A G1103R mutation in CRB1 is co-inherited with high hyperopia and Leber congenital amaurosis.

PURPOSE: To identify the genetic basis of recessive inheritance of high hyperopia and Leber congenital amaurosis (LCA) in a family of Middle Eastern origin. MATERIALS AND METHODS: The patients were examined using standard ophthalmic techniques. DNA samples were obtained and genetic linkage was carried out using polymorphic markers flanking the known genes and loci for LCA. Exons were amplified and sequenced. RESULTS: All four members of this family affected by LCA showed high to extreme hyperopia, with average spherical refractive errors ranging from +5.00 to +10.00. Linkage was obtained to 1q31.3 with a maximal LOD score of 5.20 and a mutation found in exon 9 of the CRB1 gene, causing a G1103R substitution at a highly conserved site in the protein. CRB1 is a vertebrate homolog of the Drosophila crumbs gene, which is required for photoreceptor morphogenesis, and has been associated with either retinitis pigmentosa (RP) or LCA. This sequence variant has previously been reported as a compound heterozygote in one sporadic LCA patient. CONCLUSION: Although hyperopia has been associated with LCA, it is typically moderate and variable between patients with the same mutation. In addition, some CRB1 mutations can be associated with either RP or LCA. We have shown that hyperopia and LCA are linked to the mutant CRB1 gene itself and are not dependent on unlinked modifiers.

Clinical and genetic analysis of a family with X-linked congenital nystagmus (NYS1).

PURPOSE: To describe a family with X-linked congenital nystagmus and identify the genetic interval within which the gene is located. METHODS AND DESIGN: Clinical examination with genotyping of 30 individuals from a multi-generational Caucasian family with congenital nystagmus inherited in an X-linked pattern using markers from Xq26-q27, followed by linkage analysis and sequencing of a candidate gene, solute carrier family 25, member 14 (SLC25A14), in four affected individuals from four families linked to this region. RESULTS: The pattern of inheritance in the family was consistent with X-linkage with incomplete penetrance among carrier females. No affected males had affected sons. Based on the extended pedigree, the estimated penetrance among obligate female carriers (daughters of affected males) was 29% (6 of 21). Visual acuity among 15 affected individuals ranged from 20/20 to 20/70 (median 20/30). Clinical examinations, including electroretinography in two individuals, were otherwise normal except for the presence of nystagmus. Significant LOD scores (theta = 0) were found with markers DXS8057, DXS8044, DXS1047, DXS1062, DXS8072, and DXS8078, placing the gene within a approximately 5 cM interval flanked by DXS9909 and DXS1211 on the long arm of the X chromosome. Sequencing the candidate gene SLC25A14 in four affected individuals from four families linked to this region failed to reveal any mutations. CONCLUSIONS: NYS1 appears to be a common gene for familial congenital idiopathic nystagmus. Linkage analysis of this family further reduces the interval in which NYS1 is located.

The ateliotic macula: a newly recognized developmental anomaly.

PURPOSE: We present a macular phenotype resulting from 1 or more abnormalities in the developmental pathway of the central retina. METHODS: We describe the clinical and genetic characteristics of 7 patients observed since shortly after birth with regard to visual acuity, refractive error, anterior segment status, retinal findings including foveal structure, and natural history. RESULTS: The patients varied in age from 18 months to 18 years. All patients were examined for the first time during their first year of life and by us at the age of 5 years or younger. The longest follow-up period was 16 years. The abnormal appearance of the macula consisted of thinning of the retina, rarefication of the pigment epithelium with excess visibility of the large choroidal vessels, and absence of the foveal reflex. The visual acuities varied from 20/20 in the better eye to light perception. A retinal detachment was noted in 1 patient at age 2 1/2 years. The refractive errors varied from -2.50 to -16.50 diopters of spherical equivalent. The disease was limited to the retina in 4 patients. In 2 patients, however, developmental abnormalities of the anterior segment were also present; they consisted of malformation of the iris in 1 patient and Peters' anomaly in the other. The electroretinogram (ERG) showed reduced but not absent photopic responses and some reduction in scotopic responses. CONCLUSION: The phenotype of ateliotic macula is being defined as characterized by an unfinished or primordial appearance. In the 7 patients studied, visual loss was noted shortly after birth. The visual outcome was variable with regard to visual acuity, but many patients showed improvement. There was no evidence of significant worsening of the disease with age except in 1 patient who had a retinal detachment. The ERG responses showed primarily photopic but also scotopic changes. The better-preserved ERG differentiates this disorder from Leber's congenital amaurosis.

