Macular Degeneration: Weber BH

Scholl HP, Fleckenstein M, Charbel Issa P, Keilhauer C, Holz FG, Weber BH. · Department of Ophthalmology, University of Bonn, Bonn, Germany. <> · Mol Vis. · Pubmed #17327825 links to  free full text

Abstract: Age-related macular degeneration (AMD) is a genetically complex disorder of the photoreceptor-RPE-Bruch's membrane-choriocapillaris complex. Family and twin studies have shown that the susceptibility for this disease is genetically influenced. The heritability has been estimated to be up to 71%. Linkage and association studies have identified several chromosomal regions that are likely to contain susceptibility loci with strongest evidence found on chromosome 1q31 and 10q26. Variants in the complement factor H (CFH) gene have been shown by several independent studies to be associated with an increased risk for AMD in Caucasian populations. These findings imply that the innate immune system may play a significant role in AMD pathogenesis. The LOC387715/HTRA1 locus within 10q26 has been identified as a second major locus contributing to AMD pathogenesis. The two late forms of AMD, choroidal neovascularization and geographic atrophy, have not been found to be different in risk allele distribution. Variants within CFH and LOC387715/HTRA1 may contribute to the increased risk of late AMD largely through their impact on precursors, such as drusen and/or other RPE/Bruch's membrane changes. Considering variants at CFH, LOC387715/HTRA1 and complement component 2-complement factor B (C2-FB), high-risk homozygotes at all three loci may have a 250-fold increased risk compared to baseline. However, the identification of genetic factors has not resulted in therapeutic strategies to modify the disease so far and additional genetic and environmental factors are yet to be discovered in order to influence the onset and the progression of AMD.

Scholl HP, Weber BH, Nöthen MM, Wienker T, Holz FG. · Augenklinik, Universität, Bonn. · Ophthalmologe. · Pubmed #16170519 No free full text.

Abstract: Age-related macular degeneration is a complex genetic disorder. Recent data suggest that the additive genetic risk for late-stage disease is more than two-thirds. Comprehensive genetic studies (candidate gene approaches, linkage and association studies) have been performed in recent years to identity the genetic risk factors at the molecular lavel. Very recently, a significant risk allele, Y402H, has been discovered in the complement factor H (CFH) gene. The relative risk of developing AMD has been estimated between 2.4-4.6 for heterozygotes and 3.3-7.4 for homozygotes. This polymorphism accounts for approximately 20-50% of the overall risk of developing AMD. In this review the results from molecular genetic studies in AMD are summarized, with a special emphasis on the recent data obtained for the CFH gene.

Stöhr H, Milenkowic V, Weber BH. · Institut für Humangenetik, Biozentrum der Bayerischen Julius-Maximilians Universität, Würzburg. · Ophthalmologe. · Pubmed #15627199 No free full text.

Abstract: Best's vitelliform macular dystrophy (Best's disease) is an autosomal dominant disease of the central retina and is caused by mutations in the VMD2 gene located on the long arm of chromosome 11. VMD2 encodes bestrophin, a transmembrane protein with putative Ca(2+)-dependent chloride channel activity at the basolateral portion of the retinal pigment epithelium. The N-terminal half of bestrophin reveals high sequence homology to three bestrophin-like proteins in humans but also to protein sequences from evolutionarily distant organisms. Most of the known VMD2 mutations are located within this presumably important functional part of the protein and cause amino acid substitutions and small in-frame deletions of single amino acid residues. The pathogenicity of VMD2 mutations is likely based on a dominant negative effect possibly by oligomerization of normal and mutated bestrophin molecules to form a defective ion channel. Missense mutations in VMD2 were also shown to be associated with vitreoretinochoroidopathy and ocular developmental abnormalities. In this case, the pathogenic sequence changes influence the peptide sequences but simultaneously alter the regulation of mRNA splicing and maturation. Different disease mechanisms may therefore be responsible for the distinct phenotypes associated with VMD2 mutations.

White K, Marquardt A, Weber BH. · Institut für Humangenetik, Universität Würzburg, Würzburg, Germany. · Hum Mutat. · Pubmed #10737974 No free full text.

Abstract: Mutations in the gene VMD2 are associated with autosomal dominant vitelliform macular dystrophy (Best disease). VMD2 is expressed in the retinal pigment epithelium and codes for a 585 amino acid putative transmembrane protein with undetermined functional properties. To date, 48 different mutations, predominantly missense, have been described in Best disease families. These mutations generally affect amino acids in the first 50% of the protein, and occur in four distinct clusters possibly representing regions of functional importance. VMD2 has also been investigated in other macular diseases. Mutations have been documented in a significant percentage of patients with adult vitelliform macular dystrophy (AVMD) and in a single case of "bull's-eye" maculopathy. Results of analysis in two large series of individuals with age-related macular degeneration (AMD) suggest that VMD2 does not play a major role in this prevalent disorder.

