Variation in complement component C1 inhibitor in age-related macular degeneration

This study assessed variation in plasma levels of the complement regulatorC1 inhibitor (C1inh) in patients with age related macular degeneration (AMD) and controls. Plasma from391 AMD cases and 370 controls was assayed by rate nephelometry to determine C1inh protein levels. Protein levels were analysed for relationships with age, gender, smoking, AMD disease status and genetic variation in the SERPING1 gene, which encodes C1inh, using a multivariate analysis. t-Tests show a significant difference in C1inh levels in AMD cases compared with controls (p=2.340E-6), smokers compared to non-smokers (p=1.022E-4) and females compared to males (p=1.661E-7). Multivariate analysis shows that after accounting for gender and smoking AMD status remained significant. Age was included in the model but was not significant. Including genetic variation in the model shows that one significant SNP (rs2649663) 5' of the SERPING1 gene is associated with C1inh levels though this SNP is not associated with AMD. This suggests that genetic variation in the promoter region of the SERPING1 gene may influence expression of the gene.

Age-related macular degeneration and the complement system

Age-related macular degeneration (AMD) is the leading cause of blindness in the developed world. It is a complex multifactorial disease, and despite new advances in treatment, many patients still succumb to visual impairment. The complement pathway has been implicated in the pathogenesis of many diseases, and recently variants in several genes encoding complement pathway proteins have been associated with AMD. Complement proteins have been found in histological specimens of eyes with AMD. Altered levels of both intrinsic complement proteins and activated products have been found in the circulation of patients with AMD. Complement activation may be triggered by oxidative stress, resulting from retinal exposure to incoming light; indeed an inter-play between these two pathological processes seems to exist. Finally, complement inhibitors are currently being evaluated in clinical trials. This article reviews the role of the complement system in AMD, and the potential of complement inhibition in preventing the devastating blindness resulting from this disease.

X-linked retinoschisis maculopathy treated with topical dorzolamide, and relationship to genotype

PURPOSE

To correlate the response of topical dorzolamide (Trusopt; Merck) in patients with X-linked retinoschisis (XLRS) with genotype.

METHODS

We carried out a retrospective evaluation of four patients (seven eyes) with XLRS, treated with topical dorzolamide. The change in best-corrected visual acuity (VA) and central macular thickness (CMT; central 1 mm subfield thickness) from optical coherence tomography (OCT) was analysed over the follow-up period, using Student's t-test. Each patient also had genetic analysis for mutations in the retinoschisisgene (RS1).

RESULTS

The mean age at the start of treatment was 14.7±11 years, and mean follow-up duration was 21.7±7.7 months. Mean CMT at the final follow-up was significantly better than at baseline (291±123 vs 352±119 μm, P=0.007); however, mean VA was worse (0.38±0.25 vs 0.31±0.24 logMAR score, P=0.041). All four patients had a mutation in the RS1gene; there was no apparent association between the type of mutation and the response to topical dorzolamide.

CONCLUSION

Topical dorzolamide may have some effect in reducing central macular thickness in patients with XLRS, but this does not necessarily correlate with improvement in VA. In our case series, genotypic information did not predict the response to this treatment.

Interleukin-8 promoter polymorphism -251A/T is a risk factor for age-related macular degeneration

BACKGROUND/AIMS

To determine whether four expression-related cytokine polymorphisms are associated with age-related macular degeneration (AMD).

METHODS

DNA from 478 cases with AMD and 555 normal controls was genotyped for the pro-inflammatory IL1beta -511C/T, IL6 -174C/G, IL8 -251A/T and anti-inflammatory IL10 -1082G/A cytokine polymorphisms using the 5' nuclease TaqMan(R) assay for allelic discrimination. Associations with AMD were analysed using allelic frequencies.

RESULTS

The -251A allele of the IL8 promoter gene polymorphism was more prevalent in AMD patients than controls (p = 0.037, OR = 1.21, 95% CI = 1.01 to 1.44). Adjusting for age, sex, body mass index (BMI), current smoking and past smoking status did not alter the AMD association significantly (corrected p value = 0.043, OR = 1.23, 95% CI = 1.0 to 1.50).

CONCLUSION

The pro-inflammatory homozygous IL8 -251AA genotype is an important risk factor for AMD. This may have implications for future therapy with biological agents that could target this cytokine.

