• Beyond factor H: The impact of genetic-risk variants for age-related macular degeneration on circulating factor-H-like 1 and factor-H-related protein concentrations.

      Cipriani, Valentina; email: v.cipriani@qmul.ac.uk; Tierney, Anna; Griffiths, John R; Zuber, Verena; Sergouniotis, Panagiotis I; Yates, John R W; Moore, Anthony T; Bishop, Paul N; Clark, Simon J; Unwin, Richard D; email: r.unwin@manchester.ac.uk (2021-07-12)
      Age-related macular degeneration (AMD) is a leading cause of vision loss; there is strong genetic susceptibility at the complement factor H (CFH) locus. This locus encodes a series of complement regulators: factor H (FH), a splice variant factor-H-like 1 (FHL-1), and five factor-H-related proteins (FHR-1 to FHR-5), all involved in the regulation of complement factor C3b turnover. Little is known about how AMD-associated variants at this locus might influence FHL-1 and FHR protein concentrations. We have used a bespoke targeted mass-spectrometry assay to measure the circulating concentrations of all seven complement regulators and demonstrated elevated concentrations in 352 advanced AMD-affected individuals for all FHR proteins (FHR-1, p = 2.4 × 10 ; FHR-2, p = 6.0 × 10 ; FHR-3, p = 1.5 × 10 ; FHR-4, p = 1.3 × 10 ; FHR-5, p = 1.9 × 10 ) and FHL-1 (p = 4.9 × 10 ) when these individuals were compared to 252 controls, whereas no difference was seen for FH (p = 0.94). Genome-wide association analyses in controls revealed genome-wide-significant signals at the CFH locus for all five FHR proteins, and univariate Mendelian-randomization analyses strongly supported the association of FHR-1, FHR-2, FHR-4, and FHR-5 with AMD susceptibility. These findings provide a strong biochemical explanation for how genetically driven alterations in circulating FHR proteins could be major drivers of AMD and highlight the need for research into FHR protein modulation as a viable therapeutic avenue for AMD. [Abstract copyright: Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.]