Molecular Vision 2015; 21:285-292 <http://www.molvis.org/molvis/v21/285>
Received 13 May 2014 | Accepted 12 March 2015 | Published 15 March 2015

This Article

Download PDF

Citation (for Endnote)

Google Scholar

Articles by the Authors

Analysis of rare variants in the CFH gene in patients with the cuticular drusen subtype of age-related macular degeneration

Maheswara R. Duvvari,1,2 Nicole T.M. Saksens,1 Johannes P.H. van de Ven,1 Yvonne de Jong-Hesse,3 Tina Schick,4 Willy M. Nillesen,2 Sascha Fauser,4 Lies H. Hoefsloot,2,5 Carel B. Hoyng,1 Eiko K. de Jong,1,2 Anneke I. den Hollander1,2

1Department of Ophthalmology, Radboud University Medical Centre, Nijmegen, the Netherlands; 2Department of Human Genetics, Radboud University Medical Centre, Nijmegen, the Netherlands; 3Department of Ophthalmology, VU Medical Centre, Amsterdam, the Netherlands; 4Department of Ophthalmology, University Hospital of Cologne, Cologne, Germany; 5Department of Clinical Genetics, Erasmus Medical Centre, Rotterdam, the Netherlands

Correspondence to: Anneke I. den Hollander, Department of Ophthalmology 409, Radboud University Nijmegen Medical Centre, Phillips van Leydenlaan 15, 6525 GA Nijmegen, The Netherlands; Phone: 31-24-3610402; FAX: 31-24-3540522; email: Anneke.denHollander@radboudumc.nl

Abstract

Purpose: Age-related macular degeneration (AMD) and cuticular drusen (CD), a clinical subtype of AMD, have been linked to genetic variants in the complement factor H (CFH) gene. In this study, we aimed to investigate the frequency of rare variants in the CFH gene in 180 cases with CD. In addition, we aimed to determine the frequency of a previously reported rare, highly penetrant CFH variant (p.Arg1210Cys) in a Dutch-German non-CD-type AMD case-control cohort, and to describe the phenotype of patients carrying the p.Arg1210Cys variant.

Methods: Study subjects were selected from the European Genetic Database (EUGENDA), a joint AMD database of the Radboud University Medical Centre and the University Hospital of Cologne, and graded at the Cologne Image Reading Centre and Laboratory (CIRCL). Additionally, two CD cases were recruited from the VU Medical Centre in Amsterdam. The CFH gene was analyzed in 180 CD cases with Sanger sequencing. All identified variants were analyzed for potential damaging effects with prediction software tools Sorting Intolerant from Tolerant (SIFT) and Polymorphism Phenotyping (PolyPhen). In addition, we genotyped the p.Arg1210Cys variant in 813 non-CD type AMD cases and 1175 controls.

Results: Sequencing identified 11 rare, heterozygous missense variants, one frameshift variant, and one splice acceptor site variant in 16 CD cases. The p.Arg1210Cys variant was identified in two CD cases but was not identified in our Dutch-German non-CD-type AMD case-control cohort.

Conclusions: The present study identified the presence of rare variants in the CFH gene in 16 (8.8%) of 180 patients with the CD subtype of AMD. The carriers of rare CFH variants displayed a significantly earlier age at onset than non-carriers (p=0.016). The rare missense variant p.Arg1210Cys was identified in two CD cases, but was not detected in 813 non-CD type AMD cases or in the 1,175 controls of our Dutch-German cohort. The current study suggests that the p.Arg1210Cys variant may be restricted to a subset of patients with the CD subtype of AMD. Detailed clinical phenotyping, including fluorescein angiography, of patients with AMD carrying the p.Arg1210Cys variant in other cohorts is required to confirm this finding.

Introduction

Age-related macular degeneration (AMD, OMIM 603075) is the most common cause of vision loss and irreversible blindness among the elderly in the Western world [1]. A major hallmark of AMD is the appearance of drusen in the macula accompanied by loss of sharp and central vision with advancing disease [2]. Cuticular drusen (CD, OMIM 126700), also termed “basal laminar drusen” or “early adult-onset, grouped drusen,” is a clinical subtype of AMD, characterized by the fundoscopic findings of innumerable, small (25–75 µm), slightly raised, round drusen, scattered throughout the central and peripheral retina [3]. CD commonly appear in early adulthood, and are readily visualized with fluorescein angiography (FA). In more advanced stages, the large number of CD present as a typical “stars-in-the-sky” appearance in the early phases of the angiogram [4]. Approximately 10% of AMD cases display the CD phenotype [5].