A case-control study of tobacco and alcohol consumption in Leber hereditary optic neuropathy.

PURPOSE: To determine if tobacco or alcohol consumption is associated with vision loss among sibships harboring pathogenic mitochondrial mutations associated with Leber hereditary optic neuropathy. METHODS: Retrospective case-control study with questionnaires obtained from both affected and unaffected siblings from 80 sibships with Leber hereditary optic neuropathy. Sibships harbored molecularly confirmed mitochondrial DNA mutations at nucleotide positions 11778 (63), 14484 (10), and 3460 (7). Exposure in affected individuals was calculated based on reported consumption before vision loss. RESULTS: For male probands (67 sibships), the recurrence risk within a sibship was 10.3% (eight of 78) for males and 3.1% (three of 98) for females. For female probands (13 sibships), the recurrence risk within a sibship was 17.6% (three of 17) for males and 0% (zero of 22) for females. Greater risk of vision loss was associated with male sex (odds ratio [OR] = 6.63; 95% confidence interval [CI] = 2.96 to 14.84; P =.00001) and harboring a 3460 or 14484 in comparison with the 11778 mutation (OR = 2.071; 95% CI = 1.19 to 3.58; P =.0095). No significant association of maximal intensity of smoking or cumulative smoking, whether light or heavy, with vision loss was observed. Light (OR = 0. 31; 95% CI = 0.17 to 0.56; P =.0001) and heavy alcohol consumers (OR = 0.25; 95% CI = 0.11 to 0.58; P =.0011) were less likely to be affected than individuals who did not consume alcohol after adjusting for age, sex, and mutation. In a categorical analysis of sibships with the 3460 or 14484 mutation, no relationship of vision loss with tobacco or alcohol consumption was observed. CONCLUSION: Unlike previous studies, the present study calculated exposure based on self-reported consumption of tobacco or alcohol before vision loss. No significant deleterious association between tobacco or alcohol consumption and vision loss among individuals harboring Leber hereditary optic neuropathy mutations was observed. Tobacco and alcohol do not appear to promote vision loss in Leber hereditary optic neuropathy.

Mutational analysis and clinical correlation in Leber congenital amaurosis.

UNLABELLED: Leber congenital amaurosis (LCA, MIM 204001) is a clinically and genetically heterogeneous retinal disorder characterized by severe visual loss from birth, nystagmus, poor pupillary reflexes, retinal pigmentary or atrophic changes, and a markedly diminished electroretinogram (ERG). PURPOSE: To examine 100 consecutive patients with LCA in order to assess the relative burden of the three known genes involved in LCA, namely retinal guanylyl cyclase (GUCY2D), retinal pigment epithelium protein ( RPE65), and the cone-rod homeobox (CRX), and to define their clinical correlates. METHODS: Mutational analysis and detailed clinical examinations were performed in patients diagnosed with LCA at the Johns Hopkins Center for Hereditary Eye Diseases and the Montreal Children's Hospital. RESULTS: Mutations were identified in 11% of our patients: GUCY2D mutations accounted for 6%, while RPE65 and CRX gene mutations accounted for 3% and 2%, respectively. The clinical presentation was variable; however, the visual evolution in patients with mutations in GUCY2D and CRX remained stable, while individuals with mutations in the RPE65 gene showed progressive visual loss. CONCLUSIONS: This study suggests that molecular diagnosis of Leber congenital amaurosis could provide important information concerning prognosis and course of treatment.

Retinal detachment in Marfan syndrome.

PURPOSE: To report postsurgical findings in patients with Marfan syndrome and retinal detachment (RD). METHODS: The authors identified and retrospectively reviewed the charts of one cohort of 12 patients (15 eyes) with Marfan syndrome and RD who were operated on at the Wilmer Institute and a second cohort of 16 such patients (24 eyes) who were operated several years earlier and elsewhere. RESULTS: First cohort--Final visual acuity (VA) was 20/80 or better and the retina was flat in all five phakic eyes (100%). The RD occurred after the eye had undergone lens removal in 10 eyes, 6 of which (60%) had a final VA of 20/80 or better, and 9 of which (90%) had a final VA of 5/200 or better (P = 0.20). Second cohort--The final VA was 20/80 or better and the retina was flat in 6 of the 7 phakic eyes (86%). Among 17 aphakic or pseudophakic eyes, only 5 (29%) had a flat retina and VA of 20/80 or better, whereas 12 (71%) had no light perception (P = 0.03). CONCLUSIONS: The results of RD operations done in the past in Marfan patients were worse when the eye was aphakic. In most cases operated more recently, the prognosis for successful RD repair was good regardless of whether the eye was phakic.

