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1.  Identification of a Rare Coding Variant in Complement 3 Associated with Age-related Macular Degeneration 
Nature genetics  2013;45(11):10.1038/ng.2758.
Macular degeneration is a common cause of blindness in the elderly. To identify rare coding variants associated with a large increase in risk of age-related macular degeneration (AMD), we sequenced 2,335 cases and 789 controls in 10 candidate loci (57 genes). To increase power, we augmented our control set with ancestry-matched exome sequenced controls. An analysis of coding variation in 2,268 AMD cases and 2,268 ancestry matched controls revealed two large-effect rare variants; previously described R1210C in the CFH gene (fcase = 0.51%, fcontrol = 0.02%, OR = 23.11), and newly identified K155Q in the C3 gene (fcase = 1.06%, fcontrol = 0.39%, OR = 2.68). The variants suggest decreased inhibition of C3 by Factor H, resulting in increased activation of the alternative complement pathway, as a key component of disease biology.
PMCID: PMC3812337  PMID: 24036949
2.  Genome-wide association study of age-related macular degeneration identifies associated variants in the TNXB–FKBPL–NOTCH4 region of chromosome 6p21.3 
Human Molecular Genetics  2012;21(18):4138-4150.
Age-related macular degeneration (AMD) is a leading cause of visual loss in Western populations. Susceptibility is influenced by age, environmental and genetic factors. Known genetic risk loci do not account for all the heritability. We therefore carried out a genome-wide association study of AMD in the UK population with 893 cases of advanced AMD and 2199 controls. This showed an association with the well-established AMD risk loci ARMS2 (age-related maculopathy susceptibility 2)–HTRA1 (HtrA serine peptidase 1) (P =2.7 × 10−72), CFH (complement factor H) (P =2.3 × 10−47), C2 (complement component 2)–CFB (complement factor B) (P =5.2 × 10−9), C3 (complement component 3) (P =2.2 × 10−3) and CFI (P =3.6 × 10−3) and with more recently reported risk loci at VEGFA (P =1.2 × 10−3) and LIPC (hepatic lipase) (P =0.04). Using a replication sample of 1411 advanced AMD cases and 1431 examined controls, we confirmed a novel association between AMD and single-nucleotide polymorphisms on chromosome 6p21.3 at TNXB (tenascin XB)–FKBPL (FK506 binding protein like) [rs12153855/rs9391734; discovery P =4.3 × 10−7, replication P =3.0 × 10−4, combined P =1.3 × 10−9, odds ratio (OR) = 1.4, 95% confidence interval (CI) = 1.3–1.6] and the neighbouring gene NOTCH4 (Notch 4) (rs2071277; discovery P =3.2 × 10−8, replication P =3.8 × 10−5, combined P =2.0 × 10−11, OR = 1.3, 95% CI = 1.2–1.4). These associations remained significant in conditional analyses which included the adjacent C2–CFB locus. TNXB, FKBPL and NOTCH4 are all plausible AMD susceptibility genes, but further research will be needed to identify the causal variants and determine whether any of these genes are involved in the pathogenesis of AMD.
PMCID: PMC3428154  PMID: 22694956
3.  Genetic influences on plasma CFH and CFHR1 concentrations and their role in susceptibility to age-related macular degeneration 
Human Molecular Genetics  2013;22(23):4857-4869.
It is a longstanding puzzle why non-coding variants in the complement factor H (CFH) gene are more strongly associated with age-related macular degeneration (AMD) than functional coding variants that directly influence the alternative complement pathway. The situation is complicated by tight genetic associations across the region, including the adjacent CFH-related genes CFHR3 and CFHR1, which may themselves influence the alternative complement pathway and are contained within a common deletion (CNP147) which is associated with protection against AMD. It is unclear whether this association is mediated through a protective effect of low plasma CFHR1 concentrations, high plasma CFH or both. We examined the triangular relationships of CFH/CFHR3/CFHR1 genotype, plasma CFH or CFHR1 concentrations and AMD susceptibility in combined case–control (1256 cases, 1020 controls) and cross-sectional population (n = 1004) studies and carried out genome-wide association studies of plasma CFH and CFHR1 concentrations. A non-coding CFH SNP (rs6677604) and the CNP147 deletion were strongly correlated both with each other and with plasma CFH and CFHR1 concentrations. The plasma CFH-raising rs6677604 allele and raised plasma CFH concentration were each associated with AMD protection. In contrast, the protective association of the CNP147 deletion with AMD was not mediated by low plasma CFHR1, since AMD-free controls showed increased plasma CFHR1 compared with cases, but it may be mediated by the association of CNP147 with raised plasma CFH concentration. The results are most consistent with a regulatory locus within a 32 kb region of the CFH gene, with a major effect on plasma CFH concentration and AMD susceptibility.
