Document Detail

A mutation in factor I that is associated with atypical hemolytic uremic syndrome does not affect the function of factor I in complement regulation.
MedLine Citation:
PMID:  17084897     Owner:  NLM     Status:  MEDLINE    
Factor I (FI) is the major complement inhibitor that degrades C3b and C4b in the presence of cofactors such as factor H (FH) and membrane cofactor protein (MCP). Recently, mutations and polymorphisms in complement regulator molecules FH and MCP but also in FI have been associated with atypical hemolytic uremic syndrome (aHUS). HUS is a disorder characterized by hemolytic anemia, thrombocytopenia and acute renal failure. In this study, we report three unrelated patients with an identical heterozygous mutation, G261D, in the FI heavy chain who developed severe aHUS at different time points in their lives. Two of the patients also have polymorphisms in FH previously associated with risk of developing aHUS. Testing in particular one patient and control serum samples we did not observe major differences in complement hemolytic activity, FI plasma levels or the capability to degrade C4b or C3b. A recombinant protein was produced in order to analyze the functional consequences of the mutation. Mutant FI had a slightly different migration pattern during electrophoresis under reducing conditions. An alteration due to alternative splicing or glycosylation was ruled out, thus the altered migration may be due to proximity of the mutation to a cysteine residue. The recombinant mutant FI degraded C3b and C4b in a manner comparable to wild-type protein. In conclusion, despite the association between the heterozygous mutation in FI and aHUS we did not observe any abnormalities in the function of FI regarding complement regulation.
Sara C Nilsson; Diana Karpman; Fariba Vaziri-Sani; Ann-Charlotte Kristoffersson; Rémi Salomon; Francois Provot; Veronique Fremeaux-Bacchi; Leendert A Trouw; Anna M Blom
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Publication Detail:
Type:  Clinical Trial; Comparative Study; Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-11-07
Journal Detail:
Title:  Molecular immunology     Volume:  44     ISSN:  0161-5890     ISO Abbreviation:  Mol. Immunol.     Publication Date:  2007 Mar 
Date Detail:
Created Date:  2006-12-04     Completed Date:  2007-03-29     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7905289     Medline TA:  Mol Immunol     Country:  England    
Other Details:
Languages:  eng     Pagination:  1835-44     Citation Subset:  IM    
Lund University, Department of Laboratory Medicine, University Hospital Malmö, S-205 02 Malmö, Sweden.
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MeSH Terms
Child, Preschool
Complement Activation* / genetics
Complement C3b / genetics,  metabolism
Complement C4b / metabolism
Complement Factor I / genetics*,  metabolism*
DNA Mutational Analysis
Exons / genetics
Hemolytic-Uremic Syndrome / genetics*,  metabolism*
Mutation, Missense*
Recombinant Proteins / genetics,  metabolism
Reg. No./Substance:
0/Recombinant Proteins; 80295-43-8/Complement C3b; 80295-50-7/Complement C4b; EC Factor I

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