A CRX null mutation is associated with both Leber congenital amaurosis and a normal ocular phenotype.

PURPOSE: To identify and characterize new cone rod homeobox (CRX) mutations associated with the Leber congenital amaurosis phenotype. METHODS: The human CRX gene was sequenced in 74 consecutive patients carrying the diagnosis of Leber congenital amaurosis. RESULTS: Two mutations were identified in CRX that cause frameshifts and predict severe truncations of the encoded protein. One of these, a 1-bp insertion, spares only nine N-terminal amino acids, removing the homeodomain, WSP motif, and conserved OTX domain at the C terminus. Of the CRX mutations described in the literature, this is the first that convincingly represents a null allele of the gene. Although the patient heterozygous for this null allele is affected with Leber congenital amaurosis, it was surprising that her father, who had normal vision, was heterozygous for the same mutation. CONCLUSIONS: These results strongly suggest that haploinsufficiency of CRX is not sufficient to cause a retinal disorder. Loss of function alleles of CRX appear to cause Leber congenital amaurosis through a recessive or multigenic mechanism.

Genetic basis of total colourblindness among the Pingelapese islanders.

Complete achromatopsia is a rare, autosomal recessive disorder characterized by photophobia, low visual acuity, nystagmus and a total inability to distinguish colours. In this disease, cone photoreceptors, the retinal sensory neurons mediating colour vision, seem viable but fail to generate an electrical response to light. Achromatopsia, or rod monochromatism, was first mapped to 2p11-2q12 (MIM 216900; ref. 3), where it is associated with missense mutations in CNGA3 (ref. 4). CNGA3 encodes the alpha-subunit of the cone cyclic nucleotide-gated cation channel, which generates the light-evoked electrical responses of cone photoreceptors. A second locus at 8q21-q22 has been identified among the Pingelapese islanders of Micronesia, who have a high incidence of recessive achromatopsia (MIM 262300). Here we narrow the achromatopsia locus to 1.4 cM and show that Pingelapese achromatopsia segregates with a missense mutation at a highly conserved site in CNGB3, a new gene that encodes the beta-subunit of the cone cyclic nucleotide-gated cation channel. Two independent frameshift deletions establish that achromatopsia is the null phenotype of CNGB3. Combined with earlier findings, our results demonstrate that both alpha- and beta-subunits of the cGMP-gated channel are essential for phototransduction in all three classes of cones.

Prevalence of AIPL1 mutations in inherited retinal degenerative disease.

Leber congenital amaurosis (LCA) is the most severe form of inherited retinal dystrophy and the most frequent cause of inherited blindness in children. LCA is usually inherited in an autosomal recessive fashion, although rare dominant cases have been reported. One form of LCA, LCA4, maps to chromosome 17p13 and is genetically distinct from other forms of LCA. We recently identified the gene associated with LCA4, AIPL1 (aryl-hydrocarbon interacting protein-like 1) and identified three mutations that were the cause of blindness in five families with LCA. In this study, AIPL1 was screened for mutations in 512 unrelated probands with a range of retinal degenerative diseases to determine if AIPL1 mutations cause other forms of inherited retinal degeneration and to determine the relative contribution of AIPL1 mutations to inherited retinal disorders in populations worldwide. We identified 11 LCA families whose retinal disorder is caused by homozygous or compound heterozygous AIPL1 mutations. We also identified affected individuals in two apparently dominant families, diagnosed with juvenile retinitis pigmentosa or dominant cone-rod dystrophy, respectively, who are heterozygous for a 12-bp AIPL1 deletion. Our results suggest that AIPL1 mutations cause approximately 7% of LCA worldwide and may cause dominant retinopathy.

Microfibril abnormalities of the lens capsule in patients with Marfan syndrome and ectopia lentis.

