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1.  Prevalence in the General Population of a CFH Sequence Variant Associated with Atypical Haemolytic Uraemic Syndrome in an Extensive Family from Southwest England 
Nephron Extra  2013;3(1):86-90.
Background/Aims
Twenty-five members of a family from the county of Devon in England have been affected by atypical haemolytic uraemic syndrome (aHUS) associated with a CFH mutation (c.3643C>G; p.Arg1215Gly). A 65-year-old male was diagnosed with aHUS after losing a renal transplant to a thrombotic microangiopathy. Subsequent mutation screening revealed the same CFH mutation without him being knowingly related to the local kindred. We designed a study to investigate the prevalence of this mutation in the local area. In addition, we examined the diagnoses of pre-existing haemodialysis patients to determine whether other patients might unknowingly be at risk of carrying the same CFH mutation.
Methods
The Exeter Ten Thousand (EXTEND) study aims to recruit 10,000 healthy volunteers over the age of 18 years living within 25 miles of Exeter in Devon. We genotyped DNA from 4,000 EXTEND subjects for CFH c.3643C>G; p.Arg1215Gly. We reviewed the diagnoses of 294 haemodialysis patients in the Devon area and genotyped 7 patients with either end-stage renal disease of unknown aetiology, malignant hypertension or renovascular disease.
Results
CFH c.3643C>G; p.Arg1215Gly was not detected in any of the 7 haemodialysis patients or the 4,000 individuals within the EXTEND study.
Conclusions
We conclude that CFH c.3643C>G; p.Arg1215Gly is not endemic in Devon. This reinforces our existing practice of genotyping only patients with kidney disease and evidence of a thrombotic microangiopathy for this mutation. This is the first study looking at the prevalence of CFH mutations in the general population.
doi:10.1159/000354667
PMCID: PMC3806708  PMID: 24163689
Atypical haemolytic uraemic syndrome; CFH; Thrombotic microangiopathy; Transplantation

2.  Common genetic variants in complement genes other than CFH, CD46 and the CFHRs are not associated with aHUS 
Molecular Immunology  2012;49(4):640-648.
Highlights
► Hypothesis tested: common sequence variants in complement are associated with aHUS. ► SNPs in complement genes were genotyped in two independent aHUS cohorts. ► Only SNPs within CFH, CD46 and the CFHRs showed a replicable association with aHUS. ► Complement regulators variability has the main role in determining the disease.
It is well established that common genetic variants in CFH, CD46 and the CFHRs are additional risk factors for the development of aHUS. To examine the hypothesis that common variants in other complement genes have a similar effect we genotyped 501 SNPs in 47 complement genes in 94 aHUS patients from Newcastle, 126 aHUS patients from Paris, 374 UK controls and 165 French controls. We replicated the associations in CFH, CD46 and the CFHRs but found no association with any other complement gene. The strongest associations replicated in both cohorts were found for four SNPs within CD46 (p-value < 10−3) and five SNPs within CFH (p-value <5 × 10−3). Significant replicable associations with single SNPs in CFHR2, CFHR4 and an intergenic SNP (CR1–CD46) were also found. Analysis of the Paris cohort showed that the association with CD46 SNPs was only present in those patients with complement mutations. Haplotype analysis showed at-risk and protective haplotypes in both CD46 and CFH. The CD46 haplotype was only disease-associated in those patients with mutations.
doi:10.1016/j.molimm.2011.11.003
PMCID: PMC3438446  PMID: 22153652
aHUS; Complement; Genetic polymorphisms
4.  Modeling How CD46 Deficiency Predisposes to Atypical Hemolytic Uremic Syndrome 
Molecular immunology  2006;44(7):1559-1568.
