Translational Mini-Review Series on Complement Factor H: Genetics and disease associations of human complement factor H

Abstract

OTHER ARTICLES PUBLISHED IN THIS TRANSLATIONAL MINI-REVIEW SERIES ON COMPLEMENT FACTOR H
Structural and functional correlations for factor H. Clin Exp Immunol 2008; 151: doi:10.1111/j.1365-2249.2007.03553.x
Therapies of renal diseases associated with complement factor H abnormalities: atypical haemolytic uraemic syndrome and membranoproliferative glomerulonephritis. Clin Exp Immunol 2008; 151: doi:10.1111/j.1365-2249.2007.03558.x
Renal diseases associated with complement factor H: novel insights from humans and animals. Clin Exp Immunol 2008; 151: doi:10.1111/j.1365-2249.2007.03574.x
Factor H is an abundant plasma glycoprotein that plays a critical role in the regulation of the complement system in plasma and in the protection of host cells and tissues from damage by complement activation. Several recent studies have described the association of genetic variations of the complement factor H gene (CFH) with atypical haemolytic uraemic syndrome (aHUS), age-related macular degeneration (AMD) and membranoproliferative glomerulonephritis (MPGN). This review summarizes our current knowledge of CFH genetics and examines the CFH genotype–phenotype correlations that are helping to understand the molecular basis underlying these renal and ocular pathologies.

Full text

Translational Mini-Review Series on Complement Factor H:
Genetics and disease associations of human complement factor H
OTHER ARTICLES PUBLISHED IN THIS TRANSLATIONAL MINI-REVIEW SERIE S ON COMPLEMENT FACTOR H
Structural and functional correlations for factor H. Clin Exp Immunol 2008; 151: doi:10.1111/j.1365-2249.2007.03553.x
Therapies of renal diseases associated with complement factor H abnormalities: atypical haemolytic uraemic syndrome and membranoproliferative
glomerulonephritis. Clin Exp Immunol 2008; 151: doi:10.1111/j.1365-2249.2007.03558.x
Renal diseases associated with complement factor H: novel insights from humans and animals. Clin Exp Immunol 2008; 151:
doi:10.1111/j.1365-2249.2007.03574.x
S. Rodríguez de Córdoba and
E. Goicoechea de Jorge
Centro de Investigaciones Biológicas and Centro
de Investigación Biomédica en Red de
Enfermedades Raras, Madrid, Spain
Summary
Factor H is an abundant plasma glycoprotein that plays a critical role in the
regulation of the complement system in plasma and in the protection of host
cells and tissues from damage by complement activation. Several recent
studies have described the association of genetic variations of the complement
factorHgene(CFH) with atypical haemolytic uraemic syndrome (aHUS),
age-related macular degeneration (AMD) and membranoproliferative glom-
erulonephritis (MPGN). This review summarizes our current knowledge of
CFH genetics and examines the CFH genotype–phenotype correlations that
are helping to understand the molecular basis underlying these renal and
ocular pathologies.
Keywords: age-related macular degeneration (AMD),factor H,haemolytic–
uraemic syndrome (HUS),membranoproliferative glomerulonephritis type II
(MPGN2),RCA
Accepted for publication 16 October 2007
Correspondence: S. R. de Córdoba, Centro de
Investigaciones Biológicas, Ramiro de Maeztu 9,
28040 Madrid, Spain.
E-mail: SRdeCordoba@cib.csic.es
Complement activation and regulation
Complement is a major component of innate immunity,
with crucial roles in microbial killing, apoptotic cell clear-
ance and immune complex handling. Activation of comple-
ment by foreign surfaces (alternative pathway; AP), antibody
(classical pathway; CP) or mannan (lectin pathway; LP)
causes target opsonization, leucocyte recruitment and
cell lysis. The critical steps in complement activation are
the formation of unstable protease complexes, named
C3-convertases (AP, C3bBb; CP/LP, C2aC4b) and the cleav-
age of C3 to generate C3b. Convertase-generated C3b can
form more AP C3-convertase, providing exponential ampli-
fication to the initial activation. Binding of C3b to the
C3-convertases generates the C5-convertases with the capac-
ity to bind and cleave C5, initiating formation of the lytic
membrane attack complex (MAC).
Nascent C3b binds indiscriminately to pathogens and
adjacent host cells. To prevent damage to self and to avoid
wasteful consumption of components, complement is
under the control of multiple regulatory proteins that limit
complement activation, either by inactivating C3b or C4b,
by dissociating the C3/C5 convertases or by inhibiting the
MAC formation. In health, activation of C3 in the blood
is kept at a low level and deposition of C3b and further
activation of complement is limited to the surface of
pathogens [1].
Complement regulation by factor H
Factor H is a relatively abundant plasma protein that is
essential to maintain complement homeostasis and to
restrict the action of complement to activating surfaces.
Factor H binds to C3b, accelerates the decay of the alterna-
tive pathway C3-convertase (C3bBb) and acts as a co-factor
for the factor I-mediated proteolytic inactivation of C3b
[2–4]. Factor H regulates complement both in fluid phase
and on cellular surfaces. However, while factor H binds and
inactivates C3b promptly in fluid phase, the inactivation of
surface-bound C3b by factor H is dependent on the chemical
composition of the surface to which C3b is bound. In the
presence of polyanions such as sialic acids, glycosaminogly-
cans or sulphated polysaccharides (heparins), the affinity of
factor H for surface-bound C3b increases as a consequence
TRANSLATIONAL MINI-REVIEW SERIES ON COMPLEMENT FACTOR H
Guest Editor: Marina Botto
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Clinical and Experimental Immunology
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Journal compilation © 2008 British Society for Immunology, Clinical and Experimental Immunology,151: 1–13

of the simultaneous recognition of both polyanionic mol-
ecules and bound C3b by the same factor H molecule [5–7].
Factor H and factor H-related proteins
Factor H is a single polypeptide chain glycoprotein
(155 kDa; e=1·95 M-1cm-1)composedof20repetitive
units of 60 amino acids [8], named short consensus repeats
(SCR) or complement control protein modules (CCP),
arranged in a continuous fashion. The factor H molecule
includes different interaction sites for C3b and polyanions
which delineate distinct functional domains at the N- and
C-termini (Fig. 1). The C3b binding site in SCR1-4 is the
only site essential for the factor I co-factor activity of factor
H. Similarly, the C3b/polyanions-binding site located within
SCR19–20 is the most important site for preventing alterna-
tive pathway activation on host cells (reviewed in [21]).
Factor H is produced constitutively by the liver [22,23] and is
found in human plasma at concentrations of 116–562 mg/ml
[24]. Extrahepatic synthesis of factor H also occurs in a wide
variety of cell types, such as retinal pigment epithelial cells,
peripheral blood lymphocytes, myoblasts, rhabdomyosar-
coma cells, fibroblasts,umbilical vein endothelial cells, glom-
erular mesangial cells, neurones, glia cells, etc. [25–27]. The
extrahepatic production of factor H is interpreted as a
mechanism to increase the local concentration, which could
be advantageous for the protection of host cells from
complement activation in sites of infection or inflammation.
In human plasma there are six proteins that are structur-
ally related and cross-react immunochemically with factor
H. FHL-1 is the product of the alternative splicing of the
gene encoding factor H (CFH) [9,23,28–30]. In addition, five
proteins related to factor H are encoded by the five genes
CFHR1,CFHR2,CFHR3,CFHR4 and CFHR5 linked closely
to CFH [31–34]. These proteins are also probably synthe-
sized in the liver, but their concentrations are much lower
than that of factor H. The functional properties of CFHR1,
-2, -3, -4 and -5 are not defined fully. They are all composed
of SCRs with different degrees of identity with SCRs in factor
H [33–37].
The CFH gene
CFH is a member of the regulator of complement activation
(RCA) gene cluster on chromosome 1q32 (Fig. 2) [21,39].
CFH comprises 23 exons and spans over 94 kb of genomic
DNA [37,40]. The first exon encodes the 5′untranslated
region of the mRNA and the N-terminal 18 amino acids that
organize the signal peptide. Each SCR in factor H is encoded
by a single exon except for SCR2, that is encoded by exons 3
and 4. Exon 10 does not contribute to the factor H transcript.
It is used exclusively in the alternative transcript that codes
for the FHL-1 molecule. Exon 10 encodes the last four amino
acids (Ser-Phe-Leu-Thr) and the 3′untranslated region of
FHL-1 [28].