Zack DJ, Dean M, Molday RS, Nathans J, Redmond TM, Stone EM, Swaroop A, Valle D, Weber BH. · Departments of Ophthalmology, Molecular Biology and Genetics, and Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA. · Mol Vis. · Pubmed #10562654 links to  free full text

Abstract: Age-related macular degeneration (AMD) is increasingly recognized as a complex genetic disorder in which one or more genes contribute to an individual's susceptibility for developing the condition. Twin and family studies as well as population-based genetic epidemiologic methods have convincingly demonstrated the importance of genetics in AMD, though the extent of heritability, the number of genes involved, and the phenotypic and genetic heterogeneity of the condition remain unresolved. The extent to which other hereditary macular dystrophies such as Stargardts disease, familial radial drusen (malattia leventinese), Best's disease, and peripherin/RDS-related dystrophy are related to AMD remains unclear. Alzheimer's disease, another late onset, heterogeneous degenerative disorder of the central nervous system, offers a valuable model for identifying the issues that confront AMD genetics.

Fritsche LG, Freitag-Wolf S, Bettecken T, Meitinger T, Keilhauer CN, Krawczak M, Weber BH. · Institute of Human Genetics, University of Regensburg, Regensburg, Germany. · Hum Mutat. · Pubmed #19384966 No free full text.

Abstract: Age-related macular degeneration (AMD) is a frequent, multifactorial disease of the central retina and a major cause of irreversible vision loss in industrialized countries. Apolipoprotein E (APOE) has been consistently associated with AMD, particularly its two functional isoforms E2 (predisposing) and E4 (protective). The biological correlate of this association, however, is still unclear. In this study, we have defined an extended haplotype block encompassing the entire APOE gene locus, including known coding as well as cis-regulatory promoter variants. Of the five extended APOE haplotypes common in the general population, two were found to be significantly associated with AMD, namely G-G-G-G-epsilon2 (odds ratio [OR], 1.59; 95% confidence interval [CI], 1.19-2.12) and T-G-A-G-epsilon4 (OR, 0.76; 95% CI, 0.58-0.99). When analyzing common extended haplotype combinations, T-C-G-G-epsilon3/T-G-A-G-epsilon4 exhibited the most prominent effect (OR, 0.32; 95% CI, 0.20-0.51). Intriguingly, we also found one extended epsilon3-haplotype, G-G-G-A-epsilon3, to be protective in the homozygous state (OR, 0.65; 95% CI, 0.49-0.87). Since single nucleotide polymorphism (SNP) rs405509:G>T is a constituent of the extended epsilon-haplotype block and is known to significantly influence APOE promoter activity, we hypothesize that both the relative rate of APOE isoform expression in conjunction with established functional differences of the respective isoforms may be crucial in mediating AMD pathology. This would also imply that genotyping of the core epsilon-haplotypes alone is not sufficient to estimate AMD risk, but that determination of extended haplotype combinations, including the functional promoter SNP rs405509, is required instead.

Renner AB, Fiebig BS, Weber BH, Wissinger B, Andreasson S, Gal A, Cropp E, Kohl S, Kellner U. · Augenklinik, Charité-Universitätsmedizin Berlin, Germany. · Am J Ophthalmol. · Pubmed #19038374 No free full text.

Abstract: PURPOSE: To describe the phenotypic variability in 22 patients with PRPH2 gene mutations and to report six novel mutations. DESIGN: Retrospective study. METHODS: Clinical examinations included color vision testing, perimetry, fundus autofluorescence (FAF), fluorescein angiography, optical coherence tomography (OCT), and full-field and multifocal electroretinography (International Society for Clinical Electrophysiology of Vision standards). Blood samples were taken for deoxyribonucleic acid (DNA) extraction and mutation screening was performed by direct sequencing of polymerase chain reaction amplicons. RESULTS: Eleven unrelated patients and four unrelated families each with two affected members as well as one family with three affected members were examined. Diagnoses included central areolar choroidal dystrophy (CACD; n = 9), autosomal dominant retinitis pigmentosa (adRP; n = 7), adult vitelliform macular dystrophy (n = 3), and cone-rod dystrophy (CRD; n = 3). FAF was abnormal in all patients and showed various retinal pigment epithelial alterations, in CACD with a speckled FAF pattern. OCT revealed reduced retinal thickness, mostly in CACD, subretinal lesions, macula edema, or was normal. Follow-up (n = 12; range, 1.3 to 26 years) showed a slow progression of the retinal dystrophies. DNA testing revealed previously reported PRPH2 mutations in two families and eight individuals of whom two carried the same mutation but had different phenotypes. Novel PRPH2 mutations were detected in two families with adRP, in identical twins with CACD, and in each of an individual with CACD, CRD, and adRP. CONCLUSIONS: This series describes the broad spectrum of phenotypes associated with PRPH2 mutations. FAF and OCT are helpful tools for diagnosis and evaluation of disease progression. We report novel PRPH2 mutations in patients with CACD, CRD, and adRP.