An analysis of the CFH Y402H genotype in AMD patients and controls from the UK, and response to PDT treatment

AIM

Mutation in the complement factor H (CFH) gene is an important risk factor for age-related macular degeneration (AMD). In this study, we identified the strength of the CFH Y402H gene variant association in a UK AMD cohort and tested the hypothesis that this variant may influence the biological response of choroidal neovascularisation (CNV) following photodynamic therapy (PDT) for CNV.

METHODS

A total of 557 cases with AMD and 551 normal controls were genotyped for the CFH Y402H (1277 C/T) variant using the 5' nuclease TaqMan assay for allelic discrimination. The CFH gene association for AMD, for the different CNV subtypes and for patients needing PDT was estimated. Twenty-seven PDT-treated patients were followed up for 15 months with ETDRS-derived vision, clinical examination, and fundus angiography. Individuals with different CFH genotypes were then analysed for any association with visual change following PDT.

RESULTS

The risk association for AMD with the CFH CC genotype (odd ratio (OR)=3.62, Pc<0.0001) was similar to that reported in other Caucasian cohorts. The magnitude and strength of this association was stronger in AREDS stages 2-4 (ORs=4.48, 2.69, and 5.17). ORs for the risk of predominantly classic CNV were significantly raised for both the CC (OR=17.87, P<0.0001) and CT (OR=9.06, P=0.0002) genotypes. The number of patients carrying the high-risk C allele was 70.4% in those requiring PDT as compared to 52.3% in the non-PDT group (OR=2.16, P=0.011), and presence of the CC genotype significantly increased the risk of PDT (OR=5.48, P=0.015). The degree of visual loss following PDT was significantly higher in the CFH CC genotype group (P=0.038); 50% of CC cases (n=13) and 45% of the CT cases (n=12) lost 15 or more ETDRS letters at final follow-up.

CONCLUSION

In this UK cohort of AMD patients, the CFH Y402H variant was significantly enriched in patients with predominantly classic CNV. Patients homozygous for the CFH Y402H genotype seem to have worse visual acuity after PDT.

HLA and eye disease: a synopsis

Human leukocyte antigen (HLA) gene products have been implicated in the pathogenesis of an increasing number of eye diseases, mainly inflammatory in nature. This perspective reviews the current hypotheses for why HLA polymorphisms are associated with specific eye diseases. Statistical problems in studies involving HLA associations are discussed, and possible solutions outlined. The relevance of HLA testing in routine ophthalmic practice, its practical and cost implications is also assessed.

CRB1 mutations may result in retinitis pigmentosa without para-arteriolar RPE preservation

PURPOSE

To report a new phenotype in retinitis pigmentosa (RP) patients with CRB1 mutations at the RP12 locus.

PATIENTS

Thirty-seven patients from two Pakistani families with severe retinitis pigmentosa.

METHODS

Samples were screened with single-strand conformation polymorphism analysis followed by DNA sequencing of the coding sequence of the CRB1 gene.

RESULTS

Two novel CRB1 mutations were discovered. No patients had evidence of preservation of the para-arteriolar retinal pigment epithelium (PPRPE) that has been previously reported in all cases of RP associated with CRB1 mutations.

CONCLUSIONS

Patients with severe autosomal recessive (or simplex) RP who lack the finding of PPRPE should not be excluded from molecular analysis of CRB1 purely because they lack the clinical feature of PPRPE. This report illustrates that RP at the RP12 locus is not clinically uniform. The absence of PPRPE cannot be used to exclude CRB1 as a potential molecular explanation for RP.

Variation of codons 1961 and 2177 of the Stargardt disease gene is not associated with age-related macular degeneration

OBJECTIVES

To investigate the role of 2 specific alleles of the Stargardt disease gene (ABCA4) in the pathogenesis of age-related macular degeneration (AMD). Secondary objectives were to investigate differences in frequency of the G1961E allele in selected ethnic groups as well as to examine the segregation of both G1961E and D2177N alleles in 5 multiplex families with AMD.

METHODS

Five hundred forty-four patients with AMD and 689 controls were ascertained from 3 continents. Blood samples from 62 normal individuals of Somalian ancestry were also obtained. Participants were screened for the presence of these ABCA4 alleles with a combination of restriction digestion and single-strand conformation polymorphism analysis of polymerase chain reaction amplification products. Detected alleles were confirmed by DNA sequencing. The number of subjects exhibiting the G1961E or D2177N variants were compared between AMD and control groups using a 2-tailed Fisher exact test.

