HEPATOLOGY Novel splice-site mutation in ATP8B1 results in atypical Progressive Familial Intrahepatic Cholestasis Type 1 Emily Copeland,* Nisa Renault,* Marc Renault, § Sarah Dyack, † Dennis E Bulman, ‡ Karen Bedard,* Anthony Otley, † Fergall Magee,* ,† Philip Acott † and Wenda L Greer* ,† Departments of *Pathology and † Pediatrics, Dalhousie University, Halifax, Nova Scotia, and ‡ Ottawa Hospital Research Institute, Ottawa, Ontario, Canada; and § LIAFA, Université Paris Diderot-Paris 7, Paris, France Key words abnormal sweat chloride, bile duct paucity, Byler disease, cardiac anomaly, Progressive Familial Intrahepatic Cholestasis Type 1, renal tubular acidosis. Accepted for publication 11 September 2012. Correspondence Dr Wenda Greer, Division of Hematology, Department of Pathology and Laboratory Medicine, Capital District Health Authority, Mackenzie Building, 5788 University Avenue, Halifax, NS, Canada B3H 1V8. Email: wenda.greer@cdha.nshealth.ca Potential conflicts of interest: The authors report no conflict of interest. Abstract Background and Aim: Our objective was to identify the molecular genetic basis of an Alagille-like condition not linked to JAG1 or NOTCH2 in two related sibships. Methods: Because of common ancestry, and an autosomal recessive mode of inheritance, it was hypothesized that all affected and no unaffected individuals would be homozygous for the same haplotype in the region of the causative gene. Single nucleotide polymorphism arrays were therefore used to genotype 3 affected individuals from two sibships, their mothers and four unaffected siblings, to identify regions of homozygosity. Genes within the largest regions were prioritized and sequenced for mutations. Mutant RNA transcripts were also sequenced. Results: A novel splice acceptor site mutation in the ATP8B1 gene was identified (a G–C preceding exon 16 resulting in a 4 bp deletion and frameshift from the 5′ end of exon 16). This result was unexpected because ATP8B1 mutations are associated with Progressive Familial Intrahepatic Cholestasis Type 1 (PFIC1). Intrahepatic bile duct paucity, cardiac anomalies, renal tubular acidosis and hypothyroidism led to an initial diagnosis of Alagille Syndrome. However, in retrospect, abnormal sweat chloride, normal gamma-glutamyl transferase, normal to low cholesterol, and an autosomal recessive mode of inheritance were consistent with PFIC1. Renal tubular acidosis, hypothyroidism and cardiac anomalies have not previously been associated with PFIC1. Conclusion: This work expands the phenotypic spectrum of PFIC1, and highlights the overlap in clinical phenotype between Alagille Syndrome and PFIC1. Knowledge of the causative mutation allows for carrier testing and prenatal diagnosis in this community. Introduction Alagille Syndrome (AS) is an autosomal dominant condition asso- ciated with neonatal jaundice and cholestasis. 1 The diagnosis of AS is based on a paucity of interlobular bile ducts (IBDP) associ- ated with three to five major features including chronic cholestasis, cardiac disease, skeletal abnormalities, ocular abnormalities and a characteristic facial phenotype. 2–4 The condition is highly pen- etrant and expression is variable even within families. AS has been shown to result from mutations in the Jagged 1(JAG1) 5–7 or NOTCH2 8 genes. JAG1 encodes a ligand for the Notch receptor, which is involved in an intercellular signaling pathway important in embryonic development. 9 We previously 10 described a consanguineous Canadian First Nations Mi’kmaq family where five children in two related sib- ships were affected with an autosomal recessive form of an Alagille-like condition that was not linked to JAG1 or NOTCH2. Despite an initial diagnosis of AS, it was recognized that several clinical features of affected individuals were not typical for this diagnosis. The consistency and severity of presentation with neo- natal cholestasis is unusual in AS. There was also a lack of pos- terior embryotoxin and vertebral anomalies in the four fully evaluated patients and cardiac abnormalities were inconsistent among patients. Facial features typical of AS were equivocal. Most notably, the inheritance pattern was more in keeping with an auto- somal recessive form of inheritance. Individuals within this consanguineous community are at risk for being heterozygous carriers and having children affected with this severe disorder (three of five affected have died), yet there was no clinical test to identify carriers. It was therefore important to determine the genetic cause of disease to form the basis for a carrier test and possible prenatal diagnosis of affected fetuses. For this purpose, we used a strategy of autozygosity mapping that revealed a mutation within the ATP8B1 gene. This was unexpected because mutations in this gene have been associated with an alter- nate liver condition, Progressive Familial Intrahepatic Cholestasis doi:10.1111/j.1440-1746.2012.07290.x 560 Journal of Gastroenterology and Hepatology 28 (2013) 560–564 © 2012 Journal of Gastroenterology and Hepatology Foundation and Wiley Publishing Asia Pty Ltd