title: A novel, multiplexed targeted mass spectrometry assay for quantification of complement factor H (CFH) variants and CFH-related proteins 1-5 in human plasma.
abstract: Age-related macular degeneration (AMD) is a leading cause of visual loss among older adults. Two variants in the complement factor H (CFH) gene, Y402H and I62V, are strongly associated with risk of AMD. CFH is encoded in regulator of complement activation gene cluster in chromosome 1q32, which includes complement factor related (CFHR) proteins, CFHR1 to CFHR5, with high amino acid sequence homology to CFH. Our goal was to build a SRM assay to measure plasma concentrations of CFH variants Y402, H402, I62, and V62, and CFHR1-5. The final assay consisted of 24 peptides and 72 interference-free SRM transition ion pairs. Most peptides showed good linearity over 0.3-200 fmol/μL concentration range. Plasma concentrations of CFH variants and CFHR1-5 were measured using the SRM assay in 344 adults. Plasma CFH concentrations (mean, SE in μg/mL) by inferred genotype were: YY402, II62 (170.1, 31.4), YY402, VV62 (188.8, 38.5), HH402, VV62 (144.0, 37.0), HY402, VV62 (164.2, 42.3), YY402, IV62 (194.8, 36.8), HY402, IV62 (181.3, 44.7). Mean (SE) plasma concentrations of CFHR1-5 were 1.63 (0.04), 3.64 (1.20), 0.020 (0.001), 2.42 (0.18), and 5.49 (1.55) μg/mL, respectively. This SRM assay should facilitate the study of the role of systemic complement and risk of AMD.
authors.affiliation: Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: Pingbo
authors.initials: P
authors.lastname: Zhang
authors.affiliation: National Institute on Aging, National Institutes of Health, Baltimore, MD, USA.
authors.forename: Min
authors.initials: M
authors.lastname: Zhu
authors.affiliation: Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: Minghui
authors.initials: M
authors.lastname: Geng-Spyropoulos
authors.affiliation: National Institute on Aging, National Institutes of Health, Baltimore, MD, USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: Shardell
authors.affiliation: National Institute on Aging, National Institutes of Health, Baltimore, MD, USA.
authors.forename: Marta
authors.initials: M
authors.lastname: Gonzalez-Freire
authors.affiliation: Icelandic Heart Association, Reykjavik, Iceland.|Department of Medicine, University of Iceland, Reykjavik, Iceland.
authors.forename: Vilmundur
authors.initials: V
authors.lastname: Gudnason
authors.affiliation: Icelandic Heart Association, Reykjavik, Iceland.
authors.forename: Gudny
authors.initials: G
authors.lastname: Eiriksdottir
authors.affiliation: Department of Epidemiology, Harvard TH Chan School of Public Health, Boston, MA, USA.|Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT, USA.
authors.forename: Debra
authors.initials: D
authors.lastname: Schaumberg
authors.affiliation: Advanced Clinical BioSystems Research Institute, The Heart Institute and, Cedars-Sinai Medical Center, Los Angeles, CA, USA.
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Van Eyk
authors.affiliation: National Institute on Aging, National Institutes of Health, Baltimore, MD, USA.
authors.forename: Luigi
authors.initials: L
authors.lastname: Ferrucci
authors.affiliation: Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Semba
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D001798:Blood Proteins / Q000032:analysis*; D017242:Complement Factor H / Q000032:analysis / Q000235:genetics; D003165:Complement System Proteins / Q000032:analysis*; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*; D010455:Peptides / Q000737:chemistry; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D012015:Reference Standards; D053719:Tandem Mass Spectrometry
chemical_list: D001798:Blood Proteins; C493495:CFH protein, human; D010455:Peptides; D017242:Complement Factor H; D003165:Complement System Proteins
keywords: Age-related macular degeneration; Biomedicine; Complement factor H; Complement factor H-related proteins; Mass spectrometry; Selected reaction monitoring