Identification And Characterzations Of Novel ADRB3 Mutations In Chinese Familial Gout Pedigrees

Objective: Gout is recognized as a familial disorder and the group of gout patients with a family history is called familial gout.Familial gout should be a polygenic hereditary disease predominantly,composed of many susceptible genes.However,there are few susceptible genes associated with familial gout were reported yet.The ?3-adrenergic receptor(?3-AR)is mainly expressed in adipose tissue in human.To date,multi-ethnic,multitiered,large-scale genetic association studies have confirmed ADRB3 as a gout-risk gene.However,the patients in above studies are unfamilial gouty patients.At present,there are no reports about the genetic susceptibility of ADRB3 and familial gout.we aim to identify and characterize ADRB3 mutations in a large cohort of Chinese Han male familial gout patients,and dicuss the relationship of genetic susceptible of familial gout and ADRB3.Then we detect whether the novel mutations influence the expression level of the ?3-AR and impaire the cAMP accumulation activity of the ?3-AR.Methods: 500 unrelated Chinese Han male patients with familial gout and 600 unrelated control individuals were recruited.The coding exons and flanking introns of the ADRB3 were sequenced in all participants.Novel mutations were recreated by site-directed mutagenesis and tested for their effect on ADRB3 expression and function in transfected 293 T cells.western blot,and cAMP assay were used to determine protein expression and ADRB3 function,respectively.Results: Two novel heterozygous missense ADRB3 variants c.113 C>T p.Ala38 Val and c.1026 C>G p.Asn342 Lys were detected in probands of family A and family B,respectively.Analysis of the two pedigrees showed that p.Ala38 Val and p.Asn342 Lys cosegregated with gout with complete penetrance.Both of the two mutations were absent in 600 control individuals.Further in vitro study indicate that cell lines stably expressing p.Ala38 Val and p.Asn342 Lys mutants significantly down-regulated the expression level of the ADRB3 and showed impaired cAMP accumulation activity.Conclusion: We for the first time identified and characterized ADRB3 mutations in a large cohort of Chinese familial gout pedigrees.The study specifically demonstrated the role of novel mutationsp.Ala38 Val and p.Asn342 Lys down-regulated the expression level and impaired cAMP accumulation activity of the ADRB3,providing further evidence for genetic ADRB3 defects as a disease mechanism in familial gout.