PMCID: PMC3820139  PMID: 23873044
5.  Evidence of association of APOE with age-related macular degeneration - a pooled analysis of 15 studies 
Human mutation  2011;32(12):1407-1416.
Age-related macular degeneration (AMD) is the most common cause of incurable visual impairment in high-income countries. Previous studies report inconsistent associations between AMD and apolipoprotein E (APOE), a lipid transport protein involved in low-density cholesterol modulation. Potential interaction between APOE and sex, and smoking status, has been reported. We present a pooled analysis (n=21,160) demonstrating associations between late AMD and APOε4 (OR=0.72 per haplotype; CI: 0.65–0.74; P=4.41×10−11) and APOε2 (OR=1.83 for homozygote carriers; CI: 1.04–3.23; P=0.04), following adjustment for age-group and sex within each study and smoking status. No evidence of interaction between APOE and sex or smoking was found. Ever smokers had significant increased risk relative to never smokers for both neovascular (OR=1.54; CI: 1.38–1.72; P=2.8×10−15) and atrophic (OR=1.38; CI: 1.18–1.61; P=3.37×10−5) AMD but not early AMD (OR=0.94; CI: 0.86–1.03; P=0.16), implicating smoking as a major contributing factor to disease progression from early signs to the visually disabling late forms. Extended haplotype analysis incorporating rs405509 did not identify additional risks beyondε2 and ε4 haplotypes. Our expanded analysis substantially improves our understanding of the association between the APOE locus and AMD. It further provides evidence supporting the role of cholesterol modulation, and low-density cholesterol specifically, in AMD disease etiology.
PMCID: PMC3217135  PMID: 21882290
age-related macular degeneration; AMD; apolipoprotein E; APOE; case-control association study
6.  Complement Factor D in Age-Related Macular Degeneration 
Complement factor D catalyzes a critical step in the alternative complement activation pathway. The authors report a significant elevation in plasma CFD concentrations in age-related macular degeneration (AMD) patients compared with controls and a weak genetic association between CFD gene variants and AMD.
To examine the role of complement factor D (CFD) in age-related macular degeneration (AMD) by analysis of genetic association, copy number variation, and plasma CFD concentrations.
Single nucleotide polymorphisms (SNPs) in the CFD gene were genotyped and the results analyzed by binary logistic regression. CFD gene copy number was analyzed by gene copy number assay. Plasma CFD was measured by an enzyme-linked immunosorbent assay.
Genetic association was found between CFD gene SNP rs3826945 and AMD (odds ratio 1.44; P = 0.028) in a small discovery case-control series (462 cases and 325 controls) and replicated in a combined cohorts meta-analysis of 4765 cases and 2693 controls, with an odds ratio of 1.11 (P = 0.032), with the association almost confined to females. Copy number variation in the CFD gene was identified in 13 out of 640 samples examined but there was no difference in frequency between AMD cases (1.3%) and controls (2.7%). Plasma CFD concentration was measured in 751 AMD cases and 474 controls and found to be elevated in AMD cases (P = 0.00025). The odds ratio for those in the highest versus lowest quartile for plasma CFD was 1.81. The difference in plasma CFD was again almost confined to females.
CFD regulates activation of the alternative complement pathway, which is implicated in AMD pathogenesis. The authors found evidence for genetic association between a CFD gene SNP and AMD and a significant increase in plasma CFD concentration in AMD cases compared with controls, consistent with a role for CFD in AMD pathogenesis.
PMCID: PMC3230905  PMID: 22003108
7.  Genetic variation in complement regulators and susceptibility to age-related macular degeneration 
Immunobiology  2012;217(2):158-161.
Age-related macular degeneration (AMD) is the commonest cause of blindness in Western populations. Risk is influenced by age, genetic and environmental factors. Complement activation appears to be important in the pathogenesis and associations have been found between AMD and genetic variations in complement regulators such as complement factor H. We therefore investigated other complement regulators for association with AMD.
