P1163 ALL-ORAL THERAPY WITH DACLATASVIR IN COMBINATION WITH ASUNAPREVIR AND BMS-791325 FOR TREATMENT-NAIVE PATIENTS WITH CHRONIC HCV GENOTYPE 4 INFECTION

Biliary atresia (BA) is a progressive fibro-inflammatory cholangiopathy affecting the intraand extrahepatic bile ducts of neonates. Although BA is the most common identifiable cause of obstructive jaundice in infants, and is the leading indication for pediatric liver transplantation, the etiology remains elusive. We investigated the importance of genes identified in genome-wide association studies (GWAS) of BA patients using zebrafish. The Matthews's lab has demonstrated the utility of the zebrafish system to test the functionality of genes identified in GWAS of BA by demonstrating that knockdown of gpc1 leads to biliary defects. A prior GWAS examined single-nucleotide polymorphisms in 200 Han Chinese BA patients and 481 ethnically matched controls. The strongest association was found for a region located between the XPNPEP1 and ADD3 genes on 10q24.2. Our genetic analysis confirmed the importance of this region in a separate cohort of patients. To determine whether loss of xpnpep1 and/or add3a leads to biliary defects we performed knockdown studies of the respective genes using morpholino antisense oligonucleotides (MO). We then examined their biliary function using the lipid reporter PED6, biliary development using cytokeratin immunostaining, and gene expression using quantitative PCR. We confirmed that xpnpep1 and add3a are expressed in the developing zebrafish liver. Knockdown of add3a led to decreased biliary function by PED6 screening, while xpnpep1 knockdown had only a mild effect. There were developmental biliary defects in the add3a morphants, as demonstrated by cytokeratin immunostaining. The transcription factor vhnf1, implicated in biliary development, was significantly downregulated in add3a morphants but not xpnpep1 morphants. add3a morphants also demonstrated increased expression of gli2a, a Hedgehog target, which is consistent with prior studies of BA patients and of zebrafish models of BA such as gpc1 knockdown. Interestingly, knockdown of both add3a and gpc1 resulted in a synergistic disruptive effect on biliary development. While GWAS identified ADD3 and XPNPEP1 as potential BA susceptibility genes, our results suggest that ADD3 is likely the more important gene in this regard. Like gpc1, add3a acts via Hedgehog signaling, supporting a role for this important pathway in BA pathogenesis.