Mutations in complement regulatory proteins predispose to the development of aHUS. Approximately 50% of patients bear a mutation in one of three complement control proteins, factor H, factor I, or membrane cofactor protein (MCP; CD46). Another membrane regulator that is closely related to MCP, decay accelerating factor (DAF; CD55) thus far has shown no association with aHUS and continues to be investigated. The goal of this study was to compare the regulatory profile of MCP and DAF and to assess how alterations in MCP predispose to complement dysregulation. We employed a model system of complement activation on Chinese hamster ovary (CHO) cell transfectants. The four regularly expressed isoforms of MCP and DAF inhibited C3b deposition by the alternative pathway. DAF, but not MCP, inhibited the classical pathway. Most patients with MCP-aHUS are heterozygous and express only 25–50 % of the wild-type protein. We, therefore, analyzed the effect of reduced levels of wild-type MCP and found that cells with lowered expression levels were less efficient in inhibiting alternative pathway activation. Further, a dysfunctional MCP mutant, expressed at normal levels and identified in five patients with aHUS (S206P), failed to protect against C3b amplification on CHO cells, even if expression levels were increased 10-fold. Our results add new information relative to the necessity for appropriate expression levels of MCP and further implicate the alternative pathway in disease processes such as aHUS.
doi:10.1016/j.molimm.2006.08.024
PMCID: PMC1828070  PMID: 17027083
Hemolytic uremic syndrome; complement; CD46; MCP; CD55; DAF; alternative pathway of complement
5.  Complement factor H and the hemolytic uremic syndrome 
The Journal of Experimental Medicine  2007;204(6):1245-1248.
Immune recognition is coupled to powerful proinflammatory effector pathways that must be tightly regulated. The ancient alternative pathway of complement activation is one such proinflammatory pathway. Genetic susceptibility factors have been identified in both regulators and activating components of the alternative pathway that are associated with thrombotic microangiopathies, glomerulonephritides, and chronic conditions featuring debris deposition. These observations indicate that excessive alternative pathway activation promotes thrombosis in the microvasculature and tissue damage during debris accumulation. Intriguingly, distinct genetic changes in factor H (FH), a key regulator of the alternative pathway, are associated with hemolytic uremic syndrome (HUS), membranoproliferative glomerulonephritis (dense deposit disease), or age-related macular degeneration (AMD). A mouse model of HUS designed to mirror human mutations in FH has now been developed, providing new understanding of the molecular pathogenesis of complement-related endothelial disorders.
doi:10.1084/jem.20070664
PMCID: PMC2118604  PMID: 17548524
6.  Determining the Population Frequency of the CFHR3/CFHR1 Deletion at 1q32 
PLoS ONE  2013;8(4):e60352.
In this study we have used multiplex ligation-dependent probe amplification (MLPA) to measure the copy number of CFHR3 and CFHR1 in DNA samples from 238 individuals from the UK and 439 individuals from the HGDP-CEPH Human Genome Diversity Cell Line Panel. We have then calculated the allele frequency and frequency of homozygosity for the copy number polymorphism represented by the CFHR3/CFHR1 deletion. There was a highly significant difference between geographical locations in both the allele frequency (X2 = 127.7, DF = 11, P-value = 4.97x10-22) and frequency of homozygosity (X2 = 142.3, DF = 22, P-value = 1.33x10-19). The highest frequency for the deleted allele (54.7%) was seen in DNA samples from Nigeria and the lowest (0%) in samples from South America and Japan. The observed frequencies in conjunction with the known association of the deletion with AMD, SLE and IgA nephropathy is in keeping with differences in the prevalence of these diseases in African and European Americans. This emphasises the importance of identifying copy number polymorphism in disease.
doi:10.1371/journal.pone.0060352
PMCID: PMC3629053  PMID: 23613724
7.  Deletion of Complement Factor H–Related Genes CFHR1 and CFHR3 Is Associated with Atypical Hemolytic Uremic Syndrome 
PLoS Genetics  2007;3(3):e41.
Atypical hemolytic uremic syndrome (aHUS) is associated with defective complement regulation. Disease-associated mutations have been described in the genes encoding the complement regulators complement factor H, membrane cofactor protein, factor B, and factor I. In this study, we show in two independent cohorts of aHUS patients that deletion of two closely related genes, complement factor H–related 1 (CFHR1) and complement factor H–related 3 (CFHR3), increases the risk of aHUS. Amplification analysis and sequencing of genomic DNA of three affected individuals revealed a chromosomal deletion of ∼84 kb in the RCA gene cluster, resulting in loss of the genes coding for CFHR1 and CFHR3, but leaving the genomic structure of factor H intact. The CFHR1 and CFHR3 genes are flanked by long homologous repeats with long interspersed nuclear elements (retrotransposons) and we suggest that nonallelic homologous recombination between these repeats results in the loss of the two genes. Impaired protection of erythrocytes from complement activation is observed in the serum of aHUS patients deficient in CFHR1 and CFHR3, thus suggesting a regulatory role for CFHR1 and CFHR3 in complement activation. The identification of CFHR1/CFHR3 deficiency in aHUS patients may lead to the design of new diagnostic approaches, such as enhanced testing for these genes.