We carried out a case–control study to test for association between AMD and single nucleotide polymorphisms (SNPs) spanning the genes encoding complement factor P (CFP, properdin), CD46 (membrane cofactor protein, MCP), CD55 (decay accelerating factor, DAF) and CD59 (protectin). All cases and controls were examined by an ophthalmologist and had independent grading of fundus photographs to confirm their disease status.
20 SNPs were genotyped in 446 cases and 262 controls. For two SNPs with p-values approaching significance additional subjects were genotyped to increase the numbers to 622 cases and 359 controls. There was no evidence of association between AMD and any of the SNPs typed in CFP, CD46, CD55 or CD59.
In a case–control sample that has shown the well established associations between AMD and variants in CFH, CFB and C3 there was absence of association with SNPs in CFP, CD46, CD55 and CD59. This suggests that these are not important susceptibility genes for AMD.
PMCID: PMC3657157  PMID: 22024702
AMD, age-related macular degeneration; ARM, age-related maculopathy; CFB, complement factor B; CFH, complement factor H; CI, confidence interval; CPI, complement factor I; CFP, complement factor P; CNV, choroidal neovascularisation; DAF, decay accelerating factor; DNA, deoxyribonucleic acid; GA, geographic atrophy; HWE, Hardy–Weinberg equilibrium; MAC, membrane attack complex; MAF, minor allele frequency; MCP, membrane cofactor protein; OR, odds ratio; RPE, retinal pigment epithelium; SNP, single nucleotide polymorphism; Age-related macular degeneration; Complement; Complement regulators; Genetic association; Genetic variation; Single nucleotide polymorphism
9.  Germline Mutation in NLRP2 (NALP2) in a Familial Imprinting Disorder (Beckwith-Wiedemann Syndrome) 
PLoS Genetics  2009;5(3):e1000423.
Beckwith-Wiedemann syndrome (BWS) is a fetal overgrowth and human imprinting disorder resulting from the deregulation of a number of genes, including IGF2 and CDKN1C, in the imprinted gene cluster on chromosome 11p15.5. Most cases are sporadic and result from epimutations at either of the two 11p15.5 imprinting centres (IC1 and IC2). However, rare familial cases may be associated with germline 11p15.5 deletions causing abnormal imprinting in cis. We report a family with BWS and an IC2 epimutation in which affected siblings had inherited different parental 11p15.5 alleles excluding an in cis mechanism. Using a positional-candidate gene approach, we found that the mother was homozygous for a frameshift mutation in exon 6 of NLRP2. While germline mutations in NLRP7 have previously been associated with familial hydatidiform mole, this is the first description of NLRP2 mutation in human disease and the first report of a trans mechanism for disordered imprinting in BWS. These observations are consistent with the hypothesis that NLRP2 has a previously unrecognised role in establishing or maintaining genomic imprinting in humans.
Author Summary
A small set of genes (imprinted genes) are expressed in a “parent-of-origin” manner, a phenomenon known as genomic imprinting. Research in human disorders associated with aberrant genomic imprinting provided insights into the molecular mechanisms of genomic imprinting and the role of imprinted genes in normal growth and development. Beckwith-Wiedemann syndrome (BWS) is a congenital overgrowth syndrome associated with developmental abnormalities and a predisposition to embryonic tumours. BWS results from alterations in expression or function of imprinted genes in the imprinted gene cluster at chromosome 11p15. Although BWS may be caused by a variety of molecular mechanisms, to date, all the genetic and epigenetic defects associated with BWS have been limited to 11p15.5. We report a family with two children affected with BWS and an epigenetic defect at 11p15.5 in which the primary genetic defect mapped outside the imprinted gene cluster. Using autozygosity mapping, we found an extended homozygous region on chromosome 19q13.4 (containing NLRP2 and NLRP7 genes) in the mother. Homozygous inactivating mutations in NLRP7 in women have been associated previously with abnormal imprinting and recurrent hydatidiform moles. We identified a homozygous frameshift mutation in NLRP2 in the mother of the two children with BWS implicating NLRP2 in the establishment and/or maintenance of genomic imprinting/methylation.
PMCID: PMC2650258  PMID: 19300480

Results 1-10 (10)