Screening Of Pedigrees Of Primary Biliary Cholangitis And Exploration Of Rare Mutations By Whole Exome Sequencing

【Background】Primary biliary cholangitis(primary biliary cholangitis,PBC)is a kind of chronic progressive intrahepatic cholestasis disease.The pathogenesis of PBC is not yet clear.Genetic researches found that the first-degree relatives of PBC patients have up to 100-fold higher risk of developing PBC,while the concordant rates for identical twins of PBC(up to 77%)were far higher than other autoimmune diseases,which indicates that genetic factors play an important role in the occurrence or development of PBCIn recent years,the genetic researches of PBC have achieved many new breakthroughs and progress.In addition to human leukocyte antigen gene,which has already been proved the association of the onset of PBC,genome-wide association analysis also found at least 40 susceptibility loci of non-HLA genes.However,these loci still cannot fully explain the pathogenesis of PBC,while these studies mainly focused on the sporadic patients and rarely covered the genetic analysis of familiar patients.Our study focused on the feature of familial aggregation in PBC,and then screening of familiar PBC patients,comparing the similarities and differences of various clinical indicators between familiar patients and sporadic patients.What’s more,whole exome sequencing technology was applied to screen for rare mutation in familiar PBC patients,aiming to preliminary explore the pathogenesis of patients in PBC pedigree.【Objectives】1.To screen for familiar PBC patients,and to compare the similarities and differences of various clinical profiles between familiar PBC patients and sporadic PBC patients.2.To apply whole exome sequencing to screening for rare mutation in familiar PBC patients and to explore the pathogenesis of patients in PBC pedigree preliminarily.【Methods】A total of 435 PBC patients between 2005 to 2016 were enrolled in this study.According to the autoantibodies of first-degree relatives and other diagnostic methods,we screen for familiar PBC patients.Clinical data of these patients were collected from medical records before and after treatment.Statistical methods were used to analyze the serum biochemical profiles,response rate between familiar PBC patients and sporadic PBC patients.Whole exome sequencing technology was applied to screen for the shared rare mutations in PBC pedigree.To confirm the special genetic background and explore the pathogenesis of PBC preliminarily,Mass ARRAY was used to validate these low-frequency loci in sporadic PBC patiens.【Results】1.A total of 435 cases of PBC patients and 946 first-degree relatives were screened,among which 18 of them(distributed in 16 families)were diagnosed as PBC.The incidence of first-degree relatives diagnosed as PBC were 1.90%,and the incidence of PBC pedigree was 3.68%.2.The level of RBC、HGB、PLT、ALT、AST、ALB、GLB、TBIL、ALP、GGT、CHO、TG、BUN、CRE、AMA、AMA-M2、anti-3E-BPO,anti-SP100,anti-GP210 between familiar patients and poradic patients show no significant differences before and after treatment.According to Paris I,Paris II and Barcelona criteria respectively,biochemical response rates of familiar patients group were 69.6%,65.2% and 69.6%,much higher than that of sporadic patients group,which were 54.5%,45.8% and 54.5%.According to UK-PBC risk score,the risk score of the familiar group was lower than that of the sporadic group.3.According to the principle that family selected should include as more patents as possible,two pedigrees(6 PBC patients and normal controls)were selected for whole exome sequencing.The results verified that rs79267778(HELZ2)which was reported to by associated with PBC shared by two PBC pedigrees.The results showed that patients of pedigee A share 319 rare mutations,patients of pedigree B share 355 rare mutations,and a total of 18 rare mutations are shared by two PBC pedigrees(including 16 SNPs and 2 In Dels).By the use of functional analysis,one genes related to autoimmunity and two genes relavant to bile acid metabolism were selected for further verification.4.Mass ARRAY aimed at the above 3 loci were implemented on 249 sporadic PBC patients,which found that rs147270307(CYP3A43)may be associcated with PBC.【Conclusions】1.It was confirmed that family aggregation really exist in PBC,and the risk of first-degree relatives was significantly higher than that of the general population.2.Familiar PBC patients have lower histological stage and better biochemical response rate and prognosis than sporadic patients.This benefit should owe to early screening of family patients.So,it is of great significance for early screening of PBC pedigrees.3.There were shared low-frequency mutations between familiar PBC patients,the loci rs79267778(HELZ2)、rs147270307(CYP3A43)may be related to the pathogenesis of PBC.