| Background.Atypical hemolytic uremic syndrome(a HUS)has been demonstrated to be a disorder of the regulation of the complement alternative pathway,which is associated with mutations in complement genes.Because mutations in different complement genes in a HUS patients have values in making optimal patient care decision,judging prognosis and identifying patients who could safely benefit from kidney transplant,mutation screening of all complement genes associated with a HUS should be performed in each patient.Approximately 50 % of a HUS patients have been reported to have mutations in the complement genes.To our knowledge,however,the prevalence of mutations in the complement genes in Chinese children with a HUS is not known.Therefore,we performed mutational analysis of the 10 known complement genes(CFH,MCP,CFI,C3,CFB,CFHR1,CFHR2,CFHR3,CFHR4 and CFHR5)in11 Southern Han Chinese children with a HUS.Methods.Peripheral blood samples were collected for genetic analysis from 11 Southern Han Chinese children with a HUS.Healthy Southern Han Chinese from 1000 Genomes Project were studied as controls.We performed mutational analysis of the exomes of the 10 complement genes inclusive 25 bases from 3’ end and 25 bases from 5’end in the 11 Southern Han Chinese children with a HUS by targeted sequencing.We focused on non-synonymous variants,stopgain variants,stoploss variants,splice acceptor and donor site variants and coding insertions or deletions which were reported to be pathogenic mutations or polymorphisms associated with a HUS in Pubmed or a HUS mutation database,or present in the 1000 G with a minor allele frequency value <1% or not present in the 1000 Genomes Project.Significant variants detected by targeted sequencing were subsequently validated by resequencing using Sanger sequencing.To assign pathogenicity of mutations found in the complement genes,we investigated genetic conservation by multiple nucleotide sequence alignment and multiple protein sequence alignment among different species.And then we evaluated the physical and chemical properties and structure characteristics of the affected amino acids,and analysed whether the variants were located in protein domains or not.The functional significance was also investigated by functional computational prediction methods at last.To assign pathogenicity of polymorphism found in the complement genes,we examined the allelic frequencies of polymorphism between the 11 a HUS patients and Southern Han Chinese controls.Results.Fifty-three unique variants were detected in the 10 complement genes of the 11 a HUS patients.After screening,resequencing and analysising,two pathogenic mutations,CFB 221G>A(R74H)and a novel mutation CFHR5 242C>T(P81L),were identified in 3(27.27%)of the 11 a HUS patients.A polymorphism which was reported to be associated with a HUS,CFH 2808G>T,was detected in 9 of the 11 patients.There was no significant difference in the allelic frequencies of this polymorphism between the 11 a HUS patients and Southern Han Chinese controls.Conclusions.Our investigation supports the necessity of searching for mutations in all the complement genes in Southern Han Chinese children with a HUS. |
