Macular Degeneration: Weleber RG

Schultz DW, Weleber RG, Lawrence G, Barral S, Majewski J, Acott TS, Klein ML. · Macular Degeneration Center, Casey Eye Institute, Oregon Health & Science University, 3375 SW Terwilliger Boulevard, Portland, OR 97239-4197, U.S.A. · Ophthalmic Genet. · Pubmed #16020313 No free full text.

Abstract: Age-related macular degeneration (AMD) is the most common blinding disorder in the Western world. Similar to other common diseases in which age is a risk factor (e.g., type II diabetes or Alzheimer's disease), AMD is thought to have a complex etiology. Previously, a Gln5345Arg mutation in HEMICENTIN-1 was found to segregate with AMD in a large family. However, the population frequency of this allele is inconsistent with the large proportion of families shown by linkage studies to map near this gene at 1q31. This review summarizes current knowledge regarding the role of HEMICENTIN-1 in AMD, the results of association studies for the Gln5345Arg mutation, and the linkage evidence for an AMD locus on 1q31. The data can be reconciled through proposing both additional variants in HEMICENTIN-1 and a second genetic risk factor for AMD in the region.

Francis PJ, Hamon SC, Ott J, Weleber RG, Klein ML. · Macular Degeneration Center, Casey Eye Institute, Oregon Health & Science University, Portland, Oregon 97239-4197, USA. · J Med Genet. · Pubmed #19015224 No free full text.

Abstract: BACKGROUND: Age related macular degeneration (AMD) is a leading cause of blindness. AMD is a complex disorder caused by genetic and environmental factors in which single nucleotide polymorphisms (SNPs) in the genes CFH and LOC387715/HTRA1/ARMS2 have prognostic importance for progression to advanced AMD (with visual loss). CFH may also have a pharmacogenetic role by affecting treatment response to widely used nutritional supplements. This paper examines other AMD susceptibility genes to determine if these genotypes influenced disease progression and treatment response. METHODS: Three cohorts, totalling 3137 individuals, were genotyped for SNPs in 13 genes previously published to be associated with advanced AMD (other than CFH and LOC387715/ARMS2/HTRA1). Those genes found associated were then evaluated for their involvement in disease progression. Interactions between the genes and with AREDS (Age-Related Eye Disease Study) nutritional supplements were investigated. RESULTS: Positive independent associations were noted in SNPs in the genes C2 (p = 0.0001, odds ratio (OR) 0.35, 95% confidence interval (CI) 0.2 to 0.6), CFB (p = 0.0001, OR 0.35, 95% CI 0.2 to 0.6), C3 (p = 0.0001, OR 3.91, 95% CI 1.94 to 7.88), APOE (epsilon4, p = 0.01, OR 0.50, 95% CI 0.29 to 0.86) and VEGFA (p = 0.01, OR 2.23, 95% CI 1.06 to 4.68). C2/CFB and C3 were independently related to progression from early/intermediate to advanced AMD with OR 0.32 (95% CI 0.14 to 0.73) and 3.32 (95% CI 1.46 to 7.59), respectively. Gene-gene and pharmacogenetic interactions were not observed. No preferential associations were observed with geographic atrophy or choroidal neovascularisation. CONCLUSION: This study provides insights into the genetic pathogenesis of AMD. Five genes have now been shown to be independently involved in progression from intermediate disease (before vision loss has occurred) to advanced disease in which blindness is frequent.

Bonilha VL, Trzupek KM, Li Y, Francis PJ, Hollyfield JG, Rayborn ME, Smaoui N, Weleber RG. · The Cleveland Clinic Foundation, The Cole Eye Institute, Cleveland, Ohio 44195, USA. · Ophthalmic Genet. · Pubmed #18766988 No free full text.