The single nucleotide polymorphism (SNP) database at the
National Center for Biotechnology Information (NCBI) lists
a total of 569 SNPs in the human CFH gene region (locus ID:
3075). Of these, roughly a dozen are located in the CFH
proximal promoter region or result in an amino acid substi-
tution in the CFH coding sequence. The potential functional
implications of some of these CFH polymorphisms will be
discussed later in the context of the CFH–disease associations.
Of interest, however, is the observation that there is very
strong linkage disequilibrium (LD) in the CFH genomic
region, which reduces the genetic variability within this
region to the combination of four SNP–haplotype blocks
spanning the CFH and CFHR1–5 genes [41].
Levels of factor H in human plasma vary widely (116–
562 mg/ml) in the population. This variation is not a conse-
quence of CFH null alleles, which are extremely rare, but the
result of the combined effect of genetic and environmental
factors. Using variance-component methods [42] it was
determined that factor H plasma levels show an age-
dependent increase and are decreased in smokers [24]. Most
important, these studies showed that 63% of the variation in
plasma levels of factor H is determined genetically [herita-
bility (h2)=0·63 ⫾0·07; P<0·0001]. A genome-wide screen
in order to identify genes regulating the factor H trait pro-
vided suggestive evidence of linkage to three genomic
regions (1q32, 2p21–24 and 15q22–24) [24] and more
recently we have obtained evidence that demonstrates the
existence of low expression CFH alleles [43]. It is therefore
likely that genetic variations in both cis- and trans-regulatory
elements contribute to the variation in the levels of expres-
sionoffactorH.
C3b C3b C3b
Hep Hep
Hep
Sialic acid
CRP
Cofactor activity
Decay accelerating activity
Surface binding
Cell surface regulation
1 2 3 4 5 6 7 8 9 1011121314151617181920
Fig. 1. FunctionaldomainsincomplementfactorH.FactorHhas
three C3b-binding sites, short consensus repeats (SCR)1–4, SCR12–14
and SCR19–20, respectively [9–13]. Similarly, a total of three separate
binding sites for heparin and sialic acid have been identified in SCR7,
SCR13 and SCR19–20, respectively [14–17]. The critical sites for
co-factor activity/decay accelerating activity and cell surface regulation
at the N- and C-termini, respectively, are indicated. In addition to
C3b and polyanion binding sites, there are other domains in factor H
that have been shown to interact with plasma proteins or with
micoorganisms and that are interesting because of their potential
relevance in pathology. In this regard, it has been shown that factor H
binds to C-reactive protein (CRP) which may help to counteract and
inhibit the CRP-dependent alternative pathway activation induced by
damaged tissue [18,19]. The heparin- and CRP-binding sites in SCR7
are overlapping sites in which one substrate inhibits the binding of
the others [20].
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Rearrangements in the CFH genomic region
In close proximity to the CFH gene there are the genes
CFHR3,CFHR1,CFHR4,CFHR2 and CFHR5 encoding the
five factor H-related proteins (Fig. 2). Sequence analyses of
the CFH–CFHR1–5 gene region demonstrated the existence
of a number of large genomic duplications including differ-
ent exons of the CFH and CFHR1–5 genes (Fig. 3a). These
duplications range in size from 1·2 to 38 kb and present a
pairwise nucleotide identity from 85% to 97% [37]. Low-
copy repeats, or segmental duplications, such as these in the
CFH–CFHR1–5 gene region, are highly dynamic regions in
the genome and a potential source of additional genetic
variation in the CFH and CFHR1–5 genes through
mechanisms of gene conversion and non-homologous
recombination.
Several examples of gene conversion events between exon
23 of CFH and the homologous exon 6 of CFHR1 have been
documented recently [37,45]. Similarly, there is also robust
evidence of major rearrangements in the CFH–CFHR1–5
gene region that result in the deletion of the CFHR1 and
CFHR3 genes [41,46] and, occasionally, also in the generation
of CFH::CFHR1 hybrid genes [44] (see Fig. 3 for details).
These CFH–CFHR1–5 rearrangements can be identified
easily by MLPA (multiplex ligation-dependent probe ampli-
fication) technologies [44] or by Western blot in the case of
homozygote carriers [46]. Chromosomes carrying both the
deletion of the CFHR1 and CFHR3 genes and a CFH::CFHR1
hybrid gene are rare and associated specifically with aHUS
[44]. In contrast,the deletion of the CFHR1 and CFHR3 genes
(without rearrangements in CFH)isacommongeneticpoly-
morphism included in a single extended CFH haplotype that
associates with both lower risk to age-related macular degen-
eration (AMD) [41,47] and increased risk to aHUS [46].
Deletion of the CFHR1 and CFHR3 genes is not a recurrent
phenomenon, but the result of a single rearrangement event
that became fixed in the human population a long time ago
[47]. Additional rearrangements are likely to occur in the
CFH–CFHR1–5 region. For instance,there is one involving an
unequal cross-over between homologous regions in the 3′end
of the CFHR3 and CFHR4 that specifically removes the
CFHR1 and CFHR4 genes [48].
Fig. 2. Chromosomal location and structure of the factor H gene. (a) The human regulator of complement activation (RCA) gene cluster in 1q32.
The human RCA gene cluster spans a total of 21·45 cM and includes more than 60 genes of which 15 are complement-related genes. All of the
complement-related genes are arranged in tandem within two groups. The two groupings are a telomeric 900 kb-long DNA segment which contains
the C4BPB,C4BPA,C4BPAL1,C4BPAL2,DAF,CR2,CR1,MCPL1,CR1L1 and MCP genes and a centromeric 650 kb-long DNA segment that contains
CFH,CFHR3,CFHR1,CFHR4,CFHR2 and CFHR5, as well as the gene coding for the B subunit of the coagulation factor XIII, F13B. These two gene
groups are separated by 14·59 cM, a large amount of DNA-containing genes that are unrelated to complement and that have very diverse functions
[38]. It is generally accepted that these complement regulatory genes share a common ancestor from which they originated by multiple events of gene
duplication. (b) Structure of CFH, showing a diagram of the 23 exons and the two alternative splicing products of the CFH gene.Exon10doesnot
contribute to the factor H transcript but it is utilized for the FHL-1 molecule. The figure also shows a Western blot, using a monoclonal antibody
(35H9) that recognizes both factor H and FHL-1, to illustrate the relative amounts of these proteins in normal human plasma.
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Genetics of human factor H
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Factor H disease associations
Several reports in recent years have stablished that mem-
branoproliferative glomerulonephritis type II (MPGN2)
[49–52], atypical haemolytic uraemic syndrome (aHUS)
[37,53–55] and AMD [27,56–58] are associated with muta-
tions or polymorphisms in the CFH gene. The data available
support the hypothesis that AP dysregulation is a unifying
pathogenetic feature of these diverse conditions. They also
illustrate a remarkable genotype–phenotype correlation in
which distinct genetic variations at CFH predispose specifi-
cally to aHUS, AMD or MPGN2. As described below, func-
tional characterization of these CFH genetic variations is
helping to understand the molecular basis underlying these
pathologies.
Membranoproliferative glomerulonephritis
Membranoproliferative glomerulonephritis (MPGN) is an
uncommon cause of chronic nephritis characterized by pro-
liferation of mesangial and endothelial cells and by thicken-
ing of the peripheral capillary walls (due to subendothelial
immune and/or intramembranous dense deposits) that on
light microscopy present a double-contour appearance.
MPGN may be secondary to autoimmune diseases, chronic
infections and malignancies or idiopathic, which accounts
for approximately 5% of primary renal causes of nephrotic
syndrome and affects predominantly children and young
adults (6–30 years). Three distinct types of primary
(idiopathic) MPGN have been described based on im-
munofluorescence staining, ultrastructural appearance and
Fig. 3. ThecomplementfactorHgene(CFH)–CFHR1–5 gene subregion of the regulator of complement activation (RCA) gene cluster. (a)
Genomic organization of the CFH and CFHR1–5 genes and location of low copy number repeats. Arrows represent the genes with their names
above. The boxes underneath indicate the sequence repeats. Low copy repeats are named with the same letter (i.e. A, A′,A′′). A grey colour-code is
used to identify the different repeats. The figure shows two chromosomes aligned by the B and B′repeats to illustrate the CFH–CFHR1 genomic
that occurred through non-homologous recombination between a 23 kb-long repeat region in the 3′end of the CFH and CFHR1 genes, labelled B
and B′, respectively. (b) Deletion of the CFHR1 and CFHR3 genes and generation of a CFH::CFHR1 hybrid gene.Therearrangementmarked2is
relatively common in multiple African and European populations. This rearrangement involves non-homologous recombination between the B
and B′homologous regions downstream of the CFH and CFHR1 genes and results in no sequence-modification of the CFH gene. A second
rearrangement (labelled 1) is much less frequent and found associated exclusively with atypical haemolytic uraemic syndrome (aHUS).