Scholl HP, Charbel Issa P, Walier M, Janzer S, Pollok-Kopp B, Börncke F, Fritsche LG, Chong NV, Fimmers R, Wienker T, Holz FG, Weber BH, Oppermann M. · Department of Ophthalmology, University of Bonn, Bonn, Germany. · PLoS One. · Pubmed #18596911 links to  free full text

Abstract: Dysregulation of the alternative pathway (AP) of complement cascade has been implicated in the pathogenesis of age-related macular degeneration (AMD), the leading cause of blindness in the elderly. To further test the hypothesis that defective control of complement activation underlies AMD, parameters of complement activation in blood plasma were determined together with disease-associated genetic markers in AMD patients. Plasma concentrations of activation products C3d, Ba, C3a, C5a, SC5b-9, substrate proteins C3, C4, factor B and regulators factor H and factor D were quantified in patients (n = 112) and controls (n = 67). Subjects were analyzed for single nucleotide polymorphisms in factor H (CFH), factor B-C2 (BF-C2) and complement C3 (C3) genes which were previously found to be associated with AMD. All activation products, especially markers of chronic complement activation Ba and C3d (p<0.001), were significantly elevated in AMD patients compared to controls. Similar alterations were observed in factor D, but not in C3, C4 or factor H. Logistic regression analysis revealed better discriminative accuracy of a model that is based only on complement activation markers Ba, C3d and factor D compared to a model based on genetic markers of the complement system within our study population. In both the controls' and AMD patients' group, the protein markers of complement activation were correlated with CFH haplotypes.This study is the first to show systemic complement activation in AMD patients. This suggests that AMD is a systemic disease with local disease manifestation at the ageing macula. Furthermore, the data provide evidence for an association of systemic activation of the alternative complement pathway with genetic variants of CFH that were previously linked to AMD susceptibility.

Fritsche LG, Loenhardt T, Janssen A, Fisher SA, Rivera A, Keilhauer CN, Weber BH. · Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany. · Nat Genet. · Pubmed #18511946 No free full text.

Abstract: Age-related macular degeneration (AMD) is a prevalent multifactorial disorder of the central retina. Genetic variants at two chromosomal loci, 1q31 and 10q26, confer major disease risks, together accounting for more than 50% of AMD pathology. Signals at 10q26 center over two nearby genes, ARMS2 (age-related maculopathy susceptibility 2, also known as LOC387715) and HTRA1 (high-temperature requirement factor A1), suggesting two equally probable candidates. Here we show that a deletion-insertion polymorphism in ARMS2 (NM_001099667.1:c.(*)372_815del443ins54) is strongly associated with AMD, directly affecting the transcript by removing the polyadenylation signal and inserting a 54-bp element known to mediate rapid mRNA turnover. As a consequence, expression of ARMS2 in homozygous carriers of the indel variant is not detectable. Confirming previous findings, we demonstrate a mitochondrial association of the normal protein and further define its retinal localization to the ellipsoid region of the photoreceptors. Our data suggest that ARMS2 has a key role in AMD, possibly through mitochondria-related pathways.

Fogarasi M, Janssen A, Weber BH, Stöhr H. · Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, D-93053 Regensburg, Germany. · Matrix Biol. · Pubmed #18295466 No free full text.

Abstract: Sorsby fundus dystrophy (SFD) is an autosomal dominant macular degeneration of late onset. A key feature of the disease is the thickening of Bruch's membrane, an ECM structure located between the RPE and the choroid. SFD is caused by mutations in the gene encoding the ECM-associated tissue inhibitor of metalloproteases-3 (TIMP3). We have recently generated two Timp3 gene-targeted mouse lines, one deficient for the murine gene (Timp3-/-) and one carrying an SFD-related S156C mutation. Based on extracts and cell cultures derived from tissues of these animals we now evaluated TIMP3 functionality and its contribution to SFD. We show that the activity levels of TIMP3 target proteases including TACE, ADAMTS4/5 and aggrecan-cleaving MMPs are similar in Timp3S156/+ and Timp3S156C/S156C mice when compared to controls. In Timp3-/- mice, a significant enhancement of enzyme activity was observed for TACE but not for ADAMTS4/5 and MMPs indicating a compensatory effect of other inhibitors regulating the latter two groups of proteases. Fibrin bead assays show that angiogenesis in Timp3S156/+ and Timp3S156C/S156C mice is not altered whereas increased formation of capillary tubes was observed in Timp3-/- animals over controls. Rescue experiments using recombinant proteins demonstrate that the inhibitory activities of TIMP3 towards TACE and aggrecan-cleaving MMPs as well as the anti-angiogenic properties of TIMP3 are not impaired by SFD mutation S156C. We finally demonstrate that wild-type and S156C-TIMP3 proteins block the binding of VEGF to its receptor VEGFR2 to a similar extent. Taken together, this study shows that S156C-TIMP3 retains its known functional properties suggesting that causes other than an imbalance in protease or angiogenic activities represent the primary molecular defect underlying SFD.

Skerka C, Lauer N, Weinberger AA, Keilhauer CN, Sühnel J, Smith R, Schlötzer-Schrehardt U, Fritsche L, Heinen S, Hartmann A, Weber BH, Zipfel PF. · Department of Infection Biology, Leibniz Institute for Natural Products Research and Infection Biology, Hans Knöll Institute, Jena, Germany. · Mol Immunol. · Pubmed #17399790 No free full text.