Abstract: PURPOSE: To define the retinal pathology in a 91 year-old affected matriarch of a three-generation choroideremia family with multiple manifesting carriers. METHODS: Tissue from three different retinal areas was processed for immunohistochemistry. The macular area was processed for transmission electron microscopy. Cryosections were studied by indirect immunofluorescence, using well-characterized antibodies to cone cytoplasm, rhodopsin and cone opsins. The affected donor eyes were compared to a postmortem matched normal eye. RESULTS: The retina displayed areas of severe degeneration, with no photoreceptor outer segments, photoreceptor nuclear atrophy, and atrophy of the inner retina. Other retinal areas were near to normal. The RPE was severely degenerated, with thinning, pigment clumping and sub-epithelial debris deposition in all the areas examined. The choroid displayed depigmentation. Labeling with cone opsin antibodies revealed that cones were drastically affected: blue opsin was almost completely absent, while red/green opsins were distributed along the entire plasma membrane of the cell. Rhodopsin was also distributed along the entire rod plasma membrane. Ultrastructural analysis of the affected macula revealed the absence of RPE apical microvilli and basal infoldings. Instead, RPE's basal surface and choroid displayed the presence of banded fibers composed of clumps of wide-spacing collagen. Bruch's membrane was filled with vesicular structures, some smooth and others with bristle-like projections. CONCLUSIONS: The histological data suggests that the clinical manifestation in this donor is related to degenerative changes in the retina, RPE, and choroid.

Francis PJ, Schultz DW, Hamon S, Ott J, Weleber RG, Klein ML. · Macular Degeneration Center, Casey Eye Institute, Oregon Health & Science University, Portland, Oregon, United States of America. · PLoS One. · Pubmed #18043728 links to  free full text

Abstract: BACKGROUND: Age-related macular degeneration (AMD), the leading cause of blindness in the Western world, is a complex disease that affects people over 50 years old. The complement factor H (CFH) gene has been repeatedly shown to be a major factor in determining susceptibility to the advanced form of the condition. We aimed to better understand the functional role of this gene in the AMD disease process and assess whether it is associated with earlier forms of the disease. METHODOLOGY/PRINCIPAL FINDINGS: WE genotyped SNPS at the cfh gene locus in three independent populations with AMD: (a) extended families where at least 3 family members had AMD; (b) sporadic cases of advanced AMD and (c) cases from the Age-Related Eye Disease Study (AREDS). We investigated polymorphisms and haplotypes in and around the CFH gene to assess their role in AMD. CFH is associated with early/intermediate and advanced AMD in both familial and sporadic cases. In our populations, the CFH SNP, rs2274700, is most strongly associated with AMD and when incorporated into a haplotype with the Y402H SNP and rs1061147, the strongest association is observed (p<10(-9)). CONCLUSIONS/SIGNIFICANCE: Our results, reproduced in three populations that represent the spectrum of AMD cases, provide evidence that the CFH gene is associated with drusen as well as with advanced AMD. We also identified novel susceptibility and protective haplotypes in the AMD populations.

Trzupek KM, Falk RE, Demer JL, Weleber RG. · Casey Eye Institute and Department of Ophthalmology, Oregon Health & Science University, Portland, Oregon 97239, USA. · Am J Med Genet A. · Pubmed #17486591 No free full text.

Abstract: Microcephaly with chorioretinopathy (OMIM 156590) is an autosomal dominant syndrome, characterized primarily by chorioretinal lesions and microcephaly. The phenotype is variable, and has been described in association with retinal dysplasia that can be stable or show progressive degeneration, retinal folds, lymphedema, and mental retardation. We describe two siblings with microcephaly, mental retardation, and variable retinal and choroidal abnormalities. Patient 1 has multiple atrophic and dysplastic-appearing lesions of the retina and choroid in each eye. An ERG at 5 months of age disclosed markedly subnormal scotopic and photopic responses with delayed flicker timing. Patient 2 has bilateral macular folds with vitreoretinopathy, serous retinal detachments, glaucoma, and cataracts OU. Both have mental retardation with hypotonia and severe microcephaly. Chorioretinopathy and retinal folds have been described independently in microcephaly with chorioretinopathy. The present sibs are the first in whom these features are observed while the parents are normal. Our findings support an expansion of the ocular phenotype and suggest the existence of germ line mosaicism.