Non-homologous cross-over in this case occurred between the B and B′homologousregionsinintron21ofCFH and intron 4 of CFHR1 and
results in generation of a hybrid CFH::CFHR1 gene. The hybrid gene consists of the first 21 exons of CFH [encoding SCRs 1–18 of CFH] and the
last two exons of CFHR1 (encoding SCR4 and 5 of CFHR1) [44]. Amino acid sequences of CFH exon 23 and CFHR1 exon 6 are aligned to illustrate
two amino acid differences between them (S1191L/V1197A) that are present in the protein product of the hybrid gene. These amino acid changes in
SCR20 are associated with aHUS and are identical to those present in the CFH mutant protein, also associated with aHUS, that generates by gene
conversion [45].
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complement profiles. The light microscopy features and
clinical presentation are similar among the three types.
Hypocomplementaemia is a characteristic finding with all
types of MPGN, although the three types present different
mechanisms of complement activation. Types I (MPGN1)
and III (MPGN3) are variants of immune-complex-
mediated disease, whereas type II (MPGN2) has no known
association with immune complexes [59].
MPGN2 is very rare. Its morphological hallmark is the
presence of dense deposits within the glomerular basement
membrane (GBM), as resolved by electron microscopy. The
chemical composition of these dense deposits is unknown.
Notably, immunoglobulin (IgG) is absent from them and
other regions of the glomerulus, which excludes a role for
immune complexes in dense deposits formation. MPGN2 is
associated with complement abnormalities that lead to
intense deposition of C3c in GBM deposits and persistent
reduction of C3 serum levels. Among the different factors
associated with these complement abnormalities are factor
H deficiencies due to mutations in the CFH gene. Approxi-
mately half a dozen MPGN patients are described in the
literature in which the deficiency of factor H, both heterozy-
gous and homozygous, has been associated with the devel-
opment of the disease. In all but one of these MPGN cases
the factor H deficiency is caused by mutations in CFH that
result in truncations or amino acid substitutions that impair
secretion of factor H into the circulation [49,60,61] (Fig. 4).
The exception is DK224, a CFH mutation that results in the
deletion of a lysine residue at position 224 [51]. K244 is
located in SCR4 within the complement regulatory region of
factor H (Fig. 1). Consistent with the location of the muta-
tion, functional studies of factor H DK224 have shown that
binding to C3b is weak and that both factor I-mediated C3b
co-factor activity and AP C3-convertase decay-accelerating
activity of factor H DK224 are reduced markedly. In contrast,
and as expected from an intact C-terminal domain, the
mutant factor H DK224 protein shows normal binding to
heparin, C3d and human umbilical vein endothelial cells
[51]. The co-existence of a functionally inactive factor H
(homozygous DK224 mutation), or a factor H deficiency,
with a complement activator such as C3NeF, probably exac-
erbates a situation of chronic complement activation and
Fig. 4. ComplementfactorHgene(CFH) mutations in MPGN and atypical haemolytic uraemic syndrome (aHUS) patients. The figure shows a
diagram of the structure of human factor H with the 20 SCRs. The location of the missense mutations characterized thus far in
membranoproliferative glomerulonephritis (MPGN) and aHUS patients is indicated. The position of the Tyr402His polymorphisms associated
strongly with predisposition to AMD is highlighted in bold. Note that mutations associated with aHUS are clustered in the C-terminus, the region
of factor H that is critical for the control of C3b deposited on cell surfaces.
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Genetics of human factor H
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results in the complete consumption of C3 in plasma that
characterizes MPGN patients [51].
In addition to mutations in CFH, deficiencies of factor H
due to inhibitory autoantibodies have also been reported in
some MPGN patients, which also lead to accumulation of
the AP C3-convertase, chronic C3 consumption and hypo-
complementaemia [62].
Altogether,these genetic and functional data illustrate that
those alterations that decrease factor H in plasma, or elimi-
nate its complement regulatory activity, lead to unrestricted
activation of the AP of complement, causing damage to
glomerular cells and deposition of complement product in
the GBM. The severe dysregulation of the AP of complement
activation observed in MPGN2 is consistent with animal
data that present this renal phenotype. In the pig, factor H
deficiency results in a progressive glomerulonephritis,
similar to human MPGN2, which leads to renal failure [63].
Similarly, the factor H knock-out mice develop spontane-
ously a glomerulonephritis that also resembles human
MPGN2 [64]. These factor H-deficient animals have been
very useful to demonstrate that the uncontrolled activation
of C3 in plasma that results from the lack of factor H is
essential for the development of MPGN2 [64]. Further
studies are, however, necessary to unravel the precise
molecular events that end up in MPGN2.
Although the majority of patients with MPGN2 do not
have disease-causing mutations in CFH, some common
alleles of CFH (and also of CFHR5) have been found to be
increased significantly among these patients, supporting
further the critical role of genetic variations in the CFH
genomic region in the pathogenesis of MPGN2. One of these
polymorphisms conferring predisposition to MPGN2 is the
His402 allele of CFH [65,66], a major predisposing factor to
AMD (see below).
Haemolytic uraemic syndrome (HUS)
HUS is characterized by thrombocytopenia, Coomb’s test
negative microangiopathic haemolytic anaemia and acute
renal failure. The typical form of HUS follows a diarrhoeal
prodrome and is associated with 0157:H7 Esherichia coli
infections. However, 5–10% of HUS patients lack an asso-
ciation with infection. This atypical form of HUS (aHUS)
occurs in both adults and in very young children and has the
poorest long-term prognosis. Recurrences in aHUS are
common with a mortality rate that approaches 30%. aHUS
has an incidence of about 2/106per year and a prevalence of
1/105children in the whole of the European Union.
Endothelial cell injury appears to be the primary event in
the pathogenesis of HUS. The microvascular lesion of HUS
consists of vessel wall thickening with endothelial swelling
and detachment from the basement membrane. The endot-
helial damage triggers a cascade of events that result in the
formation of platelet-fibrin hyaline microthrombi that
occlude arterioles and capillaries. A hallmark of HUS is the
presence of schistocytes (fragmented cells) that generate as
the red blood cells traverse these partially occluded
microvessels [67].
aHUS is associated with mutations or polymorphisms in
the genes encoding the complement regulatory proteins
factorH(CFH) [37,44,53–55,68,69], membrane co-factor
protein (MCP) [70–73] and factor I (CFI) [74,75] and with
mutations in the complement activating components factor
B(CFB) [76] and C3 genes [77]. Importantly, mutations in
the complement regulators factor H, MCP and factor I are
loss-of-function mutations [73,74,78] while mutations in
the complement activator factor B are gain-of-function
mutations [76]. These data establish unequivocally the criti-
cal role of complement AP dysregulation in the pathogenesis
of aHUS and illustrate that complement dysregulation may
result from either a defect in the regulatory proteins or an
abnormally increased activity of the alternative complement
pathway activators.
Missense mutations in the C-terminal region of factor H
are the most prevalent genetic alterations among aHUS
patients (Fig. 4). In a significant number of patients muta-
tions in the C-terminal region of factor H are the result of
gene conversion events between exon 23 of CFH and the
homologous exon 6 of CFHR1 [45] or of genomic rearrange-
ments creating CFH::CFHR1 hybrid genes [44]. An updated
record of all mutations associated with aHUS can be found
at the FH–HUS database (http://www.fh-hus.org/).
In contrast with CFH mutations associated with MPGN2,
CFH mutations associated with aHUS rarely result in hypo-
complementaemia or decreased factor H plasma levels. Most
aHUS-associated factor H mutant proteins express normally
and present normal co-factor activity for the factor
I-mediated proteolytic inactivation of C3b in plasma [37,78].