RESULTS

There was no significant difference (P >.1) in the frequency of the G1961E and D2177N alleles in patients with AMD (2.2%) vs controls (1.0%). In contrast, there was a significant difference (P< .001) in the frequency of the G1961E alleles between normal individuals of Somali ancestry (11.3%) and normal individuals from other populations (0.4%). There was no evidence of cosegregation of these alleles and the AMD phenotype in the 5 multiplex families with AMD examined. These two ABCA4 alleles were slightly more frequent in patients with AMD with choroidal neovascularization (2.7%) than those without this complication (2.5%).

CONCLUSIONS

Somali ancestry is more than 100 times more strongly associated with presence of the G1961E allele than the AMD phenotype. This study did not find any statistically significant evidence for involvement of the G1961E or D2177N alleles of the ABCA4 gene in AMD.

CLINICAL RELEVANCE

The ABCA4 gene is definitively involved in the pathogenesis of Stargardt disease and some cases of photoreceptor degeneration. However, it does not seem to be involved in a statistically significant fraction of AMD cases.

An analysis of allelic variation in the ABCA4 gene

PURPOSE

To assess the allelic variation of the ATP-binding transporter protein (ABCA4).

METHODS

A combination of single-strand conformation polymorphism (SSCP) and automated DNA sequencing was used to systematically screen this gene for sequence variations in 374 unrelated probands with a clinical diagnosis of Stargardt disease, 182 patients with age-related macular degeneration (AMD), and 96 normal subjects.

RESULTS

There was no significant difference in the proportion of any single variant or class of variant between the control and AMD groups. In contrast, truncating variants, amino acid substitutions, synonymous codon changes, and intronic variants were significantly enriched in patients with Stargardt disease when compared with their presence in subjects without Stargardt disease (Kruskal-Wallis P < 0.0001 for each variant group). Overall, there were 2480 instances of 213 different variants in the ABCA4 gene, including 589 instances of 97 amino acid substitutions, and 45 instances of 33 truncating variants.

CONCLUSIONS

Of the 97 amino acid substitutions, 11 occurred at a frequency that made them unlikely to be high-penetrance recessive disease-causing variants (HPRDCV). After accounting for variants in cis, one or more changes that were compatible with HPRDCV were found on 35% of all Stargardt-associated alleles overall. The nucleotide diversity of the ABCA4 coding region, a collective measure of the number and prevalence of polymorphic sites in a region of DNA, was found to be 1.28, a value that is 9 to 400 times greater than that of two other macular disease genes that were examined in a similar fashion (VMD2 and EFEMP1).

Mutations in the CRB1 gene cause Leber congenital amaurosis

OBJECTIVES

To test the hypothesis that mutations in the CRB1 gene cause Leber congenital amaurosis (LCA) and, if so, to describe the ocular phenotype of patients with LCA who harbor CRB1 sequence variations.

PATIENTS

One hundred ninety probands with a clinical diagnosis of LCA were selected from a cohort of 233 probands ascertained in 5 different countries. The remaining 43 probands (18%) were excluded because they harbored sequence variations in previously identified LCA genes.

METHODS

One hundred ninety unrelated individuals with LCA were screened for coding sequence mutations in the CRB1 gene with single-strand conformation polymorphism analysis followed by automated DNA sequencing.

RESULTS

Twenty-one of the 190 probands (9% of the total cohort of 233) and 2 (1.4%) of 140 controls harbored amino acid-altering sequence variations in the CRB1 gene (P =.003).

CONCLUSIONS

In our cohort of patients with LCA, coding sequence variations were observed in the CRB1 gene more frequently than in any of the other 5 known LCA-associated genes. Likely disease-causing sequence variations have now been identified in 64 (28%) of 233 subjects in this cohort.

CLINICAL RELEVANCE

Molecular diagnosis can confirm and clarify the diagnosis in an increasing fraction of patients with LCA. As genotype data accumulate, clinical phenotypes associated with specific mutations may be established. This will facilitate the counseling of patients regarding their visual prognosis and the likelihood of associated systemic anomalies.