Abstract: The common variant in the human complement Factor H gene (CFH), with Tyr402His, is linked to age-related macular degeneration (AMD), a prevalent disorder leading to visual impairment and irreversible blindness in elderly patients. Here we show that the risk variant CFH 402His displays reduced binding to C reactive protein (CRP), heparin and retinal pigment epithelial cells. This reduced binding can cause inefficient complement regulation at the cell surface, particularly when CRP is recruited to injured sites and tissue. In addition, we identify the Factor H-like protein 1 (FHL-1), an alternative splice product of the CFH gene as an additional protein that includes the risk residue 402, and thus confers risk for AMD. FHL-1 is expressed in the eye and the FHL-1 402His risk variant shows similar reduced cell binding and likely reduced complement regulatory functions on the cell surface. CFH and FHL-1 may act in concert in the eye and the reduced surface binding may result in inappropriate local complement control, which in turn can lead to inflammation, disturbance of local physiological homeostasis and progression to cell damage. As a consequence, these processes may lead to AMD pathogenesis.

Fisher SA, Rivera A, Fritsche LG, Keilhauer CN, Lichtner P, Meitinger T, Rudolph G, Weber BH. · Department of Medical and Molecular Genetics, Guy's King's and St Thomas' School of Medicine, King's College London, London, United Kingdom. · Hum Mutat. · Pubmed #17216616 No free full text.

Abstract: This article reports a well-powered age-related macular degeneration (AMD) case-control association study in the HMCN1 gene, showing that common variants do not account for a substantial proportion of AMD cases. Thus, the consistent linkage peak observed by several genome-wide linkage scans within the 1q32 region is unlikely to be attributed to polymorphisms at the HMCN1 locus. In addition, the analysis provides comprehensive data suggesting that low-frequency variants encoding possible functional amino acid polymorphisms in the HMCN1 gene may not contribute substantially to disease, although HMCN1 mutations may still confer disease susceptibility in a small subset of patients. Interestingly, the HMCN1 p.Gln5346Arg mutation, which is thought to be a causal mutation in a large AMD pedigree segregating the disease as a single-gene trait, appears to occur in our control cohort as a low-frequency polymorphism with an allele frequency of approximately 0.0026.

Fisher SA, Rivera A, Fritsche LG, Babadjanova G, Petrov S, Weber BH. · Department of Medical and Molecular Genetics, Guy's King's and St Thomas' School of Medicine, King's College, London, UK. · Br J Ophthalmol. · Pubmed #17050575 No free full text.

Abstract: BACKGROUND/AIMS: A strong association has been confirmed between age-related macular degeneration (AMD) and variants at two independent loci including Tyr402His in the complement factor H (CFH) on 1q32 and Ser69Ala at LOC387715, a hypothetical gene on chromosome 10q26. The contribution of both loci to AMD was investigated in an isolated north-west Russian population. METHODS: Together with a PLEKHA1 variant at 10q26, the CFH Tyr402His and LOC387715 Ser69Ala polymorphisms were genotyped in 155 patients with AMD and 151 age-matched controls. chi(2) and Mantel-Haenszel (M-H) score tests were used to test for association. Sex-adjusted ORs were calculated. RESULTS: The frequency of the Tyr402His C allele was significantly higher in patients with AMD compared with controls (p(M-H)=0.0035). The increased risk observed in patients homozygous for the C allele (OR(HOM)=2.71, 95% CI 1.25 to 5.90) in this indigenous Russian population was considerably lower than that observed in previous western Caucasian populations. A significant increase in the frequency of the LOC387715 variant was observed in patients with late-stage AMD compared with controls (p(M-H)=0.007), with a homozygous OR of 3.47 (95% CI 1.01 to 11.9), although this association was not seen with early-stage AMD. CONCLUSION: The CFH gene contributes to AMD in this Russian population, although the risk conferred is considerably lower in this population than that found in other Western populations. A contribution of LOC387715 to disease in this population is also likely to be of weak effect.

Rivera A, Fisher SA, Fritsche LG, Keilhauer CN, Lichtner P, Meitinger T, Weber BH. · Institute of Human Genetics, University of Regensburg, Germany. · Hum Mol Genet. · Pubmed #16174643 links to  free full text

Abstract: Age-related macular degeneration (AMD) is a multifactorial disease and a prevalent cause of visual impairment in developed countries. Risk factors include environmental components and genetic determinants. The complement factor H (CFH) has been the first major susceptibility gene for AMD identified within 1q32. Here, we focused on a second region of interest in 10q26 where a recent meta-analysis revealed strongest evidence for linkage to AMD at a genome-wide significance level. Within an interval of 22 Mb, we have analyzed 93 single nucleotide polymorphisms for allelic association with AMD in two independent case-control cohorts of German origin (AMD(combined) n=1166; controls(combined) n=945). Significant association was found across a 60 kb region of high linkage disequilibrium harboring two genes PLEKHA1 and hypothetical LOC387715. The strongest association (P=10(-34)) centered over a frequent coding polymorphism, Ala69Ser, at LOC387715, strongly implicating this gene in the pathogenesis of AMD. Besides abundant expression in placenta, we demonstrate weak expression of LOC387715 in the human retina. At present, however, there is no functional information on this gene, which appears to have evolved recently within the primate lineage. The joint contribution of the common risk allele at LOC387715, Ala69Ser, and at CFH, Tyr402His, was assessed in our case-control population, which suggests an additive model indicating an independent contribution of the two gene loci to disease risk. Our data show a disease odds ratio of 57.6 (95% CI: 37.2, 89.0) conferred by homozygosity for risk alleles at both CFH and LOC387715 when compared with the baseline non-risk genotype.