The early age of onset and the clustering of the CD phenotype in families implies a large genetic contribution to the development of CD [5-8]. This is supported by the observation that heterozygous mutations in the complement factor H (CFH) gene (ID 3075; OMIM 134370) segregate with the CD phenotype in multiplex families [5,8]. Common variants in and near the CFH gene have been associated with CD and with AMD [6,7]. In addition, a rare, highly penetrant variant (p.Arg1210Cys) in the CFH gene has been associated with AMD [9,10]. However, the p.Arg1210Cys variant was not detected in an Icelandic cohort or in the Han Chinese population [11,12]. This suggests that the rare p.Arg1210Cys variant is not consistently associated with AMD among different populations.

In this study, we aimed to investigate the frequency of rare variants in the CFH gene in 180 cases with CD. In addition, we aimed to determine the frequency of the rare highly penetrant p.Arg1210Cys variant in a Dutch-German non-CD type AMD case-control cohort, and to describe the phenotype of patients carrying the p.Arg1210Cys variant.

Methods

EUGENDA Study

The study participants were recruited from the European Genetic Database (EUGENDA), a multicenter database consisting of subjects from the Nijmegen area, the Netherlands and the Cologne area, Germany (Table 1). In addition, two CD cases were recruited at the VU Medical Centre in Amsterdam. All subjects analyzed in this study are Dutch and German and are of Caucasian descent. All subjects underwent ophthalmological examinations, and AMD staging was performed by the Cologne Image Reading Centre and Laboratory (CIRCL). CD was classified as a symmetric distributed pattern in both eyes of at least 50 scattered, uniformly-sized, small (25–75 µm), and hyperfluorescent drusen on FA in each eye, with a minimum of 20 drusen located outside the Wisconsin age-related maculopathy grading template [6,13]. AMD was classified by the presence of at least 15 intermediate (63–124 μm) drusen or at least one large (≥125 μm) druse in the Early Treatment Diabetic Retinopathy Study (ETDRS) grid (intermediate AMD) or geographic atrophy or choroidal neovascularization secondary to AMD (advanced AMD). Control subjects were ≥65 years of age and did not display AMD, which includes subjects without drusen, with only small drusen (<63 µm) or with pigmentary abnormalities alone or combined with less than 10 small drusen. Early AMD cases with ≥10 small drusen and pigmentary abnormalities or 1–14 intermediate drusen were excluded. The participants’ age at onset was noted as the age at which first visual complaints were experienced.

The EUGENDA study was approved by the local research ethics committees (Commissie Mensgebonden Onderzoek Regio Arnhem-Nijmegen, the Netherlands, and the Ethics Committee of the University Hospital Cologne, Germany). Written informed consent was obtained from all participants, and the study was performed in accordance with the tenets of the Declaration of Helsinki. The study was adhered to the ARVO statement for the use of human subjects in ophthalmic and vision research.

Sequencing

Sanger sequencing of the CFH (NM_000186) gene was performed in 178 CD cases from the EUGENDA database and two CD cases from Amsterdam. Primers were designed to amplify all 22 exons and flanking intron-exon junctions with Primer3 software (Appendix 1). PCR were performed, and amplification products were sequenced using an automated sequencer (BigDye Terminator, version 3, 3730 DNA analyzer; Applied Biosystems, Waltham, MA). All sequencing chromatograms were compared to the reference sequence using ContigExpress (Vector NTI Advance, Version 11.0, Life Technologies, Waltham, MA). Each newly identified variant was confirmed with a second independent PCR and bidirectional Sanger sequencing. All identified variants were annotated based on the Human Genome Variation Society (HGVS) nomenclature. Variants with a minor allele frequency (MAF) <1% were considered rare variants. The number of carriers of rare variants discovered in the CD cohort (n=180) was compared to the general population (n=4300) using data from Exome Variant Server (EVS). Rare coding (missense, frameshift, and nonsense) and splice site variants in the CFH gene were used in the analysis. The average age at onset of the patients with CD were compared in carriers of rare CFH variants (n=16; age at onset known=13) versus non-carriers of rare CFH variants (n=164; age at onset known=64). The predicted effects of identified missense variants were examined using Polymorphism Phenotyping (PolyPhen) and Sorting Intolerant from Tolerant (SIFT) [14,15].

