- Cipriani, Valentina;
- Lorés-Motta, Laura;
- He, Fan;
- Fathalla, Dina;
- Tilakaratna, Viranga;
- McHarg, Selina;
- Bayatti, Nadhim;
- Acar, İlhan E;
- Hoyng, Carel B;
- Fauser, Sascha;
- Moore, Anthony T;
- Yates, John RW;
- de Jong, Eiko K;
- Morgan, B Paul;
- den Hollander, Anneke I;
- Bishop, Paul N;
- Clark, Simon J
Age-related macular degeneration (AMD) is a leading cause of blindness. Genetic variants at the chromosome 1q31.3 encompassing the complement factor H (CFH, FH) and CFH related genes (CFHR1-5) are major determinants of AMD susceptibility, but their molecular consequences remain unclear. Here we demonstrate that FHR-4 plays a prominent role in AMD pathogenesis. We show that systemic FHR-4 levels are elevated in AMD (P-value = 7.1 × 10-6), whereas no difference is seen for FH. Furthermore, FHR-4 accumulates in the choriocapillaris, Bruch's membrane and drusen, and can compete with FH/FHL-1 for C3b binding, preventing FI-mediated C3b cleavage. Critically, the protective allele of the strongest AMD-associated CFH locus variant rs10922109 has the highest association with reduced FHR-4 levels (P-value = 2.2 × 10-56), independently of the AMD-protective CFHR1-3 deletion, and even in those individuals that carry the high-risk allele of rs1061170 (Y402H). Our findings identify FHR-4 as a key molecular player contributing to complement dysregulation in AMD.