As indicated, aHUS-associated CFH mutations cluster in the
C-terminus of the protein, a region that is critical to control
activation of complement on cell surfaces. Consistent with
this location, carriers of these CFH mutations express factor
H molecules that present normal regulatory activity in
plasma but a limited capacity to protect cells from comple-
ment lysis [69,78,79]. These findings fit well with the identi-
fication of aHUS-associated loss-of-function mutations in
MCP and CFI for the reason that the MCP and factor I
mutations also lead to decreased protection of host cells from
complement lysis without affecting significantly complement
homeostasis in plasma [80]. The combination of both an
active complement system in plasma and a defective protec-
tion of cellular surfaces portrays aHUS as a situation of
‘autolesion’ caused by the uncontrolled activation of comple-
ment on cell surfaces. By decreasing concentrations of factor
H or factor I in plasma, or MCP on cell surfaces, aHUS-
associated mutations predispose to disease. In a situation that
triggers complement activation, deposition and amplifica-
tion of C3b on the microvasculature cellular surfaces cannot
be controlled and results in tissue damage and destruction.
This is clearly distinct from the lack of complement regula-
TRANSLATIONAL MINI-REVIEW SERIES ON COMPLEMENT FACTOR H
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Journal compilation © 2008 British Society for Immunology, Clinical and Experimental Immunology,151: 1–13

tion in plasma, leading to complete C3 consumption and
severe hypocomplementaemia, that characterizes MPGN2
patients with factor H deficiency due to mutations in CFH.
While mutations at the C-terminus of factor H are dis-
tinctive of aHUS, there are some aHUS patients with partial
factor H deficiency due to mutations in the CFH gene
[81–84]. These individuals develop aHUS and not MPGN2
mainly because partial factor H deficiencies, like mutations
in SCR19-20, affect primarily the control of complement
activation on cellular surfaces [85]. In addition, genetic and
environmental factors may provide a‘context’ that influences
the pathological outcome for some of these factor H
deficiencies. Thus, concurrence of factor H deficiencies with
other mutations that decrease protection to host cells have
been described in aHUS [37,78], whereas the coincidence of
factor H deficiencies with strong complement activators
such as C3NeF may be critical in MPGN2 [51].
Mutations in CFH,MCP,CFI,CFB and C3 reveal the
molecular defect in approximately 50% of the aHUS
patients. To identify additional aHUS susceptibility factors,
the complement regulator genes have been analysed further
in genetic association studies [53,70]. These and subsequent
replication studies [66,71,86] unravelled two relatively
frequent CFH and MCP alleles (CFH–H3 and MCPggaac
haplotypes) that were significantly more frequent in aHUS
patients (either with or without CFH,MCP,CFI or CFB
mutations) than in controls. Moreover, in a significant
number of aHUS families where CFH,MCP,CFI or CFB
mutations segregated with the phenotype aHUS, it could be
shown that the proband had inherited the allele carrying the
mutation from one parent and an allele carrying the disease-
associated CFH and/or MCP haplotype from the other
parent. Most interestingly, the healthy CFH,MCP,CFI or
CFB mutation carriers in these families did not inherit the
aHUS-associated CFH and MCP polymorphisms [53,76,87].
Both CFH–H3 and MCPggaac haplotypes include SNPs
located in the promoter region of CFH and MCP that have
potential functional implications in the expression of factor
H and MCP [53,70]. Although additional studies are needed
to fully characterize functionally these CFH and MCP hap-
lotypes, the association of CFH–H3 and MCPggaac with
aHUS is extremely important because it indicates that
common variations at the CFH and MCP genes predispose
to aHUS in the absence of mutations in CFH,MCP,CFI or
CFB and that even in carriers of mutations in these genes,
these CFH and MCP variations may be needed for full mani-
festation of the disease. In fact, it is now well established that
concurrence of different susceptibility alleles greatly influ-
ences predisposition to aHUS and provides an explanation
for the incomplete penetrance of aHUS (close to 50%) in
carriers of mutations in CFH,MCP,CFI and CFB [70,76,87].
In the Spanish aHUS cohort (n=98 unrelated patients),
seven patients (7%) carry more than one mutation in the
complement genes (CFH,MCP,CFI and CFB). In addition,
in the 28 patients with mutations in CFH,MCP,CFI and
CFB, the allele frequencies of CFH–H3 and MCPggaac hap-
lotypes is increased from 0·19 to 0·34 [controls versus aHUS;
P=0·012; odds ratio (OR), 95% confidence interval
(CI) =2·27 (1·21–4·27)] and from 0·29 to 0·45 [controls
versus aHUS; P=0·027; OR, 95% CI) =2·77 (1·54–4·95)],
respectively (Goicoechea de Jorge et al., unpublished).
Recently, two additional polymorphisms in the CFH
genomic region have been reported to influence predisposi-
tion to aHUS. The CFH–H1 haplotype was found to be
associated with lower risk of aHUS [66]. Similarly, homozy-
gosity for the deletion of the CFHR1 and CFHR3 genes asso-
ciated strongly with increased risk of aHUS [46]. Moreover,
it has been shown that approximately 10% of aHUS patients,
mostly children, present auto-antibodies to factor H and that
these antibodies have functional consequences similar to
those caused by the mutations in the C-terminal region of
factor H [88,89]. Interestingly, individuals presenting anti-
factor H antibodies are, with very few exceptions, homozy-
gous for the deletion of the CFHR1 and CFHR3 genes, which
make unclear whether the deletion of these genes and the
presence of auto-antibodies are independent risk factors for
aHUS [48,90,91].
In conclusion, genetic and functional analyses have estab-
lished that aHUS involves alternative complement dysregula-
tion and probably develops as a consequence of defective
protection of cellular surfaces from complement activation
due to an improper function of complement regulatory
proteins. Multiple hits, involving plasma and membrane-
associated complement regulatory proteins, as well as
complement activators, are probably required to cause dys-
regulation and impair protection to host tissues significantly.
Environmental factors that activate complement probably
modulate genetic predisposition and are also very important
in aHUS. Infection, immunosuppressive drugs, cancer thera-
pies, oral contraceptives, pregnancy or childbirth are impor-
tant factors that trigger aHUS in a significant number of
patients. In carriers of multiple strong aHUS risk factors the
contribution of the environment is probably minor. On the
other hand, strong environmental factors may compensate
for low genetic predisposition, which perhaps helps to explain
the severe or fatal outcome of a small percentage of individu-
als with the more common diarrhoea-associated typical HUS.
AMD
AMD is one of the most common causes of visual disability
in the elderly in developed countries. The hallmark of early-
stage disease is the development of drusen, lipoproteina-
ceous deposits localized between the retinal pigment
epithelium (RPE) and Bruch’s membrane. Later, an exten-
sive atrophy of the RPE and overlaying photoreceptor cells
(geographical atrophy; GA) or aberrant choroidal angiogen-
esis is observed. This choroidal neovascularization (CNV)
under the macular area is the leading cause for blindness.
Although the pathogenesis of AMD is still unclear, it has
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been proposed that inflammatory response play an impor-
tant role in the development of AMD [92].
AMD is a multi-factorial disease, influenced by age, eth-
nicity and a combination of environmental and genetic risk
factors. Genetic predisposition in AMD has been suggested
based on familial segregation and twin studies, involving
several candidate genes such as ABCA4, APOE, FBLN5,
ELOVL4 and TLR4. However, the individual contribution of
these genes to overall AMD prevalence appears relatively
minor [93]. Two major AMD susceptibility loci (1q31, CFH,
and 10q26, LOC387715/HTRA1) that contribute indepen-
dently to AMD disease risk have been identified recently by
candidate region linkage studies and whole genome associa-
tion analyses [27,56–58,94].
The most studied SNP at the CFH locus is rs1061170,
which causes a Tyr402His amino acid substitution in
complement factor H. Several independent studies have
shown that the allele 402His confers a significantly increased
risk to AMD in many different populations with an OR
between 2·1 and 7·4 [27,56–58]. Interestingly, the frequency
of the 402His allele varies greatly between populations,
which may contribute to the observed differences in the
incidence of AMD among different ethnic groups [47].
The Tyr402His polymorphism lies in the SCR7 of factor
H, within the cluster of positively charged amino acids
implicated in the binding of heparin, C-reactive protein
(CRP) and M protein [20] (Fig. 1). Structural studies have
shown that the substitution occurs towards the centre of
SCR7 and that the 3D structures of both allotypes are oth-
erwise identical [95]. In vitro functional studies with factor H
recombinant fragments indicate that the substitution of Tyr
for His at position 402 alters the binding specificity of SCR7
for different glycosaminoglycans [96,97] and decreases its
binding to retinal pigment epithelial cells [98], although the
physiological relevance of these observations is still unclear.