Genotyping

The CFH p.Arg1210Cys variant was genotyped in 813 non-CD type AMD cases and 1,175 controls from the EUGENDA database using a competitive allele-specific PCR assay (KASPar SNP Genotyping System, KBiosciences, Teddington, UK). KASPar genotyping was performed according to the manufacturer’s protocol in a volume of 4 µl containing 10 ng of genomic DNA, 2.5 µl of 2X reaction mix, and 0.069 µl of assay (Appendix 2). Thermal cycling conditions included a preincubation step at 94 °C for 15 min, 20 cycles of 94 °C for 10 s, 57 °C for 5 s, 72 °C for 10 s, followed by 23 cycles of 94 °C for 10 s, 57 °C for 20 s, 72 °C for 40 s. Plates were analyzed on a 7900 Fast Real-Time PCR system (Applied Biosystems).

Results

Through sequencing of the exons and flanking intron-exon boundaries of the CFH gene in 180 unrelated CD cases, 13 heterozygous rare variants in 16 cases (8.8%) were identified (Table 2). Of these 13 variants, 11 were missense variants, one was a frameshift variant (p.Ala301Asnfs*25), and one was a splice acceptor site variant (c.428–2A>G). Seven variants (c.428–2A>G, p.Ala161Ser, p.Ala173Gly, p.Arg175Gln, p.Ser193Leu, p.Ala301Asnfs*25, and p.Trp379Arg) were not present in public genetic variant databases (dbSNP, ESP6500/EVS) and therefore represent rare, unique variants. Six variants (p.Leu3Val / rs139254423, p.Ile216Thr/rs183474263, p.Gln400Lys/rs201671665, p.Gln950His/rs149474608, p.Thr956Met/rs145975787, and p.Arg1210Cys/rs121913059) had low reported MAFs in these databases (MAFs<0.001). The total number of carriers of rare CFH variants in the patients with CD (16 (8.8%) of 180) is significantly higher than the total number of carriers of rare CFH variants in the general population (185 (4.3%) of 4300; p=0.008, Fisher’s test). The mean age at onset in carriers of rare CFH variants (57.2±16.8 years) is significantly earlier than non-carriers of rare CFH variants (66.1±10.8 years; p=0.016, Student t test). Using the online prediction algorithms SIFT and PolyPhen, potential damaging effects of the missense variants were assessed. Three missense variants (p.Ser193Leu, p.Trp379Arg and p.Gln950His) showed a consistent deleterious and damaging score by both PolyPhen and SIFT, while three variants were predicted deleterious or damaging by one of the prediction algorithms. Five missense variants were not predicted to be deleterious or damaging by either algorithm, including the p.Arg1210Cys variant.

The p.Arg1210Cys variant was identified in two unrelated individuals with CD. To test for a possible association of the p.Arg1210Cys variant in our Dutch-German non-CD type AMD case-control cohort, we genotyped this variant in 813 cases and 1175 controls from the EUGENDA database (Table 1). The p.Arg1210Cys variant was not found in our genotyped cohort, except in the two patients with CD in whom the p.Arg1210Cys variant was identified with sequence analysis of the CFH gene.

Both individuals carrying the p.Arg1210Cys variant presented with hyperfluorescent drusen on FA, typical of the CD subtype of AMD (Figure 1). In case 1, drusen were first noted at 50 years, with both eyes displaying numerous small drusen in the posterior pole and the peripheral retina (Figure 1A–D). Case 2 had onset of visual impairment at 64 years and presented with numerous small drusen in the posterior pole in both eyes. Furthermore, case 2 displayed a large fibrotic scar in the right eye (Figure 1E,G), pigmentary changes, and an occult choroidal neovascularization in the left eye (Figure 1F,H).

Discussion

The present study identified the presence of rare variants (MAF<1%) in the CFH gene in 16 (8.8%) of 180 patients diagnosed with the CD subtype of AMD. This number is significantly higher than the number of carriers of rare CFH variants in the general population (4.3%, p=0.008). This study showed that carriers of rare CFH variants display an earlier age at onset than non-carriers of rare CFH variants (p=0.016). The rare missense variant p.Arg1210Cys was identified in two CD cases, but was not detected in the 813 non-CD-type AMD cases and 1,175 controls of our Dutch-German cohort. The p.Arg1210Cys variant was previously found to be highly associated with AMD in North American cohorts, with a frequency in patients with AMD of 40/2,423 (1.65%) [10] and 23/2,335 (0.99%) [9], respectively. However, the p.Arg1210Cys variant was not detected in an Icelandic cohort (consisting of 1,143 patients with AMD) or in a Han Chinese cohort (consisting of 258 patients with AMD) [11,12].