PURPOSE: To determine the distribution and structure of fibrillin microfibrils in the three fibrillin-rich lens capsule zones of subjects with the Marfan syndrome. METHODS: Capsules were dissected from nine lenses extracted intracapsularly from Marfan syndrome patients. The capsules were divided and mounted flat on gelatin-coated glass slides. ABC immunoperoxidase staining with monoclonal anti-fibrillin antibody was used to visualize and localize fibrillin in these specimens. The staining patterns and microscopic structure of microfibrils were compared to those of normal controls. RESULTS: There were no bundles of fibrillin fibers in Zone I - a 0.75-mm wide peripheral ring of the anterior capsule that normally contains radial bunches of fibrillin fibers; instead, fine disorganized fibrillin-positive fragments were dispersed in this region. The size and shape of the fragments varied among patients. In contrast to normal lenses, there was only light staining for fibrillin in Zone II - a 1-mm wide meshwork of normally fibrillin-rich fibers that encircles the equator and serves as an insertion platform for most zonular fibers. The radial periodic bands of Zone III - a 0.1-mm wide ring on the most peripheral part of the normal posterior capsule - were identifiable in some samples, but stained only faintly for fibrillin. CONCLUSION: Fibrillin microfibrils are disrupted and fragmented in the lens capsule of patients with the Marfan syndrome. The qualitative, quantitative, and structural abnormalities of fibrillin deposition in the lens capsule of these patients support a causal relationship to lens abnormalities in this disease.

Orthostatic intolerance and chronic fatigue syndrome associated with Ehlers-Danlos syndrome.

OBJECTIVE: To report chronic fatigue syndrome (CFS) associated with both Ehlers-Danlos syndrome (EDS) and orthostatic intolerance. STUDY DESIGN: Case series of adolescents referred to a tertiary clinic for the evaluation of CFS. All subjects had 2-dimensional echocardiography, tests of orthostatic tolerance, and examinations by both a geneticist and an ophthalmologist. RESULTS: Twelve patients (11 female), median age 15.5 years, met diagnostic criteria for CFS and EDS, and all had either postural tachycardia or neurally mediated hypotension in response to orthostatic stress. Six had classical-type EDS and 6 had hypermobile-type EDS. CONCLUSIONS: Among patients with CFS and orthostatic intolerance, a subset also has EDS. We propose that the occurrence of these syndromes together can be attributed to the abnormal connective tissue in dependent blood vessels of those with EDS, which permits veins to distend excessively in response to ordinary hydrostatic pressures. This in turn leads to increased venous pooling and its hemodynamic and symptomatic consequences. These observations suggest that a careful search for hypermobility and connective tissue abnormalities should be part of the evaluation of patients with CFS and orthostatic intolerance syndromes.

Ocular anterior chamber dysgenesis in craniosynostosis syndromes with a fibroblast growth factor receptor 2 mutation.

Fibroblast growth factor receptor (FGFR) mutations have been found in craniosynostosis syndromes with and without limb and/or dermatologic anomalies. Ocular manifestations of FGFR2 syndromes are reported to include shallow orbits, proptosis, strabismus, and hypertelorism, but no ocular anterior chamber, structural abnormalities have been reported until now. We evaluated three unrelated patients with severe Crouzon or Pfeiffer syndrome. Two of them had ocular findings consistent with Peters anomaly, and the third patient had opaque corneae, thickened irides and ciliary bodies, and shallow anterior chambers with occluded angles. Craniosynostosis with and without cloverleaf skull deformity, large anterior fontanelle, hydrocephalus, proptosis, depressed nasal bridge, choanal stenosis/ atresia, midface hypoplasia, and elbow contractures were also present. These patients had airway compromise, seizures, and two died by age 15 months. All three cases were found to have the same FGFR2 Ser351Cys (1231C to G) mutation predicted to form an aberrant disulfide bond(s) and affect ligand binding. Seven patients with isolated Peters anomaly, two patients with Peters plus syndrome, and three cases with typical Antley-Bixler syndrome were screened for this mutation, but none was found. These phenotype/genotype data demonstrate that FGFR2 is involved in the development of the anterior chamber of the eye and that the Ser351Cys mutation is associated with a severe phenotype and clinical course.

Four polymorphic variations in the PEDF gene identified during the mutation screening of patients with Leber congenital amaurosis.