It has also been reported that the Tyr402His polymorphism
influences the binding of factor H to C-reactive protein
[98–100], but the difficulties in replicating these data ques-
tion the implication of the Tyr402His polymorphism in
C-reactive protein binding [101,102].
Within the CFH gene, downstream of the SNP-haplotype
block including the Tyr402His polymorphism, there is a
second SNP LD group containing three polymorphisms, a
synonymous SNP in exon 11 (rs2274700) and two intronic
SNPs (rs1410996 and rs7535263), showing a stronger asso-
ciation with disease susceptibility than the Tyr402His variant
[103,104]. Although these polymorphisms and the His402
variant form part of an extended CFH haplotype, they were
described as independent predisposition variants that may
be important in regulating the expression of CFH, or other
nearby complement genes or both [103].
In addition to these CFH variants conferring increased risk
to AMD, two common extended haplotypes in CFH gene
[27,41,104] and two common SNPs in complement factor B
[105] have been described associated with lower risk to AMD.
CFH haplotype H2, decreased markedly in AMD [27], is
also decreased in MPGN2 and aHUS [66] (Fig. 5). CFH
haplotype H2 carries the Ile62 factor H variant within the
C3b binding site in the N-terminal region (SCR1–4) that is
essential for the factor I-mediated co-factor and decay-
accelerating activities of factor H (Fig. 1). Substitution of Val
for Ile at position 62 may increase the factor H regulatory
activity [106] and thus confer lower risk to AMD, MPGN2
and aHUS by reducing AP activation.
CFH haplotype H4 is also associated with decreased risk
of AMD [41,66], but not to MPGN2 or aHUS [66] (Fig. 5).
Interestingly, this CFH haplotype is also unique because it
carries a deletion of the CFHR1 and CFHR3 genes [41].
Although it has been indicated that CFHR1 and CFHR3
proteins have the potential to compete with factor H for C3b
binding [41], the potential benefit of the absence of CFHR1
and CFHR3 proteins is puzzling, in particular because it has
been reported recently that the deletion of CFHR1 and
CFHR3 genes is associated with increased risk to aHUS [46].
Two factor B polymorphisms were identified that were
protective for AMD [105], one of which (32Q) had been
reported previously to reduce the haemolytic activity of
factor B [107] and the other, in the signal peptide, was
suggested to modulate secretion of factor B. The observed
protection in each case was ascribed to a reduced activity
of the complement alternative pathway.
The identification of CFH as a major susceptibility locus
for AMD and the characterization of multiple genetic
variants in the CFH–CFHR1–5 and CFB genomic regions
conferring risk or protection to AMD indicate that the
complement system plays a significant role in AMD
pathogenesis. Further studies are, however, needed to deter-
mine the functional consequences of the CFH variants asso-
ciated with AMD and to identify the molecular events
influenced by the complement system in the pathogenesis of
AMD. In the meantime, definition of the AMD at-risk or
protective factors associated with the CFH,LOC387715/
HTRA1 and CFB genes has allowed the development of risk
models for AMD [87,94,104] that should be very helpful to
delineate the individual risk to develop AMD,facilitating the
implementation of preventive therapeutics.
CFH genotype–phenotype correlations
AMD [27,56–58], aHUS [37,53–55] and MPGN2
[49,50,52,103] are distinct pathological entities that are all
associated with mutations and polymorphisms in the gene
(CFH), which support the hypothesis that AP dysregulation
is a unifying pathogenic feature of these diverse conditions.
However, there are differences in the CFH genetic variants
conferring risk or protection to one or other disease, indi-
cating the existence of a peculiar genotype–phenotype
relationship. AMD and MPGN2 share pathological similari-
ties with accumulation of complement-containing debris
within the eye and kidney, respectively. Indeed, AMD-like
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8© 2008 The Author(s)
Journal compilation © 2008 British Society for Immunology, Clinical and Experimental Immunology,151: 1–13

pathology is well-recognized in patients with MPGN2 [108].
The hallmark of AMD is drusen, complement-containing
material that accumulates beneath the retinal pigmented
epithelium [92], while in MPGN2 accumulation of C3 and
electron-dense material is seen along the GBM [59]. In
contrast to these ‘debris-associated’ conditions, aHUS is
characterized by renal endothelial injury and thrombosis
(thrombotic microangiopathy) resulting in haemolytic
anaemia, thrombocytopenia and renal failure.
Consistent with these pathological differences, we have
discussed earlier in this review that the complete factor H
deficiency in humans, pigs and mice is associated with
MPGN2, while aHUS-associated CFH mutations cluster
within the carboxy-terminal SCR of the protein. In addition,
CFH association data derived from a comparative genetic
analysis, using a minimal set of informative CFH SNPs, in
subjects with aHUS, AMD and MPGN2 from a single popu-
lation showed no overlapping between CFH at-risk poly-
morphisms for aHUS and AMD (or MPGN2) [66] (Fig. 5).
Recently, this CFH genotype–phenotype correlation has
been established formally in a murine model. Factor
H-deficient mice (Cfh–/–) develops MPGN2 as a consequence
of the massive activation of C3 [64]. These mice present
very low levels of C3 and complement activities in plasma.
Introduction into Cfh–/– mice of a transgenic factor H mol-
ecule (FHD16-20) that mimics the human aHUS-associated
mutations restored the C3 levels and the complement activ-
ity in the plasma of these factor H-deficient animals. As a
result, Cfh–/–FHD16-20 animals switch their disease phenotype
from MPGN2 to aHUS [66]. These data validate the previ-
ous hypothesis [37,78], establishing definitively that the
combination of active complement in plasma with a
decreased protection of cell surfaces leads to aHUS.
The challenge now is to understand the functional conse-
quences of all the genetic variations in the complement genes
associated with high and low risk to aHUS, MPGN2 and
AMD and to determine how they influence the complex
interplay of regulators and activators in the homeostasis of
the complement system, in the elimination of cellular debris
and in the protection of the host cells.
Concluding remarks
We have reviewed recent advances in the genetics of factor H
and summarized overwhelming evidence that associates dif-
ferent genetic variants of factor H with ocular and renal
disease. The data available support a strong genotype–
phenotype correlation between CFH and these conditions
Fig. 5. ComplementfactorHgene(CFH) haplotypes and their association with disease. Schematic illustration of the CFH exon structure showing
the location of the six single nucleotide polymorphisms (SNPs) included in these studies. These SNPs represent a minimal informative set for
genetic variation within the CFH gene. Haplotype frequencies in the control and patient cohorts were estimated using the expectation maximization
(EM) algorithm implemented by the SNPStats software (available on-line at: http://bioinfo.iconcologia.net/SNPstats). CFH haplotypes with a
frequency >1% are shown. The frequency of each CFH haplotype was compared between the controls and the atypical haemolytic uraemic
syndrome, age-related macular degeneration and membranoproliferative glomerulonephritis type II cohorts and the P-values and the odds ratios
(OR) were calculated. Risk haplotypes are shaded black, while protective haplotypes are shaded in grey. P-values were derived using the two-sided
Fisher’s exact test. OR and 95% confidence intervals are shown. The nucleotide and amino acid numbering are referred to the translation start site
(A in ATG is +1; Met is +1) as recommended by the Human Genome Variation Society. This figure is an updated version of that published in
Pickering et al. [66].
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suggesting that, despite a common link involving comple-
ment dysregulation, there are distinct functional alterations
in factor H that are essential in the pathogenesis of these
disorders. It is now well established that mutations or poly-
morphisms altering the C3b/polyanions binding site located
at the C-terminal region of factor H are associated strongly
with aHUS. Specifically, these mutations impair the capacity
of factor H to protect host cells. Accordingly, aHUS is emerg-
ing as a paradigm of disease resulting from the inefficient
protection of the host cellular surfaces from complement
activation. On the other hand, mutations that disrupt the
plasma activities of factor H so that it fails to control comple-
ment activation result in a massive activation of C3 that
causes MPGN2. AMD associates strongly and specifically
with a common extended CFH haplotype carrying the
402His polymorphism, but the molecular bases of this asso-
ciation are controversial and still unclear. There are also
common CFH haplotypes that associate specifically with
lower risk to AMD. Understanding the functional conse-
quences of the different CFH genetic variants should help to
determine the molecular events that are critical in the patho-
genesis of AMD. These studies, and the generation of animal
models for the different disease-associated CFH genetic vari-
ants, should guide the future development of effective aHUS,
MPGN and AMD therapeutics.
