Abstract

Populations that are small and under-studied present a particular problem for studying the genetics of multifactorial human traits, where normal variation and allele frequencies are uncharacterized. We present an investigation of biliary atresia (BA), a usually sporadic malformation of the biliary tree. Worldwide, BA leads to half of all paediatric liver transplants, and is always fatal without major surgical intervention. The causes of BA remain unknown; autoimmune processes and genetic background may both play a part. In New Zealand Māori and Polynesian populations the incidence is elevated three-fold compared to Europeans. We have identified a large Māori family (iwi) exhibiting an extremely elevated incidence of BA (1:100–300 live births). To circumvent some of the problems in studying complex traits in Maori we have adopted a non-parametric, family-based approach that maps long, Identical-By-State (IBS) segments across affected individuals. This allows investigation without reliance on pre-existing assumptions about allele frequencies, a definitive inheritance model or exclusion of unidentified phenocopies