Min SH, Molday LL, Seeliger MW, Dinculescu A, Timmers AM, Janssen A, Tonagel F, Tanimoto N, Weber BH, Molday RS, Hauswirth WW. · Department of Ophthalmology, University of Florida College of Medicine, Gainesville, 32610, USA. · Mol Ther. · Pubmed #16027044 No free full text.

Abstract: X-linked juvenile retinoschisis (RS) is a common cause of juvenile macular degeneration in males. RS is characterized by cystic spoke-wheel-like maculopathy, peripheral schisis, and a negative (b-wave more reduced than a-wave) electroretinogram (ERG). These symptoms are due to mutations in the RS1 gene in Xp22.2 leading to loss of functional protein. No medical treatment is currently available. We show here that in an Rs1h-deficient mouse model of human RS, delivery of the human RS1 cDNA with an AAV vector restored expression of retinoschisin to both photoreceptors and the inner retina essentially identical to that seen in wild-type mice. More importantly, unlike an earlier study with a different AAV vector and promoter, this work shows for the first time that therapeutic gene delivery using a highly specific AAV5-opsin promoter vector leads to progressive and significant improvement in both retinal function (ERG) and morphology, with preservation of photoreceptor cells that, without treatment, progressively degenerate.

Fisher SA, Abecasis GR, Yashar BM, Zareparsi S, Swaroop A, Iyengar SK, Klein BE, Klein R, Lee KE, Majewski J, Schultz DW, Klein ML, Seddon JM, Santangelo SL, Weeks DE, Conley YP, Mah TS, Schmidt S, Haines JL, Pericak-Vance MA, Gorin MB, Schulz HL, Pardi F, Lewis CM, Weber BH. · Department of Medical and Molecular Genetics, Guy's, King's and St Thomas' School of Medicine, King's College London, London SE1 9RT, UK. · Hum Mol Genet. · Pubmed #15987700 links to  free full text

Abstract: A genetic contribution to the development of age-related macular degeneration (AMD) is well established. Several genome-wide linkage studies have identified a number of putative susceptibility loci for AMD but only a few of these regions have been replicated in independent studies. Here, we perform a meta-analysis of six AMD genome screens using the genome-scan meta-analysis method, which allows linkage results from several studies to be combined, providing greater power to identify regions that show only weak evidence for linkage in individual studies. Results from non-parametric analysis for a broad AMD clinical phenotype (including two studies with quantitative traits) were extracted. For each study, 120 genomic bins of approximately 30 cM were defined and ranked according to maximum evidence for linkage within each bin. Bin ranks were weighted according to study size and summed across all studies; the summed rank (SR) for each bin was assessed empirically for significance using permutation methods. A high SR indicates a region with consistent evidence for linkage across studies. The strongest evidence for an AMD susceptibility locus was found on chromosome 10q26 where genome-wide significant linkage was observed (P=0.00025). Several other regions met the empirical significance criteria for bins likely to contain linked loci including adjacent pairs of bins on chromosomes 1q, 2p, 3p and 16. Several of the regions identified here showed only weak evidence for linkage in the individual studies. These results will help prioritize regions for future positional and functional candidate gene studies in AMD.

Renner AB, Tillack H, Kraus H, Krämer F, Mohr N, Weber BH, Foerster MH, Kellner U. · Augenklinik, Charité Campus Benjamin Franklin, Universitätsmedizin Berlin, Berlin, Germany. · Ophthalmology. · Pubmed #15808248 No free full text.

