June 2022
Volume 63, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2022
Relative abundance of FH and FHR-4 in genotyped human donor eyes: significance for AMD pathogenesis
Author Affiliations & Notes
  • Kelly Mulfaul
    University of Iowa Institute for Vision Research, Iowa, United States
    Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa, United States
  • Malia M Collins
    University of Iowa Institute for Vision Research, Iowa, United States
    Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa, United States
  • Louisa M Affatigato
    University of Iowa Institute for Vision Research, Iowa, United States
    Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa, United States
  • Edwin M Stone
    University of Iowa Institute for Vision Research, Iowa, United States
    Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa, United States
  • Budd A. Tucker
    University of Iowa Institute for Vision Research, Iowa, United States
    Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa, United States
  • Robert F Mullins
    University of Iowa Institute for Vision Research, Iowa, United States
    Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa, United States
  • Footnotes
    Commercial Relationships   Kelly Mulfaul None; Malia Collins None; Louisa Affatigato None; Edwin Stone None; Budd Tucker None; Robert Mullins None
  • Footnotes
    Support  Fight for Sight PD 20005, NIH EY024605, EY025580 and EY029838, the Elmer and Sylvia Sramek Charitable Trust, and The Edward N. & Della L. Thome Memorial Foundation.
Investigative Ophthalmology & Visual Science June 2022, Vol.63, 4615 – F0407. doi:
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    • Get Citation

      Kelly Mulfaul, Malia M Collins, Louisa M Affatigato, Edwin M Stone, Budd A. Tucker, Robert F Mullins; Relative abundance of FH and FHR-4 in genotyped human donor eyes: significance for AMD pathogenesis. Invest. Ophthalmol. Vis. Sci. 2022;63(7):4615 – F0407.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Age-related macular degeneration (AMD) is a leading cause of vision loss globally. A single nucleotide polymorphism Y402H in Complement factor H, a key negative regulator of complement activation, has been shown to increase an individual’s risk of developing AMD. The CFH gene is located on chromosome 1 in the regulator of complement activation gene cluster. Factor H related proteins 1-5 are encoded downstream of CFH. In contrast to FH, FHR-4 acts to promote complement activation and has been suggested to compete with FH for ligand binding. Recently FHR-4 levels have been shown to be elevated systemically in the plasma and serum of AMD patients, however the abundance of FHR-4 protein in RPE choroid tissue from genotyped AMD donors and age-matched controls has not been assessed.

Methods : We studied FH and FHR-4 protein expression in genotyped human donor eyes by both western blot and immunohistochemistry. Western blots were performed on serially extracted aqueous soluble (circulating) and detergent soluble (tissue bound) protein fractions from 2 YY control, 2 YY AMD, 2 HH control and 2 HH AMD donors. Macular tissue sections from 4 YY control, 4 YY AMD, 3 HH control and 3 HH AMD donors were incubated with goat-anti-FH and mouse anti-FHR-4 antibodies.

Results : We found that serum FH protein levels were similar in all donors whereas FHR-4 was elevated in AMD donor serum, consistent with previous reports. We next assessed the relative abundance of FH and FHR-4 in choroid and detected FH protein in both soluble and insoluble RPE/choroid fractions, whereas low levels of FHR-4 were observed only in the soluble fraction. Immunohistochemically we observed robust labeling for FH in all samples, most notably in extracellular domains surrounding the choriocapillaris. In contrast, labeling for FHR-4 protein was variable and relatively weak.

Conclusions : Individuals homozygous for Y402H polymorphism who have increased risk of developing AMD have elevated levels of FHR-4 in their serum, however, no alterations are observed in the local choroidal concentrations of FHR-4. FH, but not FHR4, was found in the detergent soluble, ECM bound protein fraction. Thus, FH is the most abundant member of the FH/FHR family in the choroid, highlighting its importance in AMD pathogenesis.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

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