A genome-wide association study identifies key modulators of complement factor H binding to malondialdehyde-epitopes

Area of Science:

• Immunogenetics
• Complement system biology
• Molecular medicine

Background:

• Genetic variants in complement factor H (CFH) are linked to age-related macular degeneration (AMD) and other complementopathies.
• Impaired binding of CFH or its splice variant FHL-1 to self-ligands, such as malondialdehyde (MDA)-modified molecules, disrupts homeostasis and complement regulation.

Purpose of the Study:

• To conduct an unbiased genome-wide search for genetic variants affecting CFH binding to MDA.
• To elucidate the mechanistic basis and functional consequences of these variants on complement regulation.

Main Methods:

• Genome-wide association study in 1,830 individuals to identify variants modifying CFH/FHL-1 binding to MDA.
• In vitro characterization of the binding affinities of CFH, FHL-1, FHR1, and FHR3 to MDA-epitopes.
• Assessment of FHR1's effect on CFH cofactor activity on necrotic cells.

Main Results:

• The CFH variant rs1061170 and the deletion of CFHR3 and CFHR1 were identified as dominant variants affecting CFH/FHL-1 binding to MDA.
• FHR1 and FHR3 compete with CFH for MDA-epitope binding, with FHR1 exhibiting the highest affinity.
• FHR1 binding to necrotic cells inhibited CFH cofactor activity, leading to increased complement activation.

Conclusions:

• The deletion of CFHR3 and CFHR1 offers protection in AMD by modulating CFH-MDA interactions.
• Genetic variants within the CFH/CFHR3/CFHR1 locus are crucial for recognizing altered-self molecules in maintaining tissue homeostasis.