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A Phenotyping Regimen for Genetically Modified Mice Used to Study Genes Implicated in Human Diseases of Aging

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Disease-associated N-terminal complement factor H mutations perturb cofactor and decay-accelerating activities.

Isabell C Pechtl¹, David Kavanagh, Nicola McIntosh

¹School of Chemistry, University of Edinburgh, Edinburgh, Scotland, United Kingdom.

The Journal of Biological Chemistry

|January 29, 2011

Summary

Mutations in the N-terminal region of factor H (FH) can cause atypical hemolytic uremic syndrome (aHUS). These FH N-terminal mutations impair complement regulation, leading to aHUS pathogenesis.

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Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay

Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay

Published on: September 9, 2012

Area of Science:

Immunology
Molecular Biology
Genetics

Background:

Atypical hemolytic uremic syndrome (aHUS) is linked to mutations in factor H (FH), particularly in its C-terminal modules.
FH regulates complement activation, preferentially on self-membranes, and its dysfunction can lead to glomerular damage.

Purpose of the Study:

To investigate the impact of aHUS-associated mutations (R53H and R78G) in the N-terminal FH module (FH1-4) on complement regulation.
To explore the role of the I62V variation in FH1-4, previously linked to dense-deposit disease and age-related macular degeneration.

Main Methods:

Produced recombinant FH1-4 variants with specific mutations (R53H, R78G, I62V).
Assessed C3b binding affinities using surface plasmon resonance.
Quantified cofactor and decay-accelerating activities for complement regulation.

Main Results:

Mutant (R53H)FH1-4 showed comparable C3b binding but reduced cofactor and decay-accelerating activities.
Mutant (R78G)FH1-4 exhibited poor C3b binding and severely compromised regulatory functions.
FH1-4(I62) showed slightly enhanced cofactor activity compared to FH1-4(V62).

Conclusions:

N-terminal FH mutations, not solely C-terminal ones, can predispose individuals to aHUS.
Impaired FH N-terminal functions, including C3b binding and cofactor activity, contribute to aHUS pathogenesis.
Deficiencies in various FH functional properties can underlie the development of aHUS.