Genetic contributors and modifiers of biliary atresia.

To date, the etiology and pathogenic underpinning of the progression of the most prevalent serious neonatal liver disease, biliary atresia, remains elusive. This disease presents as an aggressive form of neonatal cholestasis characterized by the destruction and obliteration of the extrahepatic bile ducts within the first few weeks of life and a rapid progression of biliary fibrosis, likely due to unremitting cholestasis and retention of biliary constituents including bile acids. In ∼5% of patients, biliary atresia is associated with laterality features, suggesting a genetic underpinning to a disease that begins soon after birth. However, biliary atresia does not occur within families and twins are discordant, indicating an absence of strict mendelian inheritance. Despite this, genes related to bile duct dysmorphogenesis/ciliopathies overlapping with features of biliary atresia in both humans and nonhuman model systems have been proposed. Taken together, strict genetic etiologies leading to a common pathway of a neonatal cholangiopathy resulting in biliary atresia remain elusive. Contributions from fibrogenesis- and inflammation-based studies suggest that early engagement of these pathways contributes to disease progression, but a recent double-blind study did not suggest any benefit from early use of corticosteroids. However, there are genetic contributions to the adaptation and response to cholangiopathies and cholestasis that may be present in certain populations that likely impact upon the response to hepatoportoenterostomy and subsequent biliary tract function. Studies utilizing next generation sequencing technologies (e.g., exome analysis) are ongoing in several laboratories around the world; they are expected to provide insights into genetic contributions to biliary atresia outcomes. Altogether, combinations of exome sequencing and large population studies are expected to reveal causative and modifying genes relevant to patients with biliary atresia as a means to provide therapeutic targets and potential opportunities for genetic screening.