Francis PJ, George S, Schultz DW, Rosner B, Hamon S, Ott J, Weleber RG, Klein ML, Seddon JM. · Macular Degeneration Center, Casey Eye Institute, Oregon Health and Science University, Portland, OR 97239, USA. · Hum Hered. · Pubmed #17347568 links to  free full text

Abstract: BACKGROUND AND AIMS: Age-related macular degeneration (AMD) is the leading cause of blindness in the Western World. It is now evident that both genetic and environmental factors contribute to disease susceptibility. We tested the hypotheses that (a) a common coding SNP in the LOC387715 gene is associated with advanced AMD (geographic atrophy or choroidal neovascularization), and (b) that modifiable environmental exposures alter AMD susceptibility associated with this SNP. METHODS: A case-control association analysis was performed on participants (530 advanced AMD cases and 280 controls) ascertained as part of the multi-center Age-Related Eye Disease Study. AMD status was determined by the reading center from fundus photographs using the AREDS AMD grading categorization. Environmental risk factor exposure data was collected from participants whose DNA was also genotyped for the LOC387715 gene SNP rs10490924. Multivariate logistic regression analyses were performed. RESULTS AND CONCLUSIONS: The number of risk alleles at the LOC387715 SNP was associated with advanced AMD, with odds ratios (OR) = 3.0 (95% confidence interval (CI) 2.1-4.3) for the GT heterozygous genotype and OR = 12.1 (5.6-26.5) for the homozygous TT risk genotype, after controlling for demographic and behavioral risk factors. The LOC387715 SNP was associated with both forms of advanced AMD. Current cigarette smoking and body mass index were independently related to AMD, controlling for genotype. However, there was no statistical interaction between LOC387715 genotype and smoking with regard to advanced AMD development.

Barral S, Francis PJ, Schultz DW, Schain MB, Haynes C, Majewski J, Ott J, Acott T, Weleber RG, Klein ML. · Laboratory of Statistical Genetics, Rockefeller University, New York, New York, USA. · Invest Ophthalmol Vis Sci. · Pubmed #17122136 links to  free full text

Abstract: PURPOSE: To investigate further the genetic contribution to age-related macular degeneration (AMD), increasing the power of a previous analysis and reproducing the original findings. METHODS: A large cohort of families with this condition was assembled, and an expanded genome scan was performed with 556 microsatellite markers. In 2003, the results were reported of a genome-wide linkage analysis of 70 of these pedigrees. Members of 51 new families have now been ascertained and many of the original pedigrees expanded. Parametric and nonparametric linkage analyses were performed with a denser map of markers. In addition, analyses were performed with the sample stratified by age at ascertainment and by two major advanced phenotypes for the disease: neovascular AMD (choroidal neovascularization) and geographic atrophy. RESULTS: The results corroborate the macular degeneration-susceptibility loci consistently reported by the authors and others in genome-wide scans. New loci were identified, including the finding of a two-point HLOD of 3.70 at 6q25.2. CONCLUSIONS: The results suggest that the use of families enriched in predisposition to AMD has legitimacy. Genetic analyses of a genome-wide scan performed on our large cohort of families add further confirmatory evidence that susceptibility loci lie on 1q, 3p, 9q, and 10q. Furthermore, new loci have been identified, including a locus on 6q.

Francis PJ, Schultz DW, Gregory AM, Schain MB, Barra R, Majewski J, Ott J, Acott T, Weleber RG, Klein ML. · Macular Degeneration Center, Casey Eye Institute, Oregon Health and Science University, 3375 SW Terwilliger Blvd, Portland, OR 97239-4197, USA. · Br J Ophthalmol. · Pubmed #16113362 links to  free full text

Abstract: BACKGROUND: The pattern dystrophies (PD) represent a clinically heterogeneous family of inherited macular diseases frequently caused by mutations in the peripherin/RDS gene. Most previous studies have detailed the clinical findings in single families, making it difficult to derive data from which progression and visual outcome can be generalised. METHODS: Families were ascertained and clinically evaluated including angiography and electrophysiology where appropriate. RESULTS: In each of the six families with autosomal dominant PD, a mutation in the peripherin/RDS gene was identified, including a novel Cys250Phe variant. These data suggest that the condition is characterised by the accumulation of yellow to grey subretinal flecks, followed by pigmentary change accompanied by patches of chorioretinal atrophy. Subsequently, 50% (16/32) of individuals with PD developed poor central vision because of chorioretinal geographic atrophy or subretinal neovascularisation. The risk of these complications appears to increase with age. CONCLUSION: PD should not necessarily be considered a benign condition. Instead, patients should be counselled that there is a significant chance of losing central vision in their later years. Some elderly patients with probands showing PD may be misdiagnosed with age related macular degeneration owing to the phenotypic similarities between these conditions in the advanced state.