The current study suggests that the p.Arg1210Cys variant may be restricted to a subset of patients with AMD with CD. Since the cohort of patients with CD analyzed in our study was too small to reliably test for an association, this finding must be confirmed in additional cohorts of patients with CD, and/or by detailed clinical phenotyping of patients with AMD carrying the p.Arg1210Cys variant using FA. An under- or overrepresentation of patients with AMD with CD-like characteristics between cohorts might explain the discrepancy in the p.Arg1210Cys association observed among the North American [10], Icelandic [11], Han Chinese [12], and Dutch-German cohorts. However, the distribution of low-frequency alleles vary among populations, since they tend to be the result of recent mutations and are expected to geographically cluster around the location at which the mutation first arose [16]. The frequency of disease-causing variants can differ significantly among populations [17] or can even be restricted to a geographic region [18].

The CFH protein is an important regulator of the alternative pathway of the complement cascade that plays a key role in the clearance of pathogens and immune complexes, and modulates adaptive immunity [19]. CFH is composed of 20 sequential complement control protein (CCP) domains (Figure 2). Five of the identified rare variants (p.Ala161Ser, p.Ala173Gly, p.Arg175Gln, p.Ser193Leu, and p.Ile216Thr) are clustered within the N-terminal domains CCPs 1–4. This region has been demonstrated to be involved in cofactor activity [20], suggesting that these variants potentially have an impact on CFH cofactor activity. Two variants, p.Trp379Arg and p.Gln400Lys, are located within the CCP6 and CCP7 domains, respectively, close to the common p.Tyr402His [21] AMD risk variant, which causes defective heparin-binding properties [20]. This raises the possibility that these variants may exert a similar effect. Three variants (p.Gln950His, p.Thr956Met, and p.Arg1210Cys) are clustered in the C-terminal CCP domains 16–20. Functional studies have demonstrated that these four C-terminal CCP domains are necessary for the host cell recognition or discrimination properties of CFH [22]. In addition, we identified one frameshift (p.Ala301Asnfs*25) variant and one splice-acceptor site (428–2A>G) variant, which are predicted to abolish CFH function.

Notably, not all missense variants identified in this study were predicted by SIFT and PolyPhen to be pathogenic. In particular, this is the case for the p.Arg1210Cys variant, which was not predicted to be deleterious or damaging by either algorithm. However, functional studies have demonstrated that the p.Arg1210Cys variant compromises CFH function, as the mutant protein exhibits defective binding to C3d, C3b, heparin, and endothelial cells, and forms a covalent interaction with human serum albumin [10,23-26]. Therefore, although prediction software tools such as SIFT and PolyPhen may assist in assessing potential damaging rare variants, functional validation of CFH mutant proteins is needed to properly assess the functional consequence of these genetic variations.

The majority of the identified variants were not present in public databases and have not been previously linked to other diseases, demonstrating that many CFH variants are novel and unique for individual patients. The number of carriers of rare variants is significantly higher in patients with CD than the number of carriers in the general population (EVS; p=0.008). The carriers of rare CFH variants displayed an earlier age at onset than non-carriers (p=0.016). This emphasizes the importance of a sequence analysis of the entire CFH coding region and the splice junction of the CFH gene to identify the causative allele, in particular in individuals with the CD subtype of AMD. The p.Arg1210Cys variant has previously been demonstrated to confer a high risk of developing AMD [10], underscoring its pathogenicity. However, two CFH variants were recently identified in a large scale sequencing study, and were found not to be associated with the disease: p.Glu950His was identified in 9/3,343 patients with AMD and 10/1,480 controls (p=0.98), p.Thr956Met was identified in 4/3,348 patients with AMD and 6/1,484 controls (p=0.99) [27]. This implies that these alleles may not be causative for AMD. Four of the identified variants (p.Gln400Lys, p.Gln950His, p.Thr956Met, and p.Arg1210Cys) were previously reported in patients with atypical hemolytic uremic syndrome (aHUS), a devastating renal disease, supporting a previously proposed theory that an allelic overlap exists between two distinct pathologies, AMD and aHUS [28-30]. Patients with CD carrying aHUS mutations did not have renal complaints at the time of recruitment (Appendix 3). This suggests that additional genetic variants and/or external triggers determine the disease outcome in individuals carrying these alleles.

