Caratterizzazione molecolare dei difetti genici associati a Colestasi intraepatica familiare progressiva mediante Next Generation Sequencing

Progressive Familial Intrahepatic Cholestasis (PFIC) is a group of autosomal recessive diseases that affects especially newborns and children, with progression to liver failure in the first decades of life. PFIC is classified into five types based on the genetic defect involved in bile transport. It is caused by homozygous or compound heterozygous mutations in ATP8B1, ABCB11, ABCB4, TJP2 and NR1H4 genes. Other benign late-onset phenotypes and non-progressive forms (BRIC, LPAC, DIC and ICP) are caused by heterozygous mutations in the same gene pattern. Other genes have been recently involved in both progressive and non-progressive forms. The aim of the project is to develop and validate a broad, reliable, rapid and cost-saving NGS genetic test for PFIC patients. 96 patients were tested for the first described genes and 80 patients were sequenced with the latest discovered candidate genes for PFIC and other related benign phenotypes. Bioinformatic and statistic pipelines were applied. A total of 184 different variants has been identified in our cohort: 18 pathogenic, 46 VUS, 44 likely benign and 76 benign. P/LP mutations were found in 12% of patients: 2 in ATP8B1, 3 in ABCB11, ABCB4 and TJP2 each, one in ABCC2, JAG1, NOTCH2. Many patients had multiple variants in several genes. Patients had from 7 to 35 variants each and some SNPs were significantly associated with biochemical parameters and phenotypic features (e.g. liver fibrosis) that could better explain clinics and accelerate the progression to liver failure. Our detection rate is according to other studies proposing multi-gene panels. Our analysis may be useful for the molecular diagnostics of PFIC and a better characterization and understanding of the linking between molecular defects and different subtypes of the disease. The high SNPs prevalence let us to hypothesize a synergistic haplotype effect in determining different multifactorial cholestasis phenotypes and overlapping features.