Author Summary
Hemolytic uremic syndrome (HUS) is a severe kidney disease, which is characterized by hemolytic anemia, thrombocytopenia, and acute renal failure. The nondiarrhea-associated form, also known as atypical HUS (aHUS), is rare, sometimes familial, often recurrent, and has a poor outcome. Several studies have shown that aHUS is associated with mutations in genes coding for complement regulators, which leads to defective regulation of complement activation, particularly at cell surfaces. We report a novel susceptibility factor for aHUS in the form of a chromosomal deletion of a large (∼84 kb) genomic fragment in the regulators of complement activation gene cluster at Chromosome 1q32. This deletion is a result of nonallelic homologous recombination and leads to the loss of two genes, CFHR1 and CFHR3, which encode factor H–related proteins 1 and 3, respectively. We recommend diagnostic screening of aHUS patients for these susceptibility factors.
doi:10.1371/journal.pgen.0030041
PMCID: PMC1828695  PMID: 17367211
8.  Deletion of Complement Factor H–Related Genes CFHR1 and CFHR3 Is Associated with Atypical Hemolytic Uremic Syndrome 
PLoS Genetics  2007;3(3):e41.
Atypical hemolytic uremic syndrome (aHUS) is associated with defective complement regulation. Disease-associated mutations have been described in the genes encoding the complement regulators complement factor H, membrane cofactor protein, factor B, and factor I. In this study, we show in two independent cohorts of aHUS patients that deletion of two closely related genes, complement factor H–related 1 (CFHR1) and complement factor H–related 3 (CFHR3), increases the risk of aHUS. Amplification analysis and sequencing of genomic DNA of three affected individuals revealed a chromosomal deletion of ∼84 kb in the RCA gene cluster, resulting in loss of the genes coding for CFHR1 and CFHR3, but leaving the genomic structure of factor H intact. The CFHR1 and CFHR3 genes are flanked by long homologous repeats with long interspersed nuclear elements (retrotransposons) and we suggest that nonallelic homologous recombination between these repeats results in the loss of the two genes. Impaired protection of erythrocytes from complement activation is observed in the serum of aHUS patients deficient in CFHR1 and CFHR3, thus suggesting a regulatory role for CFHR1 and CFHR3 in complement activation. The identification of CFHR1/CFHR3 deficiency in aHUS patients may lead to the design of new diagnostic approaches, such as enhanced testing for these genes.
Author Summary
Hemolytic uremic syndrome (HUS) is a severe kidney disease, which is characterized by hemolytic anemia, thrombocytopenia, and acute renal failure. The nondiarrhea-associated form, also known as atypical HUS (aHUS), is rare, sometimes familial, often recurrent, and has a poor outcome. Several studies have shown that aHUS is associated with mutations in genes coding for complement regulators, which leads to defective regulation of complement activation, particularly at cell surfaces. We report a novel susceptibility factor for aHUS in the form of a chromosomal deletion of a large (∼84 kb) genomic fragment in the regulators of complement activation gene cluster at Chromosome 1q32. This deletion is a result of nonallelic homologous recombination and leads to the loss of two genes, CFHR1 and CFHR3, which encode factor H–related proteins 1 and 3, respectively. We recommend diagnostic screening of aHUS patients for these susceptibility factors.
doi:10.1371/journal.pgen.0030041
PMCID: PMC1828695  PMID: 17367211
9.  Atypical Haemolytic Uraemic Syndrome Associated with a Hybrid Complement Gene 
PLoS Medicine  2006;3(10):e431.
