matched patients with biliary atresia (BA). The frequency of complex cardiac anomalies was lower in the LT group with ALGS versus published ALGS series (5% versus 13%). The pretransplant glomerular filtration rate (GFR) was <90 mL/minute/1.73 m2 in 18% of the LT patients with ALGS and in 5% of the LT patients with BA (P < 0.001). The height deficit at listing was worse for the ALGS patients (66%) versus the BA patients (22%). The 1‐year patient survival rates were 87% for the ALGS patients and 96% for the BA patients (P = 0.002). The deaths in the ALGS group mostly occurred within the first 30 days. No pretransplant factors associated with death were identified in the ALGS group. A survival analysis revealed that biliary (P = 0.02), vascular (P < 0.001), central nervous system (CNS; P < 0.001), and renal complications (P < 0.001) after LT were associated with death in the ALGS group. Renal insufficiency in the ALGS patients worsened after LT, and at 1 year, GFR was <90 mL/minute/1.73 m2 in 22% of the LT patients with ALGS but in only 8% of the patients with BA (P = 0.0014). More LT pediatric patients with ALGS either were currently receiving special education (50% versus 30% for BA patients, P = 0.02) or had received special education in the past (60% versus 36%, P = 0.01). Vascular, CNS, and renal complications were increased in the ALGS patients after LT, and this reflected multisystem involvement. Although the 1‐year survival rate was modestly lower for the ALGS patients versus the BA patients, the clustering of deaths within the first 30 days is notable and warrants increased vigilance and further investigation. Liver Transpl, 2012.

Genomic alterations in biliary atresia suggest region of potential disease susceptibility in 2q37.3.

Biliary atresia (BA) is a progressive, idiopathic obliteration of the extrahepatic biliary system occurring exclusively in the neonatal period. It is the most common disease leading to liver transplantation in children. The etiology of BA is unknown, although infectious, immune and genetic causes have been suggested. Although the recurrence of BA in families is not common, there are more than 30 multiplex families reported and an underlying genetic susceptibility has been hypothesized. We screened a cohort of 35 BA patients for genomic alterations that might confer susceptibility to BA. DNA was genotyped on the Illumina Human Hap 550 Beadchip platform, which analyzes over 550,000 single nucleotide polymorphisms (SNPs) for genomic deletions and duplications. Areas of increased and decreased copy number were compared to those found in control populations. To identify regions that could serve as susceptibility factors for BA, we searched for regions that were found in BA patients, but not in controls. We identified two unrelated BA patients with overlapping heterozygous deletions of 2q37.3. Patient 1 had a 1.76 Mb (280 SNP), heterozygous deletion containing 30 genes. Patient 2 had a 5.87 Mb (1,346 SNP) heterozygous deletion containing 55 genes. The overlapping 1.76 Mb deletion on chromosome 2q37.3 from 240,936,900 to 242,692,820 constitutes the critical region and the genes within this region could be candidates for susceptibility to BA.