In conclusion, the present study identified the presence of rare variants in the CFH gene in 16 (8.8%) of 180 patients with the CD subtype of AMD. The carriers of rare CFH variants displayed an earlier age at onset than non-carriers (p=0.016). A previously reported rare missense variant, p.Arg1210Cys, was identified in two CD cases, but was not detected in the 813 non-CD type AMD cases and 1,175 controls of our Dutch-German cohort. The current study suggests that the p.Arg1210Cys variant may be restricted to a subset of patients with the CD subtype of AMD. Detailed clinical phenotyping, including fluorescein angiography, of patients with AMD carrying the p.Arg1210Cys variant in other cohorts is required to confirm this finding.

Appendix 1: List of CFH gene sequencing primers.

Appendix 2: Arg1210Cys variant KASPar primers.

Appendix 3: Clinical description of CD patients with rare variants in the CFH gene.

Acknowledgments

This study was supported by Netherlands Organization for Scientific Research (Vidi Innovational Research Award 016096309 to A.I.d.H.) and the Foundation Fighting Blindness USA (grant CGE08110548RAD04 to A.I.d.H.).

References

  1. Klaver CCW, Wolfs RC, Vingerling JR, Hofman A, de Jong PT. Age-specific prevalence and causes of blindness and visual impairment in an older population: the Rotterdam Study. Arch Ophthalmol. 1998; 116:653-8. [PMID: 9596502]
  2. de Jong PT. Age-related macular degeneration. N Engl J Med. 2006; 355:1474-85. [PMID: 17021323]
  3. Boon CJF, van de Ven JPH, Hoyng CB, den Hollander AI, Klevering BJ. Cuticular drusen: stars in the sky. Prog Retin Eye Res. 2013; 37:90-113. [PMID: 24028794]
  4. Guigui B, Leveziel N, Martinet V, Massamba N, Sterkers M, Coscas G, Souied EH. Angiography features of early onset drusen. Br J Ophthalmol. 2011; 95:238-44. [PMID: 20610475]
  5. van de Ven JPH, Boon CJF, Fauser S, Hoefsloot LH, Smailhodzic D, Schoenmaker-Koller FE, Klevering BJ, Klaver CCW, den Hollander AI, Hoyng CB. Clinical evaluation of 3 families with basal laminar drusen caused by novel mutations in the complement factor H gene. Arch Ophthalmol. 2012; 130:1038-47. [PMID: 22491393]
  6. van de Ven JPH, Smailhodzic D, Boon CJF, Fauser S, Groenewoud JM, Chong NV, Hoyng CB, Klevering BJ, den Hollander AI. Association analysis of genetic and environmental risk factors in the cuticular drusen subtype of age-related macular degeneration. Mol Vis. 2012; 18:2271-8. [PMID: 22933840]
  7. Grassi MA, Folk JC, Scheetz TE, Taylor CM, Sheffield VC, Stone EM. Complement factor H polymorphism p.Tyr402His and cuticular Drusen. Arch Ophthalmol. 2007; 125:93-7. [PMID: 17210858]
  8. Boon CJF, Klevering BJ, Hoyng CB, Zonneveld-Vrieling MN, Nabuurs SB, Blokland E, Cremers FP, den Hollander AI. Basal laminar drusen caused by compound heterozygous variants in the CFH gene. Am J Hum Genet. 2008; 82:516-23. [PMID: 18252232]
  9. Zhan X, Larson DE, Wang C, Koboldt DC, Sergeev YV, Fulton RS, Fulton LL, Fronick CC, Branham KE, Bragg-Gresham J, Jun G, Hu Y, Kang HM, Liu D, Othman M, Brooks M, Ratnapriya R, Boleda A, Grassmann F, von Strachwitz C, Olson LM, Buitendijk GH, Hofman A, van Duijn CM, Cipriani V, Moore AT, Shahid H, Jiang Y, Conley YP, Morgan DJ, Kim IK, Johnson MP, Cantsilieris S, Richardson AJ, Guymer RH, Luo H, Ouyang H, Licht C, Pluthero FG, Zhang MM, Zhang K, Baird PN, Blangero J, Klein ML, Farrer LA, DeAngelis MM, Weeks DE, Gorin MB, Yates JR, Klaver CC, Pericak-Vance MA, Haines JL, Weber BH, Wilson RK, Heckenlively JR, Chew EY, Stambolian D, Mardis ER, Swaroop A, Abecasis GR. Identification of a rare coding variant in complement 3 associated with age-related macular degeneration. Nat Genet. 2013; 45:1375-9. [PMID: 24036949]