Acknowledgements
S. R. de C. is supported by funds provided by the Spanish
Ministerio de Educación y Cultura (SAF2005-00913).
References
1 Law SKA, Reid KBM. Complement, 2nd edn. Oxford: IRL Press,
1995.
2 Pangburn MK, Schreiber RD, Müller-Eberhard HJ. Human
complement C3b inactivator: isolation, characterization,and dem-
onstration of an absolute requirement for the serum protein
beta1H for cleavage of C3b and C4b in solution. J Exp Med 1977;
146:257–70.
3 Weiler JM, Daha MR, Austen KF, Fearon DT. Control of the ampli-
fication convertase of complement by the plasma protein beta1H.
Proc Natl Acad Sci USA 1976; 73:3268–72.
4 Whaley K, Ruddy S. Modulation of the alternative complement
pathwaysbybeta1Hglobulin.JExpMed1976; 144:1147–63.
5 Fearon DT. Regulation by membrane sialic acid of beta1H-
dependent decay-dissociation of amplification C3 convertase of the
alternative complement pathway. Proc Natl Acad Sci USA 1978;
75:1971–5.
6 Kazatchkine MD, Fearon DT, Austen KF. Human alternative
complement pathway: membrane-associated sialic acid regulates
the competition between B and beta1 H for cell-bound C3b.
J Immunol 1979; 122:75–81.
7 Pangburn MK, Schreiber RD,Muller-Eberhard HJ. C3b deposition
during activation of the alternative complement pathway and the
effect of deposition on the activating surface. J Immunol 1983;
131:1930–5.
8 Ripoche J, Day AJ, Harris TJ, Sim RB. The complete amino acid
sequence of human complement factor H. Biochem J 1988;
249:593–602.
9 Kuhn S, Skerka C, Zipfel PF. Mapping of the complement regula-
tory domains in the human factor H-like protein 1 and in factor
H1. J Immunol 1995; 155:5663–70.
10 Alsenz J, Schulz TF, Lambris JD, Sim RB, Dierich MP. Structural
and functional analysis of the complement component factor H
with the use of different enzymes and monoclonal antibodies to
factor H. Biochem J 1985; 232:841–50.
11 Gordon DL, Kaufman RM, Blackmore TK, Kwong J, Lublin DM.
Identification of complement regulatory domains in human factor
H. J Immunol 1995; 155:348–56.
12 Jokiranta TS, Zipfel PF, Hakulinen J et al. Analysis of the recogni-
tion mechanism of the alternative pathway of complement by
monoclonal anti-factor H antibodies: evidence for multiple inter-
actions between H and surface bound C3b. FEBS Lett 1996;
393:297–302.
13 Prodinger WM, Hellwage J, Spruth M, Dierich MP, Zipfel PF. The
C-terminus of factor H: monoclonal antibodies inhibit heparin
binding and identify epitopes common to factor H and factor
H-related proteins. Biochem J 1998; 331:41–7.
14 Blackmore TK, Hellwage J, Sadlon TA et al. Identification of the
second heparin-binding domain in human complement factor H.
J Immunol 1998; 160:3342–8.
15 Blackmore TK, Sadlon TA, Ward HM, Lublin DM, Gordon DL.
Identification of a heparin binding domain in the seventh short
consensus repeat of complement factor H. J Immunol 1996;
157:5422–7.
16 Pangburn MK, Atkinson MA, Meri S. Localization of the heparin-
binding site on complement factor H. J Biol Chem 1991;
266:16847–53.
17 Ram S, Sharma AK, Simpson SD et al. A novel sialic acid binding
site on factor H mediates serum resistance of sialylated neisseria
gonorrhoeae. J Exp Med 1998; 187:743–52.
18 Kaplan MH, Volanakis JE. Interaction of C-reactive protein com-
plexes with the complement system. I. Consumption of human
complement associated with the reaction of C-reactive protein with
pneumococcal C-polysaccharide and with the choline phosphati-
des, lecithin and sphingomyelin. J Immunol 1974; 112:2135–47.
19 Mold C, Kingzette M, Gewurz H. C-reactive protein inhibits pneu-
mococcal activation of the alternative pathway by increasing the
interaction between factor H and C3b. J Immunol 1984; 133:882–5.
20 Giannakis E, Jokiranta TS, Male DA et al. A common site within
factor H SCR 7 responsible for binding heparin, C-reactive protein
and streptococcal M protein. Eur J Immunol 2003; 33:962–9.
21 Rodriguez de Cordoba S, Esparza-Gordillo J, Goicoechea de Jorge
E, Lopez-Trascasa M, Sanchez-Corral P. The human complement
factor H: functional roles, genetic variations and disease
associations. Mol Immunol 2004; 41:355–67.
22 Morris KM, Aden DP, Knowles BB, Colten HR. Complement bio-
synthesis by the human hepatoma-derived cell line HepG2. J Clin
Invest 1982; 70:906–13.
23 Schwaeble W, Zwirner J, Schulz TF, Linke RP, Dierich MP, Weiss
EH. Human complement factor H: expression of an additional
truncated gene product of 43 kDa in human liver. Eur J Immunol
1987; 17:1485–9.
24 Esparza-Gordillo J, Soria JM, Buil A et al. Genetic and environ-
mental factors influencing the human factor H plasma levels.
Immunogenetics 2004; 56:77–82.
TRANSLATIONAL MINI-REVIEW SERIES ON COMPLEMENT FACTOR H
S. Rodríguez de Córdoba and E. Goicoechea de Jorge
10 © 2008 The Author(s)
Journal compilation © 2008 British Society for Immunology, Clinical and Experimental Immunology,151: 1–13

25 Chen M, Forrester JV, Xu H. Synthesis of complement factor H by
retinal pigment epithelial cells is down-regulated by oxidized pho-
toreceptor outer segments. Exp Eye Res 2007; 84:635–45.
26 Friese MA, Hellwage J, Jokiranta TS et al. FHL-1/reconectin and
factor H: two human complement regulators which are encoded by
the same gene are differently expressed and regulated. Mol
Immunol 1999; 36:809–18.
27 Hageman GS, Anderson DH, Johnson LV et al. A common haplo-
type in the complement regulatory gene factor H (HF1/CFH) pre-
disposes individuals to age-related macular degeneration. Proc Natl
Acad Sci USA 2005; 102:7227–32.
28 Estaller C, Schwaeble W, Dierich M, Weiss EH. Human comple-
ment factor H: two factor H proteins are derived from alternatively
spliced transcripts. Eur J Immunol 1991; 21:799–802.
29 Misasi R, Huemer HP, Schwaeble W, Sölder E, Larcher C, Dierich
MP. Human complement factor H: an additional gene product of
43 kDa isolated from human plasma shows cofactor activity for the
cleavage of the third component of complement. Eur J Immunol
1989; 19:1765–8.
30 Zipfel PF, Skerka C. FHL-1/reconectin: a human complement and
immune regulator with cell-adhesive function. Immunol Today
1999; 20:135–40.
31McRaeJL,CowanPJ,PowerDAet al. Human factor H-related
protein 5 (FHR-5). A new complement-associated protein. J Biol
Chem 2001; 276:6747–54.
32 Skerka C, Hellwage J, Weber W et al. The human factor H-related
protein 4 (FHR-4). A novel short consensus repeat-containing
protein is associated with human triglyceride-rich lipoproteins.
J Biol Chem 1997; 272:5627–34.
33 Zipfel PF, Jokiranta TS, Hellwage J, Koistinen V, Meri S. The factor
H protein family. Immunopharmacology 1999; 42:53–60.
34 Zipfel PF, Skerka C. Complement factor H and related proteins: an
expanding family of complement-regulatory proteins? Immunol
Today 1994; 15:121–6.
35 Díaz-Guillén MA, Rodríguez de Córdoba S, Heine-Suñer D. A
radiation hybrid map of complement factor H and factor H-related
genes. Immunogenetics 1999; 49:549–52.
36 McRae JL, Murphy BE, Eyre HJ, Sutherland GR, Crawford J, Cowan
PJ. Location and structure of the human FHR-5 gene. Genetica
2002; 114:157–61.