Oh KT, Weleber RG, Stone EM, Oh DM, Rosenow J, Billingslea AM. · Department of Ophthalmology, University of North Carolina, Chapel Hill, North Carolina, USA. · Retina. · Pubmed #15579991 No free full text.

Abstract: PURPOSE: To characterize the clinical and electroretinogram (ERG) features of our cohort of patients with Stargardt disease (STGD) exhibiting coding sequence variations in the ABCA4 gene. METHODS: Review of 76 patients with the clinical diagnosis of Stargardt disease/fundus flavimaculatus (STGD/FF) from the University of Iowa Department of Ophthalmology and Visual Sciences (41 patients) and the Casey Eye Institute (35 patients). Clinical examination, Goldmann perimetry, and electroretinography were performed on all 76 patients. Patients were divided into three groups on the basis of their funduscopic and electroretinographic features: (1) a normal ERG by the standards of the laboratory; (2) minimal rod or cone abnormalities; (3) severe ERG dysfunction. The latter category was further subdivided on the basis of a cone-dominated loss of function (C > R or "cone-rod dystrophy") or diffuse depression of rods and cones (C = R). Mutational analysis of the coding sequence of the ABCA4 gene was performed by single strand conformation polymorphism analysis followed by automated DNA sequencing. Each electroretinographic group was analyzed for the presence of disease causing changes using exact tests of binomial proportions corrected for multiple comparisons by Bonferroni method. Quantitative polymerase chain reaction (QPCR) was performed on patients who were homozygous for disease causing changes in the ABCA4 gene to rule out the possibility of deletions. RESULTS: Overall, 56 of 76 patients (and 77 of 152 alleles) exhibited coding sequence variations that were compatible with high-penetrance disease-causing mutations. The most common of these were His423Arg (9), frameshift mutations (7), Ala1038Val (7), and Pro1380Leu (6). Although no patients with His423Arg presented with normal ERGs, no significant correlation was observed between specific sequence variations and the electroretinographic characteristics or fundus appearance. However, a significantly greater fraction of patients with normal ERG studies failed to exhibit detectable disease-causing coding sequence variations in the ABCA4 gene identified on either allele (P = 0.0006). CONCLUSION: STGD/FF patients in our cohort exhibit a wide range of electroretinographic abnormalities, some of which are more prevalent than previously suspected. No direct correlation between clinical appearance, electrophysiologic characteristics and specific ABCA4 alleles could be identified, although a significantly lower number of our cohort with a normal ERG exhibited detectable coding sequence variations in the ABCA4 gene. However, four patients with ERG dysfunction were homozygous for a His423Arg change proven by QPCR not to be an artifact of a deletion. The presence of electrophysiologic dysfunction is not uncommon in our cohort of patients with STGD. Thus, the ERG provides clinically important information of retinal function for STGD/FF and, as such, is still indicated as part of the evaluation of these patients.

Oh KT, Weleber RG, Oh DM, Billingslea AM, Rosenow J, Stone EM. · Department of Ophthalmology, University of North Carolina, Chapel Hill, NC, USA. · Retina. · Pubmed #15097887 No free full text.

