CFHR4 and age-related macular degeneration: However, because this variant is in high linkage disequilibrium (LD) with several common single nucleotide polymorphisms (SNP) within the Chr1 AMD locus (r2 > 0.8), its effect on complement activation could not be conclusively linked solely to CFHR4. Even though CFHR4 mRNA is not expressed in ocular tissue, FHR-4 protein has been detected in Bruch’s membrane and between capillaries of the choriocapillaris43.