  10. Raychaudhuri S, Iartchouk O, Chin K, Tan PL, Tai AK, Ripke S, Gowrisankar S, Vemuri S, Montgomery K, Yu Y, Reynolds R, Zack DJ, Campochiaro B, Campochiaro P, Katsanis N, Daly MJ, Seddon JM. A rare penetrant mutation in CFH confers high risk of age-related macular degeneration. Nat Genet. 2011; 43:1232-6. [PMID: 22019782]
  11. Helgason H, Sulem P, Duvvari MR, Luo H, Thorleifsson G, Stefansson H, Jonsdottir I, Masson G, Gudbjartsson DF, Walters GB, Magnusson OT, Kong A, Rafnar T, Kiemeney LA, Schoenmaker-Koller FE, Zhao L, Boon CJ, Song Y, Fauser S, Pei M, Ristau T, Patel S, Liakopoulos S, van de Ven JPH, Hoyng CB, Ferreyra H, Duan Y, Bernstein PS, Geirsdottir A, Helgadottir G, Stefansson E, den Hollander AI, Zhang K, Jonasson F, Sigurdsson H, Thorsteinsdottir U, Stefansson K. A rare nonsynonymous sequence variant in C3 is associated with high risk of age-related macular degeneration. Nat Genet. 2013; 45:1371-4. [PMID: 24036950]
  12. Shen SK, Liu XQ, Lu F, Yang ZL, Shi Y. Association study between age-related macular degeneration and R1210C mutation of CFH gene in Chinese population. Chin J Med Genet. 2012; 29:570-2. [PMID: 23042396]
  13. Klein R, Davis MD, Magli YL, Segal P, Klein BE, Hubbard L. The Wisconsin age-related maculopathy grading system. Ophthalmology. 1991; 98:1128-34. [PMID: 1843453]
  14. Adzhubei I, Jordan DM, Sunyaev SR. Predicting functional effect of human missense mutations using PolyPhen-2. Curr Protoc Hum Genet. 2013; 76:7201-41. [PMID: 23315928]
  15. Kumar P, Henikoff S, Ng PC. Predicting the effects of coding non-synonymous variants on protein function using the SIFT algorithm. Nat Protoc. 2009; 4:1073-81. [PMID: 19561590]
  16. Novembre J, Johnson T, Bryc K, Kutalik Z, Boyko AR, Auton A, Indap A, King KS, Bergmann S, Nelson MR, Stephens M, Bustamante CD. Genes mirror geography within Europe. Nature. 2008; 456:98-101. [PMID: 18758442]
  17. Maugeri A, Flothmann K, Hemmrich N, Ingvast S, Jorge P, Paloma E, Patel R, Rozet JM, Tammur J, Testa F, Balcells S, Bird AC, Brunner HG, Hoyng CB, Metspalu A, Simonelli F, Allikmets R, Bhattacharya SS, D'Urso M, Gonzalez-Duarte R, Kaplan J, te Meerman GJ, Santos R, Schwartz M, Van Camp G, Wadelius C, Weber BH, Cremers FP. The ABCA4 2588G>C Stargardt mutation: single origin and increasing frequency from South-West to North-East Europe. Eur J Hum Genet. 2002; 10:197-203. [PMID: 11973624]
  18. Mukhopadhyay A, Nikopoulos K, Maugeri A, de Brouwer AP, van Nouhuys CE, Boon CJF, Perveen R, Zegers HA, Wittebol-Post D, van den Biesen PR, van der Velde-Visser SD, Brunner HG, Black GC, Hoyng CB, Cremers FP. Erosive vitreoretinopathy and wagner disease are caused by intronic mutations in CSPG2/Versican that result in an imbalance of splice variants. Invest Ophthalmol Vis Sci. 2006; 47:3565-72. [PMID: 16877430]
  19. Walport MJ. Complement. First of two parts. N Engl J Med. 2001; 344:1058-66. [PMID: 11287977]