Abstract: PURPOSE: To determine the prognostic significance of widespread flecks, described as fundus flavimaculatus, in patients with Stargardt disease. DESIGN: Historical cohort study. SUBJECTS AND METHODS: Patients with Stargardt disease were identified by searching preexisting databases at the University of Iowa and Oregon Health Sciences University. The medical records of these patients were evaluated for the validity of the diagnosis, initial and final visual acuity, length of follow-up, and initial and final phenotype. Phenotype was graded as I, II, or III on the basis of the distribution of flecks and the extent of atrophy. The relationship between final visual acuity and final clinical appearance (phenotype I versus II versus III) was evaluated controlling for length of follow-up and age using a Cochran-Mantel-Haenszel test. The clinical progression of visual acuity loss for each phenotype was analyzed using life tables and Kaplan-Meier survival analysis for age and length of follow-up effects. RESULTS: A total of 214 patients were confirmed to have Stargardt disease; 131 patients were seen at multiple visits. Eighty-two patients were identified with phenotype I, 62 with phenotype II, and 70 with phenotype III. The final visual outcome was significantly better for patients whose ophthalmoscopic abnormalities were limited to the macula (phenotype I): 80 of 82 patients with phenotype I (97.6%) maintained 20/200 or better visual acuity in at least one eye as compared to 40/62 (64.5%) patients with phenotype II and 13/70 (18.6%) patients with phenotype III (P < 0.0001). Survival analysis showed a similarly significant difference in the survival probabilities (likelihood of maintaining 20/200 or better vision) for the three phenotypes considered over age and over follow-up length (P < 0.0001), with phenotypes II and III demonstrating significantly more deterioration in vision over time. CONCLUSIONS: The presence of midperipheral flecks, especially early in life, carries a poorer visual prognosis for patients with Stargardt disease than when disease is limited to the macula. The development of midperipheral flecks is an indicator of more extensive fundus involvement and thus poorer long-term visual prognosis.

Schultz DW, Klein ML, Humpert AJ, Luzier CW, Persun V, Schain M, Mahan A, Runckel C, Cassera M, Vittal V, Doyle TM, Martin TM, Weleber RG, Francis PJ, Acott TS. · Macular Degeneration Center, Casey Eye Institute, Portland, OR 97239-4197, USA. · Hum Mol Genet. · Pubmed #14570714 links to  free full text

Abstract: Age-related macular degeneration (AMD) is a common cause of severe vision loss. Identification of the genes involved in AMD will lead to a better understanding of this disease at the molecular level, which will eventually lead to early detection, prevention and treatment. Previously, we mapped the ARMD1 gene to 1q25-31 in a large family with AMD. Here, we narrow the ARMD1 locus to 14.9 Mb between LAMB2 and D1S3469, a region containing 50 known genes. Twenty candidate genes within this region were screened for mutations. Only one DNA variation, an A16,263G transition in exon 104 of HEMICENTIN-1, was found to segregate exclusively with the disease haplotype in members of this large family with AMD. This variation produces a non-conservative substitution of arginine for glutamine at amino acid position 5345 (Gln5345Arg). It was also identified in 11 other individuals, all of whom share a haplotype, which envelops HEMICENTIN-1, with the large AMD family. The affected status of all but one of those individuals conforms to the age-dependent penetrance observed in AMD. The amino acid at position 5345 of HEMICENTIN-1 was conserved as glutamine in eight species analyzed. RT-PCR analysis demonstrated that exon 104 of HEMICENTIN-1 is alternatively spliced in various cell types. Exclusive segregation of Gln5345Arg with the disease haplotype in this large family, amino acid conservation of glutamine at this position among mammals, the non-conservative nature of the substitution and similarities to EFEMP1 support the conclusion that HEMICENTIN-1 is the ARMD1 gene.

Majewski J, Schultz DW, Weleber RG, Schain MB, Edwards AO, Matise TC, Acott TS, Ott J, Klein ML. · Laboratory of Statistical Genetics, Rockefeller University, New York, NY, USA. · Am J Hum Genet. · Pubmed #12900797 links to  free full text

