Study On The Pathogenesis Of C3 Glomerulopathy Caused By Factor H Mutation

Background and Objective:C3 glomerulopathy?C3G?is a severe kidney disease characterized by dysregulation of the alternative pathway of complement?AP?activation.Different mutations in the complement genes or complement-antibody have been identified in human C3 glomerulopathy patients.Factor H?FH?is an important regulator,mutations in which could cause inappropriate activation in the complement alternative pathway,and already have found in animals and humans that are associated with several kidney pathologies.Though the pathogenesis of C3G has not been inadequately understood yet,it is generally believed that mutations in CFH resulting in impairment of fluid phase complement regulation.And dysfunction of the complement alternative pathway in the fluid phase underlies C3 glomerulopathy.So far about the precise mechanisms are still remained as a much-debated topic and creating numerous controversies.During the analysis of the AP-related kidney diseases in previous researches,we found and selected two different kinds of single amino acid mutation:R1210C and R1215G that both located in Factor H SCR20domain.Complement FH gene is highly conserved between mice and humans with high sequence identity.The D1210C and R1215G changes in mouse FH corresponded to R1210C and R1215G mutations in human FH,respectively.Therefore,by introducing these two mutations?D1210C and R1215G?to mouse FH by gene targeting,we hope to establish an FH-related disease model in order to have a better understanding of the physiological role of FH as a cell surface complement regulator.Methods:By gene targeting,we have generated transgenic mice models with two different kinds of mutations:D1210C mutation and R1215G mutation.By performing various biochemical experiments,we analyze and compare the differences between FH^C/C mice and FH^G/G mice,at morphological,cellular and molecular levels as well the phenotype of these two mice stains.These data serve as a profound proof,we had focused on investigating and exploring the pathogenesis of C3 Glomerulopathy.We also presented the data of blocking f P function by antibody in FH^G/G mice,to provide new insights for the future therapeutic strategies for f H mutation related renal disease.Results:The D1210C mutation and R1215G mutation both locate in SCR 20 of FH.SCR 19 and 20 at the C terminus are critical for FH binding host cells on the cell surface.Mutation in the mouse FH SCR19 and 20 impaired its interaction with host cells and causing dysfunction in complement.Here we found from two stains of an FH-mutant mice:FH^C/C mice and FH^G/G mice,which show fairly similar condition of the fluid phase dysregulation,however,only FH^G/G mice show the presence of C3deposits in both mesangial areas and along the glomerular basement membrane?GBM?——typical C3G histopathology pattern,whereas FH^C/C mice showed neither a clinical nor histological sign of abnormality.With the similar condition of factor H plasma complement-regulating activity,only FH^G/G mice show the C3G phenotype.Accordingly,we proposed a new hypothesis:the impacted cell surface protection by complement factor H is the essential part in the pathogenesis of C3G,instead of by dysregulation in the complement fluid phase.The results of blocking Properdin activity in FH^G/G mice further prove our point that the intact function of Factor H's interaction with host cells plays a key role in the development of Factor H related C3glomerulopathy.Currently,no validated effective therapeutic approaches for C3G are available.Therefore,to fully elucidate the pathogenesis mechanism of C3 glomerulopathy has a significant meaning.Base on our new aspect and assumption about the pathogenesis of C3G,may enlighten us on the anti-complement therapy for C3glomerulopathy patients.