Background
Sequence analysis of the regulators of complement activation (RCA) cluster of genes at chromosome position 1q32 shows evidence of several large genomic duplications. These duplications have resulted in a high degree of sequence identity between the gene for factor H (CFH) and the genes for the five factor H-related proteins (CFHL1–5; aliases CFHR1–5). CFH mutations have been described in association with atypical haemolytic uraemic syndrome (aHUS). The majority of the mutations are missense changes that cluster in the C-terminal region and impair the ability of factor H to regulate surface-bound C3b. Some have arisen as a result of gene conversion between CFH and CFHL1. In this study we tested the hypothesis that nonallelic homologous recombination between low-copy repeats in the RCA cluster could result in the formation of a hybrid CFH/CFHL1 gene that predisposes to the development of aHUS.
Methods and Findings
In a family with many cases of aHUS that segregate with the RCA cluster we used cDNA analysis, gene sequencing, and Southern blotting to show that affected individuals carry a heterozygous CFH/CFHL1 hybrid gene in which exons 1–21 are derived from CFH and exons 22/23 from CFHL1. This hybrid encodes a protein product identical to a functionally significant CFH mutant (c.3572C>T, S1191L and c.3590T>C, V1197A) that has been previously described in association with aHUS.
Conclusions
CFH mutation screening is recommended in all aHUS patients prior to renal transplantation because of the high risk of disease recurrence post-transplant in those known to have a CFH mutation. Because of our finding it will be necessary to implement additional screening strategies that will detect a hybrid CFH/CFHL1 gene.
Tim Goodship and colleagues have identified a heterozygousCFH/CFHL1 hybrid gene which encodes a protein product identical to one previously described in association with atypical hemolytic uremic syndrome.
Editors' Summary
Background.
Atypical hemolytic uremic (aHUS) syndrome is a rare, chronic disease that can run in families. People with the condition are prone to developing kidney failure and high blood pressure, and are likely to have a shorter life span than healthy people. Previous work done by a group of researchers in Newcastle-on-Tyne, UK looked at the genetic underpinnings of aHUS in three families suffering from the condition. They found a region of the genome that was linked with the disease in all three families. That region was known to contain a gene for a protein called “factor H,” as well as a number of other genes for proteins that are involved in the same pathway as factor H in controlling an ancient defence system called complement. This system helps antibodies to kill invaders by marking any cell that is not protected by proteins such as factor H. Our own cells would be under constant threat without protective proteins such as factor H. Later studies found simple genetic mutations in people with aHUS, in the genes coding for factor H. However, other work suggested that in some families with aHUS, simple genetic mutations might not be the cause; instead more complicated rearrangements of the genome might occur which would then result in an abnormal factor H that incorporated part of the gene for another protective protein called factor H related protein 1.
Why Was This Study Done?
The researchers knew that it was important to understand the exact genetic mutations linked with aHUS in different families. This was because the exact type of mutation would help them predict whether a kidney transplant is likely to be successful in treating an individual with aHUS who has developed kidney failure. In people with mutations affecting proteins produced by the kidney, a kidney transplant would be likely to work; but in people with mutations affecting factor H, which is produced by the liver, the disease would probably recur after a kidney transplant.
What Did the Researchers Do and Find?
In this study, the researchers went back to one of the three families with aHUS they had previously studied. The researchers had shown before that in this family, the disease was linked with the genome region containing factor H, but no precise mutation in that region had been found. This time, the researchers screened the genome of the family members and looked in particular for a specific rearrangement of the genome that they suspected might be involved. They found that the genomes in this family had been shuffled in the factor H region, resulting in an abnormal version of factor H being produced.
What Do These Findings Mean?
The mutation these researchers identified is likely to result in development of aHUS that does not get better after a kidney transplant, because the abnormal factor H would still be produced in the liver after a transplant had been done. Therefore, the researchers suggest that patients with aHUS be checked for this particular mutation before it is decided whether to go ahead with a transplant.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0030431.
US National Institutes of Health Office of Rare Diseases information about atypical hemolytic uremic syndrome
The Online Mendelian Inheritance in Man (OMIM) contains an entry on hemolytic uremic syndrome. OMIM is a database of human genes and genetic disorders developed by the US National Center for Biotechnology Information
The US National Kidney and Urologic Diseases has a page about hemolytic uremic syndrome
The Wikipedia has a page about HUS (note that Wikipedia is a free online encyclopedia that anyone can edit)
doi:10.1371/journal.pmed.0030431
PMCID: PMC1626556  PMID: 17076561

Results 1-9 (9)