Abstract: We performed a genomewide scan and genetic linkage analysis, to identify loci associated with age-related macular degeneration (AMD). We collected 70 families, ranging from small nuclear families to extended multigenerational pedigrees and consisting of a total of 344 affected and 217 unaffected members available for genotyping. We performed linkage analyses using parametric and allele-sharing models. We performed the analyses on the complete pedigrees but also subdivided the families into nuclear pedigrees. Finally, to dissect potential genetic factors responsible for differences in disease manifestation, we stratified the sample by two major AMD phenotypes (neovascular AMD and geographic atrophy) and by age of affected family members at the time of our evaluation. We have previously demonstrated linkage between AMD and 1q25-31 in a single large family. In the combined sample, we have detected the following loci with scores exceeding a LOD=2 cutoff under at least one of the models considered: 1q31 (HLOD=2.07 at D1S518), 3p13 (HLOD=2.19 at D3S1304/D3S4545), 4q32 (HLOD=2.66 at D4S2368, for the subset of families with predominantly dry AMD), 9q33 (LODZlr=2.01 at D9S930/D9S934), and 10q26 (HLOD=3.06 at D10S1230). Using correlation analysis, we have found a statistically significant correlation between LOD scores at 3p13 and 10q26, providing evidence for epistatic interactions between the loci and, hence, a complex basis of AMD. Our study has identified new loci that should be considered in future mapping and mutational analyses of AMD and has strengthened the evidence in support of loci suggested by other studies.

Schultz DW, Klein ML, Humpert A, Majewski J, Schain M, Weleber RG, Ott J, Acott TS. · Casey Eye Institute, Oregon Health & Science University, Portland, 97239, USA. · Arch Ophthalmol. · Pubmed #12742846 No free full text.

Abstract: BACKGROUND: Previously, the epsilon 4 allele of apolipoprotein E (APOE) was reported to have a significant association with a decreased risk of age-related macular degeneration (AMD). In addition, the epsilon 2 allele of APOE was reported to be possibly associated with an increased risk of AMD. OBJECTIVE: To determine if APOE polymorphisms, previously reported to be associated with AMD, affect its expression in medium to large families, as well as in unrelated patients with AMD. METHODS: The APOE genotype was determined by HhaI restriction digests of polymerase chain reaction-amplified products in a collection of 259 affected and 207 unaffected individuals from 56 AMD families. Genotypes were determined similarly in a set of 104 unrelated AMD patients and in 113 unaffected control subjects. Diagnosis of AMD was based on clinical examination and evaluation of fundus photographs. Evidence of an association between alleles of APOE and AMD in families was tested by the following 4 statistical methods: chi2 analysis of simple allele counting, logistic regression analysis adjusting for age, construction of likelihood ratios of haplotype frequencies, and the pedigree disequilibrium test. RESULTS: None of the statistical methods used showed a significant association between the common alleles of APOE and AMD in our collection of families or in the set of unrelated AMD patients. CONCLUSIONS: No evidence was found to support an association between AMD in medium to large families and the epsilon 4 or epsilon 2 alleles of APOE. Neither was any evidence found for an association of APOE polymorphisms with the set of unrelated patients with AMD. However, a trend for a decreased risk of AMD associated with APOE epsilon 4 was observed in the set of unrelated patients with a family history of AMD.

Tarttelin EE, Gregory-Evans CY, Bird AC, Weleber RG, Klein ML, Blackburn J, Gregory-Evans K. · Department of Molecular Genetics, Imperial College School of Medicine, London, UK. · J Med Genet. · Pubmed #11389162 links to  free full text

Abstract: OBJECTIVE: Autosomal dominant drusen is of particular interest because of its phenotypic similarity to age related macular degeneration. Currently, mutation R345W of EFEMP1 and, in a single pedigree, linkage to chromosome 6q14 have been causally related to the disease. We proposed to investigate and quantify the roles of EFEMP1 and the 6q14 locus in dominant drusen patients from the UK and USA. DESIGN: Molecular genetic analysis. PARTICIPANTS: Ten unrelated families and 17 young drusen patients. MAIN OUTCOME MEASURES: Exons 1 and 2 of EFEMP1 were characterised by 5' rapid amplification of cDNA ends and direct sequencing. Exons 1-12 of EFEMP1 were then investigated for mutation by direct sequencing. A HpaII restriction digest test was constructed to detect the EFEMP1 R345W mutation. Marker loci spanning the two dominant drusen linked loci were used to generate haplotype data. RESULTS: Only seven of the 10 families (70%) and one of the 17 sporadic patients (6%) had the R345W mutation. The HpaII restriction digest test was found to be a reliable and quick method for detecting this. No other exonic or splice site mutation was identified. Of the three families without EFEMP1 mutation, two were linked to the 2p16 region. CONCLUSIONS: EFEMP1 R345W accounts for only a proportion of the dominant drusen phenotype. Importantly, other families linked to chromosome 2p16 raise the possibility of EFEMP1 promoter sequence mutation or a second dominant drusen gene at this locus. Preliminary haplotype data suggest that the disease gene at the 6q14 locus is responsible for only a minority of dominant drusen cases.