37 Perez-Caballero D, Gonzalez-Rubio C, Gallardo ME et al. Cluster-
ing of missense mutations in the C-terminal region of factor H in
atypical hemolytic uremic syndrome. Am J Hum Genet 2001;
68:478–84.
38 Rodriguez de Cordoba S, Diaz-Guillen MA, Heine-Suñer D.
An integrated map of the human regulator of complement
activation (RCA) gene cluster on 1q32. Mol Immunol 1999;
36:803–8.
39 Rodriguez de Cordoba S, Lublin DM, Rubinstein P, Atkinson JP.
Human genes for three complement components that regulate
the activation of C3 are tightly linked. J Exp Med 1985; 161:1189–
95.
40 Male DA, Ormsby RJ, Ranganathan S, Giannakis E, Gordon DL.
Complement factor H: sequence analysis of 221 kb of human
genomic DNA containing the entire fH, fHR-1 and fHR-3 genes.
Mol Immunol 2000; 37:41–52.
41 Hughes AE, Orr N, Esfandiary H, Diaz-Torres M, Goodship T,
Chakravarthy U. A common CFH haplotype, with deletion of
CFHR1 and CFHR3, is associated with lower risk of age-related
macular degeneration. Nat Genet 2006; 38:1173–7.
42 Almasy L, Blangero J. Multipoint quantitative-trait linkage analysis
in general pedigrees. Am J Hum Genet 1998; 62:1198–211.
43 TortajadaA,HakobyanS,GoicoecheadeJorgeEet al. Factor H
allele-specific quantification in Tyr402His heterozygotes reveals the
existence of low-expression alleles associated with atypical
haemolytic uraemic syndrome. Mol Immunol 2007; 44:3925.
44 Venables JP, Strain L, Routledge D et al. Atypical haemolytic
uraemic syndrome associated with a hybrid complement gene.
PLoS Med 2006; 3:e431.
45 Heinen S, Sanchez-Corral P, Jackson MS et al. De novo gene con-
version in the RCA gene cluster (1q32) causes mutations in
complement factor H associated with atypical hemolytic uremic
syndrome. Hum Mutat 2006; 27:292–3.
46 Zipfel PF, Edey M, Heinen S et al. Deletion of complement factor
H-related genes CFHR1 and CFHR3 is associated with atypical
hemolytic uremic syndrome. PLoS Genet 2007; 3:e41.
47 Hageman GS, Hancox LS, Taiber AJ et al. Extended haplotypes in
the complement factor H (CFH) and CFH-related (CFHR) family
of genes protect against age-related macular degeneration: charac-
terization, ethnic distribution and evolutionary implications. Ann
Med 2006; 38:592–604.
48 Martínez-Barricarte B, Goicoechea de Jorge E, Recalde S et al.
Complement factor H haplotypes and copy number variations of
the factor H-related genes in renal and ocular disorders. Mol
Immunol 2007; 44:3919–20.
49 Dragon-Durey M-A, Fremeaux-Bacchi V, Loirat C et al. Heterozy-
gous and homozygous factor H deficiencies associated with
hemolytic uremic syndrome or membranoproliferative glomerulo-
nephritis: report and genetic analysis of 16 cases. J Am Soc Nephrol
2004; 15:787–95.
50 Levy M, Halbwachs-Mecarelli MC, Guber G et al. H deficiency in
two brothers with atypical dense intramembraneous deposit
disease. Kidney Int 1986; 30:949–56.
51 Licht C, Heinen S, Jozsi M et al. Deletion of Lys224 in regulatory
domain 4 of factor H reveals a novel pathomechanism for dense
deposit disease (MPGN II). Kidney Int 2006; 70:42–50.
52 López-Larrea C, Dieguez MA, Enguix A, Dominguez O, Marin B,
Gomez E. A familial deficiency of complement factor H. Biochem
Soc Trans 1987; 15:648–9.
53 Caprioli J, Castelletti F, Bucchioni S et al. Complement factor H
mutations and gene polymorphisms in haemolytic uraemic syn-
drome: the C-257T, the A2089G and the G2881T polymorphisms
are strongly associated with the disease. Hum Mol Genet 2003;
12:3385–95.
54 Richards A, Buddles MR, Donne RL et al. Factor H mutations in
hemolytic uremic syndrome cluster in exons 18–20, a domain
important for host cell recognition. Am J Hum Genet 2001;
68:485–90.
55 Warwicker P, Goodship THJ, Donne RL et al. Genetic studies into
inherited and sporadic hemolytic uremic syndrome. Kidney Int
1998; 53:836–44.
56 Edwards AO, Ritter R, Abel KJ, Manning A, Panhuysen C, Farrer
LA. Complement factor H polymorphism and age-related macular
degeneration. Science 2005; 308:421–4.
57 Haines JL, Hauser MA, Schmidt S et al. Complement factor H
variant increases the risk of age-related macular degeneration.
Science 2005; 308:419–21.
58 Klein RJ, Zeiss C, Chew EY et al. Complement factor H poly-
morphism in age-related macular degeneration. Science 2005;
308:385–9.
TRANSLATIONAL MINI-REVIEW SERIES ON COMPLEMENT FACTOR H
Genetics of human factor H
11
© 2008 The Author(s)
Journal compilation © 2008 British Society for Immunology, Clinical and Experimental Immunology,151: 1–13

59 Appel GB, Terence CH, Hageman G et al. Membranoproliferative
glomerulonephritis type II (dense deposit disease): an update. J Am
Soc Nephrol 2005; 16:1392–403.
60 Ault BH, Schmidt BZ, Fowler NL et al. Human factor H deficiency.
Mutations in framework cysteine residues and block in H protein
secretion and intracellular catabolism. J Biol Chem 1997;
272:25168–75.
61 Zipfel PF, Heinen S, Jozsi M, Skerka C. Complement and diseases:
defective alternative pathway control results in kidney and eye
diseases. Mol Immunol 2006; 43:97–106.
62 Jokiranta TS, Solomon A, Pangburn MK, Zipfel PF, Meri S. Nephri-
togenic {lambda} light chain dimer: a unique human miniautoan-
tibody against complement factor H. J Immunol 1999; 163:4590–6.
63 Høgåsen K, Jansen JH, Mollnes TE, Hovdenes J, Harboe M. Heredi-
tary porcine membranoproliferative glomerulonephritis type II is
caused by factor H deficiency. J Clin Invest 1995; 95:1054–61.
64 Pickering MC, Cook HT, Warren J et al. Uncontrolled C3 activa-
tion causes membranoproliferative glomerulonephritis in mice
deficient in complement factor H. Nat Genet 2002; 31:424–8.
65 Abrera-Abeleda MA, Nishimura C, Smith JLH et al. Variations in
the complement regulatory genes factor H (CFH) and factor H
related 5 (CFHR5) are associated with membranoproliferative
glomerulonephritis type II (dense deposit disease). J Med Genet
2006; 43:582–9.
66 Pickering MC, Goicoechea de Jorge E, Martinez-Barricarte R et al.
Spontaneous hemolytic uremic syndrome triggered by comple-
ment factor H lacking surface recognition domains. J Exp Med
2007; 204:1249–56.
67 Noris M, Remuzzi G. Hemolytic uremic syndrome. J Am Soc
Nephrol 2005; 16:1035–50.
68 Caprioli J, Bettinaglio P, Zipfel PF et al. The molecular basis of
familial hemolytic uremic syndrome: mutation analysis of factor H
gene reveals a hot spot in short consensus repeat 20. J Am Soc
Nephrol 2001; 12:297–307.
69 Manuelian T, Hellwage J,Meri S et al. 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.
70 Esparza-Gordillo J, Goicoechea de Jorge E, Buil A et al. Predispo-
sition to atypical hemolytic uremic syndrome involves the con-
currence of different susceptibility alleles in the regulators of
complement activation gene cluster in 1q32. Hum Mol Genet 2005;
14:703–12.
71 Fremeaux-Bacchi V, Kemp EJ, Goodship JA, et al. The develop-
ment of atypical haemolytic–uraemic syndrome is influenced by
susceptibility factors in factor H and membrane cofactor protein:
evidence from two independent cohorts. J Med Genet 2005;
42:852–6.
72 Noris M, Brioschi S, Caprioli J et al. Familial haemolytic uraemic
syndrome and an MCP mutation. Lancet 2003; 362:1542–7.