Electrophysiology findings in a large family with central areolar choroidal dystrophy

PURPOSE

To perform an electrophysiological study of central areolar choroidal dystrophy (CACD) in the affected members of a four generation family.

METHODS

Eight affected family members from the last three generations of a family affected by CACD were assessed by full-field electroretinograms (rod response, maximal combined response, oscillatory potentials, single-flash cone response and 30 Hz flicker responses) and electro-oculograms. In addition three members of the youngest generation, who were visually asymptomatic, had pattern visual evoked potentials (PVEPs) and pattern electroretinograms (PERGs) performed. Affected status had been determined previously by genetic analysis.

RESULTS

Three youngest generation family members, who were considered affected by genetic haplotype analysis, had no visible optic nerve or retinal abnormalities. All of these subjects had abnormal PVEPs and PERGs in both eyes. Abnormalities were also detected in two of these subject's Rod ERGs, Cone ERGs and one of these subject's Maximal ERGs and 30 Hz ERGs. Electrophysiological examination in the older generations demonstrated a similar, more advanced, cone and rod dysfunction.

CONCLUSIONS

All affected, but clinically normal, youngest generation patients had bilaterally abnormal PVEPs and PERGs. In CACD the PVEP and PERG proved to be the most sensitive electrophysiological tests of preclincial macular dysfunction, 3/3 subjects abnormal. ERG recording to ISCEV guidelines were very useful in these cases; 7/8 subjects abnormal. The EOG was less useful; 4/8 subjects abnormal. CACD produces a widespread photoreceptor dysfunction in its later stages.

Correctable visual impairment in stroke rehabilitation patients

BACKGROUND

after stroke, visual impairment may exacerbate the impact of other impairments on overall disability and negatively influence rehabilitation.

OBJECTIVE

to examine the visual status of patients after stroke and determine whether this can be improved by simple interventions.

DESIGN

prospective study.

SETTINGS

stroke rehabilitation unit in a Belfast teaching hospital.

SUBJECTS

77 consecutive patients admitted for rehabilitation after acute stroke.

METHODS

full optometric and ophthalmic assessment within 2 weeks of admission.

RESULTS

of 70 patients with glasses, 19 did not have their glasses in hospital before prompting and 18 had glasses in unacceptable condition. Twenty patients had impaired visual acuity (6/12 or worse) with existing glasses (if helpful); 11 of these improved to better than 6/12 with refractive correction.

CONCLUSIONS

stroke professionals need to enquire about patients' spectacles and assess their condition. Patients with reduced visual acuity in the absence of significant non-refractive disease should be referred to an optometrist: in this series 14% of patients had visual impairment which benefited from refractive correction.

Allelic variation in the VMD2 gene in best disease and age-related macular degeneration

PURPOSE

To assess the allelic variation of the VMD2 gene in patients with Best disease and age-related macular degeneration (AMD).

METHODS

Three hundred twenty-one AMD patients, 192 ethnically similar control subjects, 39 unrelated probands with familial Best disease, and 57 unrelated probands with the ophthalmoscopic findings of Best disease but no family history were screened for sequence variations in the VMD2 gene by single-strand conformation polymorphism (SSCP) analysis. Amplimers showing a bandshift were reamplified and sequenced bidirectionally. In addition, the coding regions of the VMD2 gene were completely sequenced in six probands with familial Best disease who showed no SSCP shift.

RESULTS

Forty different probable or possible disease-causing mutations were found in one or more Best disease or AMD patients. Twenty-nine of these variations are novel. Of the 39 probands with familial Best disease, mutations were detected in all 39 (33 by SSCP and 6 by DNA sequencing). SSCP screening of the 57 probands with a clinical diagnosis of Best disease but no family history revealed 16 with mutations. Mutations were found in 5 of 321 AMD patients (1.5%), a fraction that was not significantly greater than in control individuals (0/192, 0%).

CONCLUSIONS

Patients with the clinical diagnosis of Best disease are significantly more likely to have a mutation in the VMD2 gene if they also have a positive family history. These findings suggest that a small fraction of patients with the clinical diagnosis of AMD may actually have a late-onset variant of Best disease, whereas at the same time, a considerable fraction of isolated patients with the ophthalmoscopic features of Best disease are probably affected with some other macular disease.