Webster AR, Héon E, Lotery AJ, Vandenburgh K, Casavant TL, Oh KT, Beck G, Fishman GA, Lam BL, Levin A, Heckenlively JR, Jacobson SG, Weleber RG, Sheffield VC, Stone EM. · Department of Ophthalmology, The University of Iowa College of Medicine, 200 Hawkins Drive, Iowa City, IA 52242, USA. · Invest Ophthalmol Vis Sci. · Pubmed #11328725 links to  free full text

Abstract: 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).

Donoso LA, Frost AT, Stone EM, Weleber RG, MacDonald IM, Hageman GS, Cibis GW, Ritter R, Edwards AO. · Department of Ophthalmology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390-9057. · Arch Ophthalmol. · Pubmed #11296022 links to  free full text

Abstract: OBJECTIVES: To characterize a disease-associated haplotype in 7 families with autosomal dominant Stargardt-like macular dystrophy and to determine whether these families share a common ancestor. METHODS: Twenty-five polymorphic DNA markers spanning known dominant Stargardt-like gene loci were used to determine the haplotype associated with disease. In addition, an extensive genealogical investigation searching for a common ancestor shared by all of the 7 families was performed. RESULTS: We clinically evaluated 171 patients and genotyped 145 samples. The same DNA haplotype on chromosome 6q16 was shared by all evaluated affected members within the 7 families. In addition, we were able to genealogically join all of the families into one larger family consisting of 31 branches and 2314 individuals. Twenty-seven branches have known living descendants, with 7 branches having affected family members. In addition, we refined the critical region for the gene to approximately 1000 kilobases (kb) and eliminated part or all of 9 candidate disease-causing genes. CONCLUSIONS: Our study indicates that most reported cases of autosomal dominant Stargardt-like macular dystrophy in North America are part of a single larger family associated with a gene locus on chromosome 6q16. Furthermore, the DNA haplotype associated with disease is useful in excluding individuals with phenotypically similar retinal conditions. CLINICAL RELEVANCE: The disease-associated haplotype allows for more accurate genetic counseling to be given to individuals with a Stargardt-like phenotype inherited in an autosomal dominant pattern.

Milam AH, Curcio CA, Cideciyan AV, Saxena S, John SK, Kruth HS, Malek G, Heckenlively JR, Weleber RG, Jacobson SG. · Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, USA. · Ophthalmology. · Pubmed #11097607 No free full text.

Abstract: PURPOSE: To clarify the pathogenesis of late-onset retinal degeneration (L-ORD), an autosomal dominant disorder characterized by thick deposits of lipid-rich material between the retinal pigment epithelium (RPE) and Bruch's membrane. STUDY DESIGN: Comparative clinicopathologic case report and case series. TISSUES: Eyes of an 82-year-old L-ORD eye donor and an age-matched control. SUBJECTS: Five descendants of the eye donor and his affected sister. METHODS: The eyes were processed for histopathologic examination, including electron microscopy and immunohistochemistry. Family members were examined clinically and with retinal function tests. RESULTS: The L-ORD eye had sub-RPE deposits that were positive for lipid, including esterified and unesterified cholesterol. The deposits were thinnest in the macula, which retained the highest percentage of photoreceptors. In the periphery, RPE thinning and photoreceptor loss correlated with thickness of the sub-RPE deposits. The eye donor was asymptomatic until his late 50s, when he developed problems with adapting to darkness. At age 68, the eye donor had normal acuity but a midperipheral scotoma and subnormal electroretinograms (ERGs); visual loss was progressive. The five descendants (at the time of examination ages 44-58) of the eye donor and his affected sister, who were at 50/50 risk of inheriting L-ORD, had normal ERGs, but four showed defects in dark adaptation. The dark adaptation abnormalities had a distribution similar to the thickness of the sub-RPE deposits in the eye donor, with slow kinetics in the midperiphery and normal kinetics centrally. CONCLUSIONS: The L-ORD donor eye differed from a previous case in the regional distribution of sub-RPE deposits and photoreceptors. In the next generation of this L-ORD family, the first expression of disease, abnormal dark adaptation, mirrored the regional distribution of the deposits in the donor eye. The fine structure and staining characteristics of the sub-RPE deposits in L-ORD resemble those in age-related macular degeneration and Sorsby fundus dystrophy.