73 Richards A, Kemp EJ, Liszewski MK et al. Mutations in human
complement regulator, membrane cofactor protein (CD46), pre-
dispose to development of familial hemolytic uremic syndrome.
Proc Natl Acad Sci USA 2003; 100:12966–71.
74 Fremeaux-Bacchi V, Dragon-Durey MA, Blouin J et al. Comple-
ment factor I: a susceptibility gene for atypical haemolytic uraemic
syndrome. J Med Genet 2004; 41:e84.
75 Kavanagh D, Kemp EJ, Mayland E et al. Mutations in complement
factor I predispose to development of atypical hemolytic uremic
syndrome. J Am Soc Nephrol 2005; 16:2150–5.
76 Goicoechea de Jorge E, Harris CL, Esparza-Gordillo J et al. Gain-
of-function mutations in complement factor B are associated with
atypical hemolytic uremic syndrome. Proc Natl Acad Sci USA 2007;
104:240–5.
77 Fremeaux-Bacchi V, Regnier C, Blouin J et al. Protective or aggres-
sive: paradoxical role of C3 in atypical hemolytic uremic syndrome.
Mol Immunol 2007; 44:172.
78 Sánchez-Corral P, Pérez-Caballero D, Huarte O et al. Structural
and functional characterization of factor H mutations associated
with atypical hemolytic uremic syndrome. Am J Hum Genet 2002;
71:1285–95.
79 Sanchez-Corral P, Gonzalez-Rubio C, Rodriguez de Cordoba S,
Lopez-Trascasa M. Functional analysis in serum from atypical
hemolytic uremic syndrome patients reveals impaired protection
of host cells associated with mutations in factor H. Mol Immunol
2004; 41:81–4.
80 Atkinson JP, Liszewski MK, Richards A, Kavanagh D, Moulton EA.
Hemolytic uremic syndrome. An example of insufficient comple-
ment regulation on self-tissue. Ann NY Acad Sci 2005; 1056:144–
52.
81 Ohali M, Shalev H, Schlesinger M et al. Hypocomplementemic
autosomal recessive hemolytic uremic syndrome with decreased
factor H. Pediatr Nephrol 1998; 12:619–24.
82 Pichette V, Querin S, Schurch W, Brun G, Lehner-Netsch G, Delage
JM. Familial hemolytic–uremic syndrome and homozygous factor
H deficiency. Am J Kidney Dis 1994; 24:936–41.
83 Rougier N, Kazatchkine MD,Rougier JP et al. Human complement
factor H deficiency associated with hemolytic uremic syndrome.
J Am Soc Nephrol 1998; 9:2318–26.
84 Thompson RA, Winterborn MH. Hypocomplementaemia due to a
genetic deficiency of beta 1H globulin. Clin Exp Immunol 1981;
46:110–19.
85 Schreiber RD, Pangburn MK, Lesavre PH, Müller-Eberhard HJ.
Initiation of the alternative pathway of complement: recognition of
activators by bound C3b and assembly of the entire pathway from
six isolated proteins. Proc Natl Acad Sci USA 1978; 75:3948–52.
86 Neumann HPH, Salzmann M, Bohnert-Iwan B et al. Haemolytic
uraemic syndrome and mutations of the factor H gene: a registry-
based study of German speaking countries. J Med Genet 2003;
40:676–81.
87 Esparza-Gordillo J, Goicoechea de Jorge E, Abarrategui Garrido C
et al. Insights into hemolytic uremic syndrome: segregation of
three independent predisposition factors in a large, multiple
affected pedigree. Mol Immunol 2006; 43:1769–75.
88 Dragon-Durey M-A, Loirat C, Cloarec S et al. Anti-factor H
autoantibodies associated with atypical hemolytic uremic
syndrome. J Am Soc Nephrol 2005; 16:555–63.
89 Jozsi M, Strobel S, Dahse HM et al. Anti factor H autoantibodies
block C-terminal recognition function of factor H in hemolytic
uremic syndrome. Blood 2007; 110:1516–18.
90 Dragon-Durey M-A, Loirat C, Ranchin B et al. Development of
anti-factor H auto-antibodies genetically predisposed in atypical
HUS. Mol Immunol 2007; 44:3922.
91 Józsi M, Strobel S, Zipfel SLH et al. Factor H autoantibodies in
atypical hemolytic uremic syndrome correlate with CFHR1/
CFHR3 deficiency and affect recognition functions. Mol Immunol
2007; 44:3024.
92 Anderson DH, Mullins RF, Hageman GS, Johnson LV. A role for
local inflammation in the formation of drusen in the aging eye.
Am J Ophthalmol 2002; 134:411–31.
TRANSLATIONAL MINI-REVIEW SERIES ON COMPLEMENT FACTOR H
S. Rodríguez de Córdoba and E. Goicoechea de Jorge
12 © 2008 The Author(s)
Journal compilation © 2008 British Society for Immunology, Clinical and Experimental Immunology,151: 1–13

93 Scholl HP, Fleckenstein M, Charbel Issa P, Keilhauer C, Holz FG,
Weber BH. An update on the genetics of age-related macular
degeneration. Mol Vis 2007; 13:196–205.
94 Rivera A, Fisher SA, Fritsche LG et al. Hypothetical LOC387715 is a
second major susceptibility gene for age-related macular degenera-
tion, contributing independently of complement factor H to
disease risk. Hum Mol Genet 2005; 14:3227–36.
95 Herbert AP, Deakin JA, Schmidt CQ et al. Structure shows
glycosaminoglycan- and protein-recognition site in factor H is per-
turbed by age-related macular degeneration-linked SNP. J Biol
Chem 2007; 282:18960–8.
96 Clark SJ, Higman VA, Mulloy B et al. His-384 allotypic variant of
factor H associated with age-related macular degeneration has dif-
ferent heparin binding properties from the non-disease-associated
form. J Biol Chem 2006; 281:24713–20.
97 Prosser BE, Johnson S, Roversi P et al. Structural basis for comple-
ment factor H linked age-related macular degeneration. J Exp Med
2007; 204:2277–83.
98 Skerka C, Lauer N, Weinberger AAWA et al. Defective complement
control of factor H (Y402H) and FHL-1 in age-related macular
degeneration. Mol Immunol 2007; 44:3398–406.
99 Laine M, Jarva H, Seitsonen S et al. Y402H polymorphism of
complement factor H affects binding affinity to C-reactive protein.
J Immunol 2007; 178:3831–6.
100 Sjoberg AP, Trouw LA, Clark SJ et al. The factor H variant
associated with age-related macular degeneration (His-384) and
the non-disease-associated form bind differentially to C-reactive
protein, fibromodulin, DNA, and necrotic cells. J Biol Chem 2007;
282:10894–900.
101 Fernández-Alonso C, Goicoechea de Jorge E,Jiménez M, Rodriguez
de Cordoba S, Germán R. Analytical ultracentrifugation analysis of
the human complement factor H variants 402His and 402Tyr.
Mol Immunol 2007; 44:3982.
102 Hakobyan S, Harris CL, van den Berg C, Pepys MB, Morgan BP.
Binding of factor H to C-reactive protein occurs only when the
latter has undergone non-physiologic denaturation. Mol Immunol
2007; 44:3983–4.
103 Li M, Atmaca-Sonmez P, Othman M et al. CFH haplotypes
without the Y402H coding variant show strong association with
susceptibility to age-related macular degeneration. Nat Genet 2006;
38:1049–54.
104 Maller J, George S, Purcell S et al. Common variation in three
genes, including a noncoding variant in CFH, strongly influences
risk of age-related macular degeneration. Nat Genet 2006;
38:1055–9.
105 Gold B, Merriam JE, Zernant J et al. Variation in factor B (BF) and
complement component 2 (C2) genes is associated with age-related
macular degeneration. Nat Genet 2006; 38:458–62.
106 Kuttner-Kondo L, Muqim N, Crabb JW, Hollyfield JG, Medof ME.
Effects on factor H function of polymorphisms linked to age-
related macular degeneration. Mol Immunol 2007; 44:201.
107 Lokki ML, Koskimies SA. Allelic differences in hemolytic activity
and protein concentration of BF molecules are found in association
with particular HLA haplotypes. Immunogenetics 1991; 34:242–6.
108 Mullins RF, Aptsiauri N, Hageman GS. Structure and composition
of drusen associated with glomerulonephritis: implications for the
role of complement activation in drusen biogenesis. Eye 2001;
15:390–5.
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