Project description:Biliary atresia (BA) is a rare cholestatic disease of unknown etiology that affects infants and shows an incidence of 1 out of 18,000 live births in Europe (1). The first therapeutic option is a timely performed portoenterostomy. However, the majority of patients suffer from a progressive inflammatory process, which leads to complete destruction of the extra- and intrahepatic biliary system followed by end-stage liver cirrhosis. Hence, BA is the leading indication for pediatric liver transplantation worldwide (2, 3). To understand the pathogenesis of the disease and improve theoutcome of BA patients, research has focused on the inflammatory process in liver and bile ducts, in which several factors are remarkably elevated, such as activated CD4 and CD8 T-cells, TNF alpha,IFN alpha and other proinflammatory TH1 cytokines (3-8). By the time of diagnosis, however, the disease has already reached an advanced state, characterized by the complete obstruction of the extrahepatic bile ducts with impaired bile flow and fibrosis or cirrhosis of the liver. Therefore, studies in humans focusing on the trigger mechanism of BA are limited due to the paucity of liver and availability of bile duct tissue for research. One infectious animal model has been developed, in which newborn Balb/c mice exclusively show the experimental BA phenotype after infection with rhesus rotavirus (RRV) (9, 10). This model allows the analysis of the inflammatory reactions in liver and bile ducts at early steps in the development of bile duct atresia (11-20). Furthermore, inbred mouse strains have been shown to have a different susceptibility for the development of experimental BA, suggesting that Balb/c mice have an immunological gap responsible for disease progression (10, 12). The aim of this study was to identify key genes responsible for the BA phenotype by comparing the transcriptomes at an early time point after virus infection, i.e. before bile duct atresia, between two mouse strains with different susceptibilities to BA. Differences in the virus titration and the clinical course of infected mice were analyzed, and variations in the hepatic gene response assessed by comparative microarray assays were correlated to variances in the hepatic inflammatory reaction. Balb/c mice and C57Black/6 (Black/6) mice were infected with RRV postpartum and signs of BA and survival were noted. Liver sections of diseased, healthy and control animals were assessed for T-cell expression, and the virus loads were determined. Second, mice were sacrificed after three days, and isolated hepatic RNA was subjected to gene expression analysis using Affymetrix Gene Chip MOE 430 2.0.We compared three individual expression profiles from RRV-infected Balb/c mice against 2 individual expression profiles from RRV-infected C57/BL6 control mice using the Affymetrix GeneChip MOE 430 2.0.

Project description:Biliary atresia (BA) is a rare cholestatic disease of unknown etiology that affects infants and shows an incidence of 1 out of 18,000 live births in Europe (1). The first therapeutic option is a timely performed portoenterostomy. However, the majority of patients suffer from a progressive inflammatory process, which leads to complete destruction of the extra- and intrahepatic biliary system followed by end-stage liver cirrhosis. Hence, BA is the leading indication for pediatric liver transplantation worldwide (2, 3). To understand the pathogenesis of the disease and improve theoutcome of BA patients, research has focused on the inflammatory process in liver and bile ducts, in which several factors are remarkably elevated, such as activated CD4 and CD8 T-cells, TNF alpha,IFN alpha and other proinflammatory TH1 cytokines (3-8). By the time of diagnosis, however, the disease has already reached an advanced state, characterized by the complete obstruction of the extrahepatic bile ducts with impaired bile flow and fibrosis or cirrhosis of the liver. Therefore, studies in humans focusing on the trigger mechanism of BA are limited due to the paucity of liver and availability of bile duct tissue for research. One infectious animal model has been developed, in which newborn Balb/c mice exclusively show the experimental BA phenotype after infection with rhesus rotavirus (RRV) (9, 10). This model allows the analysis of the inflammatory reactions in liver and bile ducts at early steps in the development of bile duct atresia (11-20). Furthermore, inbred mouse strains have been shown to have a different susceptibility for the development of experimental BA, suggesting that Balb/c mice have an immunological gap responsible for disease progression (10, 12). The aim of this study was to identify key genes responsible for the BA phenotype by comparing the transcriptomes at an early time point after virus infection, i.e. before bile duct atresia, between two mouse strains with different susceptibilities to BA. Differences in the virus titration and the clinical course of infected mice were analyzed, and variations in the hepatic gene response assessed by comparative microarray assays were correlated to variances in the hepatic inflammatory reaction.

Project description:Biliary atresia causes jaundice and liver failure in newborn children. In this study, single nucleotide polymorphisms were characterized in children with biliary atresia and identified ARF6 as a susceptibility gene for this disease. Knockdown of this gene in zebrafish embryos impaired formation of bile ducts and excretion of bile from the zebrafish liver. Subject enrollment: Children with biliary atresia were enrolled at Children's Hospital of Pittsburgh (CHP) after obtaining written consent from parents for the University of Pittsburgh IRB approved protocol number 0405628. At the Center for Applied Genomics (CAG), all subjects were enrolled after obtaining written consent from parents per Children's Hospital of Philadelphia IRB approval number 06-004886 Genotyping array: Genotyping of DNA obtained from blood was performed with the Infinium HumanHap550K BeadChip (Illumina, San Diego, CA). Statistical methods and software: SNP genotype frequencies were compared between cases and controls with a chi-square test statistic applied in Plink [Purcell et al, 2007] for SNPs with at least 90% call rate and 1% minor allele frequency (MAF). Cases and controls: All DNA samples had excellent data quality with call rates > 98%. A total of 63 Caucasian BA cases and 1907 controls were compared at > 550000 SNPs, and demonstrated a very low genomic inflation factor of 1.00627. Description of Cases: Biliary atresia patients had received a Kasai procedure and demonstrated histopathological features of biliary obstruction, and were recruited at evaluation for transplantation or after liver transplantation. Reference: Purcell S, Neale B, Todd-Brown K, Thomas L, Ferreira MA, et al. (2007) PLINK: a tool set for whole-genome association and population-based linkage analyses. Am J Hum Genet 81: 559-575 (PMID: <a href="http://www.ncbi.nlm.nih.gov/pubmed/?term=17701901">17701901</a>).

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Systems analysis of biliary atresia through integration of high-throughput biological data

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