Lotery AJ, Munier FL, Fishman GA, Weleber RG, Jacobson SG, Affatigato LM, Nichols BE, Schorderet DF, Sheffield VC, Stone EM. · Department of Ophthalmology, The University of Iowa College of Medicine, Iowa City 52242, USA. · Invest Ophthalmol Vis Sci. · Pubmed #10798642 links to  free full text

Abstract: 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.

Gao YQ, Danciger M, Longmuir R, Piriev NI, Zhao DY, Heckenlively JR, Fishman GA, Weleber RG, Jacobson SG, Stone EM, Farber DB. · Jules Stein Eye Institute, University of California Los Angeles School of Medicine, CA 90095-7008, USA. · Invest Ophthalmol Vis Sci. · Pubmed #10393054 links to  free full text

Abstract: PURPOSE: To screen the exons of the gene encoding the alpha'-subunit of cone cyclic guanosine monophosphate (cGMP>phosphodiesterase (PDE6C) for mutations in a group of 456 unrelated patients with various forms of inherited retinal disease, including cone dystrophy, cone-rod dystrophy, macular dystrophy, and simplex/multiplex and autosomal recessive retinitis pigmentosa. METHODS: The 22 exons of the PDE6C gene were screened for mutations either by denaturing gradient gel electrophoresis and single-strand conformation polymorphism electrophoresis (SSCP) or by SSCP alone; variants were sequenced directly. RESULTS: Although many sequence variants were found, none could be associated with disease. CONCLUSIONS: The results show that PDE6C was not the site of the amutations responsible for the types of inherited retinal degenerations analyzed in the large population of patients 'in the present study. The types of degeneration included those that predominantly affect cone-mediated function (cone and cone-rod dystrophies) or rod-mediated function (retinitis pigmentosa) or that have a predilection for disease in the macula (macular dystrophies).

Edwards AO, Miedziak A, Vrabec T, Verhoeven J, Acott TS, Weleber RG, Donoso LA. · Casey Eye Institute, Department of Ophthalmology, Oregon Health Sciences University, Portland, USA. · Am J Ophthalmol. · Pubmed #10218695 No free full text.

Abstract: PURPOSE: Characterize the phenotype of autosomal dominant Stargardt-like macular dystrophy in two families linked to chromosome 6q14 and determine whether they share a common ancestry. METHODS: Two families spanning 10 generations were identified and studied independently. Participating members were examined and genetic linkage and genotyping performed. RESULTS: Presenting symptoms included decreased vision, hemeralopia, and mild photophobia. The subjective onset of visual loss ranged from age 3 to 50 with a mean of 14 years. A Snellen acuity of 20/200 occurred at a mean age of 22 years. Over decades, the macular lesion enlarged and visual acuity decreased to 20/300 to 20/800. The typical phenotype was well-circumscribed, homogenous atrophy of the retinal pigment epithelium and choriocapillaris in the macula, with surrounding yellow flecks and temporal optic nerve pallor. The phenotypic spectrum included a pattern dystrophy-like appearance, diffuse geographic atrophy, and extensive fundus flecks. Genotyping revealed that the two families were linked to chromosome 6q14 and shared a common haplotype spanning 21 cM between D6S430 and D6S300. The two families were subsequently shown by genealogic investigation to represent different branches of a common kindred. CONCLUSIONS: Families with autosomal dominant Stargardt-like macular dystrophy linked to chromosome 6q14 share a common phenotype and in some cases can be distinguished from similar dystrophies by inheritance pattern and clinical features. The finding that these two families shared a common ancestor suggests the existence of a founder effect. Characterization of the gene for autosomal dominant Stargardt-like macular dystrophy may enable better understanding of this condition and elucidation of its potential role in other forms of macular degeneration.