Abstract: PURPOSE: To perform a detailed morphologic and functional evaluation of Best macular dystrophy (BMD) associated with mutations in the VMD2 gene. DESIGN: Retrospective study. PARTICIPANTS: The records of 16 patients with BMD and heterozygous VMD2 mutations (group 1) and 5 patients with Best-like lesions with no detectable disease-associated alterations in the VMD2 gene (group 2) were evaluated retrospectively. METHODS: The data were reviewed regarding visual acuity (VA), color vision, perimetry, autofluorescence of the retinal pigment epithelium (RPE), fluorescein angiography, electro-oculography (EOG), and full-field electroretinography (ERG) and multifocal ERG (mfERG). MAIN OUTCOME MEASURES: VMD2 mutations, age at onset of BMD, RPE autofluorescence, EOG, ERG, and mfERG. RESULTS: The mean age of the patients in group 1 was 47.1 years (range, 16.7-86.5), and age at onset varied between 5 and 58 years (median, 42.0). Visual acuity ranged between 20/16 and 20/400 (median, 20/40). No association existed between the specific nature of the VMD2 mutation and disease onset or expressivity. Retinal pigment epithelium autofluorescence was increased corresponding to ophthalmoscopically visible yellow material, whereas it was decreased in the atrophic stage of BMD. Electro-oculography light rise was reduced in 18 of 19 eyes. Electroretinography amplitudes were normal in 3 patients and reduced in 6 patients. Multifocal ERG revealed in 10 of 20 eyes a central amplitude reduction and in 7 eyes a generalized one. There were no marked differences in clinical and functional findings between the patients in groups 1 and 2, except that the mean age of the patients in group 2 was higher (64.0 years [range, 45.7-80.6]) and the median VA lower (20/50 [range, 20/32-20/320]). CONCLUSIONS: The onset of BMD is highly variable and occurred in the majority of patients after the second decade of life. Best-like lesions may develop in older patients without associated VMD2 mutations. Those manifestations may be related to a specific form of age-related macular degeneration. This article contains additional online-only material available at .

Renner AB, Tillack H, Kraus H, Kohl S, Wissinger B, Mohr N, Weber BH, Kellner U, Foerster MH. · Augenklinik, Campus Benjamin Franklin, Charité Universitätsmedizin Berlin, Berlin, Germany. · Retina. · Pubmed #15579992 No free full text.

Abstract: PURPOSE: Detailed morphologic and functional evaluation of adult vitelliform macular dystrophy (AVMD). METHODS: The records of 61 consecutive AVMD patients (inclusion criterion: vitelliform lesion smaller than one disk diameter at least in one eye) were evaluated retrospectively regarding visual acuity, color vision, perimetry, retinal pigment epithelium (RPE) autofluorescence, fluorescein angiography, electro-oculography, full-field and multifocal electroretinography, and molecular genetic evaluation of the VMD2 and RDS/peripherin genes. RESULTS: The mean age of subjects was 54.6 years. Visual loss was variable (median, 0.6; range, 1.25-0.05). Color vision and visual field were normal in about half of the patients but presented defects with high variability in the remaining patients. Autofluorescence findings showed increased fluorescence within the foveal yellow lesion in 76%. In the majority of eyes, the amplitude of the 30 Hz flicker response of the full-field electroretinogram (72%) and the central P1 amplitude of the multifocal electroretinogram (63%) were reduced. Mutational analyses revealed a potentially disease-associated mutation in the RDS/peripherin gene in one patient. CONCLUSION: AVMD is characterized by late onset, slow progression, good prognosis, and high variability of morphologic and functional abnormalities resulting frequently in misdiagnosis. Autofluorescence findings indicate lipofuscin accumulation in the yellow lesion. Electroretinography revealed a generalized cone system dysfunction with increasing severity toward the fovea.

Krämer F, Mohr N, Kellner U, Rudolph G, Weber BH. · Institut für Humangenetik, Universität Würzburg, D-97072 Würzburg, Germany. · Hum Mutat. · Pubmed #14517959 No free full text.

Abstract: Mutations in the vitelliform macular dystrophy 2 (VMD2) gene encoding besrtophin are responsible for Best macular dystrophy (BMD), a juvenile-onset autosomal dominant disorder of the central retina. Here, we report ten novel VMD2 mutations identified in clinically diagnosed BMD patients. The heterozygous alterations include nine missense mutations (c.32A>T, c.76G>C, c.85T>C, c.122T>C, c.122T>C, c.310G>C, c.722C>A, c.880C>G, c.893T>C) resulting in amino acid changes (respectively: Asn11Ile, Gly26Arg, Tyr29His, Leu41Pro, Trp102Arg, Asp104His, Thr241Asn, Leu294Val and Phe298Ser) located within four previously defined hotspot regions of the gene. In addition, a silent exonic mutation (c.624G>A) was identified in a two generation BMD pedigree. To determine a possible pathogenic effect of this variant, the consequences on splicing behaviour and potential exonic splice enhancer (ESE) motifs were analyzed. Finally, a 1-bp deletion (c.779delC) resulting in a frameshift mutation (Pro260fsX288) was found in exon 7, representing the first case of a potential frameshift mutation that affects the N-terminal half of the VMD2 protein. Besides a dominant negative effect which is likely attributable to the identified missense mutations, the deletion mutation suggests haploinsufficiency as an infrequent disease-causing mechanism in BMD.

Soboleva G, Geis B, Schrewe H, Weber BH. · Institut für Humangenetik, Biozentrum, Julius-Maximilians-Universität Würzburg, Würzburg, Germany. · J Cell Physiol. · Pubmed #12942551 No free full text.