  20. Clark SJ, Higman VA, Mulloy B, Perkins SJ, Lea SM, Sim RB, Day AJ. His-384 allotypic variant of factor H associated with age-related macular degeneration has different heparin binding properties from the non-disease-associated form. J Biol Chem. 2006; 281:24713-20. [PMID: 16787919]
  21. Haines JL, Hauser MA, Schmidt S, Scott WK, Olson LM, Gallins P, Spencer KL, Kwan SY, Noureddine M, Gilbert JR, Schnetz-Boutaud N, Agarwal A, Postel EA, Pericak-Vance MA. Complement factor H variant increases the risk of age-related macular degeneration. Science. 2005; 308:419-21. [PMID: 15761120]
  22. Pickering MC, de Jorge EG, Martinez-Barricarte R, Recalde S, Garcia-Layana A, Rose KL, Moss J, Walport MJ, Cook HT. de C, Sr., Botto M. Spontaneous hemolytic uremic syndrome triggered by complement factor H lacking surface recognition domains. J Exp Med. 2007; 204:1249-56. [PMID: 17517971]
  23. Sánchez-Corral P, Perez-Caballero D, Huarte O, Simckes AM, Goicoechea E, Lopez-Trascasa M, de Cordoba SR. Structural and functional characterization of factor H mutations associated with atypical hemolytic uremic syndrome. Am J Hum Genet. 2002; 71:1285-95. [PMID: 12424708]
  24. Manuelian T, Hellwage J, Meri S, Caprioli J, Noris M, Heinen S, Jozsi M, Neumann HP, Remuzzi G, Zipfel PF. Mutations in factor H reduce binding affinity to C3b and heparin and surface attachment to endothelial cells in hemolytic uremic syndrome. J Clin Invest. 2003; 111:1181-90. [PMID: 12697737]
  25. Józsi M, Heinen S, Hartmann A, Ostrowicz CW, Halbich S, Richter H, Kunert A, Licht C, Saunders RE, Perkins SJ, Zipfel PF, Skerka C. Factor H and atypical hemolytic uremic syndrome: mutations in the C-terminus cause structural changes and defective recognition functions. J Am Soc Nephrol. 2006; 17:170-7. [PMID: 16338962]
  26. Ferreira VP, Herbert AP, Cortes C, McKee KA, Blaum BS, Esswein ST, Uhrin D, Barlow PN, Pangburn MK, Kavanagh D. The binding of factor H to a complex of physiological polyanions and C3b on cells is impaired in atypical hemolytic uremic syndrome. J Immunol. 2009; 182:7009-18. [PMID: 19454698]
  27. Seddon JM, Yu Y, Miller EC, Reynolds R, Tan PL, Gowrisankar S, Goldstein JI, Triebwasser M, Anderson HE, Zerbib J, Kavanagh D, Souied E, Katsanis N, Daly MJ, Atkinson JP, Raychaudhuri S. Rare variants in CFI, C3 and C9 are associated with high risk of advanced age-related macular degeneration. Nat Genet. 2013; 45:1366-70. [PMID: 24036952]
  28. Caprioli J, Castelletti F, Bucchioni S, Bettinaglio P, Bresin E, Pianetti G, Gamba S, Brioschi S, Daina E, Remuzzi G, Noris M. Complement factor H mutations and gene polymorphisms in haemolytic uraemic syndrome: the C-257T, the A2089G and the G2881T polymorphisms are strongly associated with the disease. Hum Mol Genet. 2003; 12:3385-95. [PMID: 14583443]
  29. Dragon-Durey MA, Fremeaux-Bacchi V, Loirat C, Blouin J, Niaudet P, Deschenes G, Coppo P, Herman FW, Weiss L. Heterozygous and homozygous factor h deficiencies associated with hemolytic uremic syndrome or membranoproliferative glomerulonephritis: report and genetic analysis of 16 cases. J Am Soc Nephrol. 2004; 15:787-95. [PMID: 14978182]
  30. Pérez-Caballero D, Gonzalez-Rubio C, Gallardo ME, Vera M, Lopez-Trascasa M. Rodriguez de CS, Sanchez-Corral P. Clustering of missense mutations in the C-terminal region of factor H in atypical hemolytic uremic syndrome. Am J Hum Genet. 2001; 68:478-84. [PMID: 11170895]