Abstract: The tissue inhibitor of metalloproteinases-3 (TIMP3) is a multifunctional protein tightly associated with the extracellular matrix (ECM). A specific type of mutation in TIMP3 which results in potentially unpaired cysteine residues at the C-terminus of the protein has been shown to cause Sorsby fundus dystrophy (SFD), an autosomal dominant retinopathy of late onset. An early finding in SFD is a striking accumulation of protein and lipid material in Bruch's membrane, a multilayered ECM structure located between the choroid and the RPE. To study the molecular mechanisms underlying SFD pathology, we recently generated two mouse lines, one deficient in Timp3 (Timp3(-/-)) and one carrying an SFD-related mutation in the orthologous murine Timp3 gene (Timp3(S156C/S156C)). We now established immortalized fibroblast cells from the mutant mouse strains and provide evidence that the various cell lines display distinct morphological and physiological features that are dependent on the mutational status of the Timp3 protein in the secreted ECM. We show that matrix metalloproteinase (MMP) activity and inhibitory properties of Timp3 are not affected by the SFD-associated mutation. We further demonstrate that Timp3(S156C) protein accumulates in the ECM of the mutant fibroblast cells and that this accumulation is not due to a prolonged turnover rate of mutant vs. normal Timp3. We also show that the relative abundance of mutant and normal Timp3 in the ECM has no measurable effects on cellular phenotypes. Together, these findings suggest (i) a functional role of normal Timp3 in pathways determining cellular morphology and (ii) a loss of this particular function as a consequence of the Ser156Cys mutation. We therefore hypothesize that SFD pathogenesis is due to a loss-of-function mutation in TIMP3.

Gerth C, Andrassi-Darida M, Bock M, Preising MN, Weber BH, Lorenz B. · Department of Paediatric Opthalmology, Strabismology and Opthalmogenetics, Klinikum, University of Regensburg, Germany. · Graefes Arch Clin Exp Ophthalmol. · Pubmed #12192456 No free full text.

Abstract: PURPOSE: To determine the phenotypic variability in patients with compound heterozygous or homozygous ABCA4 mutations, and to correlate the phenotypes with the functional properties of the altered protein. METHODS: Sixteen patients from 13 families with signs of Stargardt macular dystrophy/fundus flavimaculatus and known mutations on both alleles of the ABCA4 gene (15 compound heterozygous, one homozygous) were characterized by clinical examination, fundus autofluorescence, psychophysics (color vision, kinetic and two-color dark- and light-adapted static threshold perimetry), and electrophysiology (Ganzfeld, multifocal ERG, EOG). RESULTS: The homozygous 5917delG mutation resulted in the earliest disease manifestation (at 5 years) and a general cone-rod dysfunction, whereas the compound heterozygous mother (5917delG, G1961E) exhibited a very mild phenotype. Compound heterozygotes for the IVS40+5G-->A and the C1488Y or Y362X mutation showed also an early age of onset but only a central dysfunction. The effect of the 2588G-->C mutation, the G1961E mutation, and the complex mutation L541P-A1038V depended on the mutation in the second allele. Genotype-phenotype correlation appeared possible in most instances. Psychophysics revealed a simultaneous yet not necessarily congruent cone and rod dysfunction. CONCLUSIONS: The type and combination of ABCA4 mutations in compound heterozygous patients determined were compatible with the severity of the phenotype as to age of onset and the functional consequences in the majority of patients. Unexplained phenotypic differences indicate the influence of other factors. ABCA4 mutations result in cone and rod dysfunction. Different disease durations limit the power of presently available genotype-phenotype correlations.

Frisch IB, Haag P, Steffen H, Weber BH, Holz FG. · Department of Ophthalmology, University of Heidelberg, Germany. · Ophthalmology. · Pubmed #12153800 No free full text.

Abstract: OBJECTIVE: Syndromes with genetically determined retinal diseases and concurrent multiple neurologic abnormalities are rare. Kjellin described an autosomal recessive entity with spastic paraplegia, mental retardation, amyotrophia, and macular dystrophy. We sought to further characterize the retinal phenotype and to contrast fundus changes and the genotype to Stargardt's disease in a young patient with progressive Kjellin's syndrome. DESIGN: Observational case report and family genetic study. PATIENTS: One affected and 11 unaffected members of a family with Kjellin's syndrome were investigated. METHODS: Complete ophthalmologic and neurologic examinations were performed, including electrophysiologic evaluation, color vision assessment, fundus autofluorescence, and fluorescence angiography. To investigate a possible role of the ABCA4 gene in the etiology of the macular changes, the entire 50 coding exons, including flanking intronic sequences of the patient, were analyzed by direct sequencing. MAIN OUTCOME MEASURES: The patient was evaluated for her symptoms, retinal function, fundus autofluorescence, angiography, and mutations in the ABCA4 gene. RESULTS: A 27-year-old female patient initially was seen with trembling of her right hand. Subsequently, progressive paraspasticity occurred, and a diagnostic workup revealed mild mental retardation. Biomicroscopy disclosed symmetric multiple round yellowish flecks at the level of the retinal pigment epithelium scattered at the posterior pole, which showed increased intrinsic fluorescence in the center, with a halo of reduced autofluorescence. Multifocal electroretinography elicited abnormal responses in the macular area in the presence of normal Ganzfeld electroretinography recordings. In gene mapping, several common variants were identified, although none seem to be associated with the disease features. CONCLUSIONS: Macular changes in Kjellin's syndrome share phenotypic characteristics with Stargardt's disease, although there are differences with regard to appearance, distribution, angiographic, and autofluorescence behavior of the retinal flecks. Ophthalmologic examination is prudent in patients with similar neurologic deficits, because it is essential for the diagnosis and because visual symptoms may be absent even in the presence of obvious and widespread retinal manifestations. The abnormal gene product in Kjellin's syndrome seems to cause progressive dysfunction in various neuronal tissues but seems to be distinct from the major defect underlying the Stargardt's disease phenotype.

Weber BH, Lin B, White K, Kohler K, Soboleva G, Herterich S, Seeliger MW, Jaissle GB, Grimm C, Reme C, Wenzel A, Asan E, Schrewe H. · Institute of Human Genetics, Biocenter, University of Wuerzburg, Germany. · Invest Ophthalmol Vis Sci. · Pubmed #12147610 links to  free full text

Abstract: PURPOSE: Sorsby fundus dystrophy (SFD) is a rare, late-onset macular dystrophy caused by mutations in the tissue inhibitor of metalloproteinases-3 (TIMP3) gene. The known mutations introduce potentially unpaired cysteine residues in the C terminus of the protein and result in the formation of higher-molecular-weight protein complexes of as yet unknown composition and functional consequences in the pathologic course of SFD. To facilitate in vivo investigation of mutant TIMP3, the authors generated a knock-in mouse carrying a disease-related Ser156Cys mutation in the orthologous murine Timp3 gene. METHODS: Site-directed mutagenesis and homologous recombination in embryonic stem (ES) cells was used to generate mutant ES cells carrying the Timp3(S156C) allele. Chimeric animals were obtained, of which two displayed germline transmission of the mutated allele. Molecular genetic, biochemical, electron microscopic, and electrodiagnostic techniques were used for characterization. RESULTS: At 8 months of age, knock-in mice showed abnormalities in the inner aspect of Bruch's membrane and in the organization of the adjacent basal microvilli of the retinal pigment epithelium (RPE). Changes resembling those in the mutant animals were also present to some extent in normal littermates, but only at an advanced age of 30 months. Long-term electrodiagnostic recordings indicated normal retinal function throughout life. The biochemical characteristics of the mutant protein appear similar in humans and knock-in mice, suggesting common molecular pathways in the two species. The localization of the mutant protein in the eye is normal, although there is evidence of increased Timp3 levels in Bruch's membrane of mutant animals. CONCLUSIONS: The knock-in mice display early features of age-related changes in Bruch's membrane and the RPE that may represent the primary clinical manifestations of SFD. In addition, our immunolabeling studies and biochemical data support a model proposing that site-specific excess rather than absence or deficiency of functional Timp3 may be the primary consequence of the known Timp3 mutations.

Stöhr H, Marquardt A, Nanda I, Schmid M, Weber BH. · Institut für Humangenetik, Universität Würzburg, Germany. · Eur J Hum Genet. · Pubmed #12032738 links to  free full text

Abstract: The RFP-TM protein family was first described in Caenorhabditis elegans as hypothetical transmembrane proteins containing a conserved 350-400 amino acid domain including the invariant peptide motif RFP. The VMD2 gene underlying Best disease was shown to represent the first human member of the RFP-TM protein family. More than 97% of the disease-causing mutations are located in the N-terminal RFP-TM domain implying important functional properties. Here, we have identified three novel VMD2-related human genes (VMD2L1, VMD2L2 and VMD2L3) demonstrating a high degree of conservation in their respective RFP-TM domains. Each of the VMD2-like proteins has a unique C-terminus that lack similarity to other proteins or motifs. By FISH analysis, VMD2L1 was localised to chromosome 19p13.2-p13.12, VMD2L2 to 1p32.3-p33 and VMD2L3 to 12q14.2-q15. RT-PCR analyses revealed tissue-restricted expression of the three genes with both VMD2L1 and VMD2L2 abundantly transcribed in colon. VMD2L1 is present in the retinal pigment epithelium while VMD2L3 shows predominant expression in skeletal muscle.

Weber BH, Schrewe H, Molday LL, Gehrig A, White KL, Seeliger MW, Jaissle GB, Friedburg C, Tamm E, Molday RS. · Institute of Human Genetics, Biocenter, University of Würzburg, D-97074 Würzburg, Germany. · Proc Natl Acad Sci U S A. · Pubmed #11983912 links to  free full text

Abstract: Deleterious mutations in RS1 encoding retinoschisin are associated with X-linked juvenile retinoschisis (RS), a common form of macular degeneration in males. The disorder is characterized by a negative electroretinogram pattern and by a splitting of the inner retina. To gain further insight into the function of the retinoschisin protein and its role in the cellular pathology of RS, we have generated knockout mice deficient in Rs1h, the murine ortholog of the human RS1 gene. We show that pathologic changes in hemizygous Rs1h(-/Y) male mice are evenly distributed across the retina, apparently contrasting with the macula-dominated features in human. Similar functional anomalies in human and Rs1h(-/Y) mice, however, suggest that both conditions are a disease of the entire retina affecting the organization of the retinal cell layers as well as structural properties of the retinal synapse.