PURPOSE: Leber congenital amaurosis (LCA) has been mapped to chromosome 17p13.1. From the candidate genes mapped to this region, thus far, only Retinal Guanylate Cyclase (RetGC), has been found to have pathogenic LCA mutations, in families from North African origin. However, early reports, demonstrated eight LCA families linked to 17p13.1, but only four of them showed mutations in RetGC. Mapped in proximity to this locus is the candidate gene Pigment Epithelium Derived actor (PEDF), a factor implicated in photoreceptor differentiation and neuronal survival. Our purpose in this study was to identify mutations and polymorphisms in the PEDF gene in LCA patients of diverse ethnic origin. METHODS: Automated genotyping with four 17p13.1 markers flanking the PEDF gene was performed to assess homozygosity and PCR-SSCP combined with direct sequencing was used to detect mutations in the PEDF gene in 17 LCA patients. RESULTS: Homozygosity of markers D17S796 and D17S804 was found and four new intragenic basepair alterations were discovered: a Met72Thr polymorphism in exon 3 (T331C), a Thr130Thr polymorphism in exon 4 (T506C), a G to A transition in intron 5 (nine base pairs upstream from splice acceptor site), and a Tyr321Tyr polymorphism in exon 7 (C1079T) were detected. CONCLUSIONS: We report the discovery of four new polymorphic alterations in the PEDF gene in LCA patients and exclude by RFLP analysis the PEDF gene as a common cause of Leber congenital amaurosis. These single nucleotide polymorphisms will aid in future linkage analysis of complex multifactorial diseases involving retinal and RPE dysfunctions.

Genetic heterogeneity of dominant optic atrophy, Kjer type: Identification of a second locus on chromosome 18q12.2-12.3.

OBJECTIVE: To evaluate a family with autosomal dominant optic atrophy, which has been previously linked to the Kidd blood group. DESIGN: Clinical evaluation with the assessment of visual acuity, color vision, and optic nerve appearance to determine affection status. Linkage analysis using polymorphic DNA markers. RESULTS: Visual acuities ranged from 20/20 to 6/200. Although linkage was excluded for chromosome 3q28-29, markers from chromosome 18 in the vicinity of the Kidd locus were linked to the disorder (D18S34 [maximal lod score (lodmax) of 5.38 at recombination fraction (theta) of 0.14], D18S548 [lod(max)=7.26, theta=0.09], D18S861 [lod(max)= 5.32, theta = 0.07], and D18S479 [lod(max) = 3.28, 0 = 0.12:]). Multipoint linkage analysis demonstrated lod scores of greater than 3 in an approximately 3-centimorgan region flanked by D18S34 and D18S479, using 98% penetrance and a phenocopy rate of 1/50. CONCLUSIONS: Dominant optic atrophy is genetically heterogeneous, with loci assigned to chromosomes 3q28-29 and 18q12.2-12.3. Dominant optic atrophy linked to 18q shows intrafamilial variation similar to that previously reported in families linked to 3q, with visual acuities ranging from normal to legal blindness. The overall distribution of visual acuities appears more favorable with the 18q phenotype. Both phenotypes appear to have a similar rate of visual decline.

Bestrophin gene mutations in patients with Best vitelliform macular dystrophy.

Best vitelliform macular dystrophy (VMD2) is an autosomal dominant dystrophy with a juvenile age of onset. Mutations in the Bestrophin gene were shown in patients affected with VMD2. In a mutation study, we made three new and interesting observations. First, we identified possible mutation hotspots within the gene, suggesting that particular regions of the protein have greater functional significance than others. Second, we described a 2-bp deletion in a part of the gene where mutations have not previously been reported; this mutation causes a frameshift and subsequent premature termination of the protein. Finally, we have evidence that some mutations are associated with variable expression of the disease, suggesting the involvement of other factors or genes in the disease phenotype.

Congenital motor nystagmus linked to Xq26-q27.

Congenital motor nystagmus (CMN) is a hereditary disorder characterized by bilateral ocular oscillations that begin in the first 6 mo of life. It must be distinguished from those genetic disorders-such as ocular albinism (OA), congenital stationary night blindness (CSNB), and blue-cone monochromatism (BCM)-in which nystagmus accompanies a clinically apparent defect in the visual sensory system. Although CMN is presumed to arise from a neurological abnormality of fixation, it is not known whether the molecular defect is located in the eye or in the brain. It may be inherited in an autosomal dominant, autosomal recessive, or X-linked pattern. Three families with CMN inherited in an X-linked, irregularly dominant pattern were investigated with linkage and candidate gene analysis. The penetrance among obligate female carriers was 54%. Evaluation of markers in the region of the genes for X-linked OA, CSNB, and BCM revealed no evidence of linkage, supporting the hypothesis that CMN represents a distinct entity. The gene was mapped to chromosome Xq26-q27 with the following markers: GATA172D05 (LOD score 3.164; recombination fraction [theta] = 0.156), DXS1047 (LOD score 10.296; theta = 0), DXS1192 (LOD score 8.174; theta = 0.027), DXS1232 (LOD score 6.015; theta = 0.036), DXS984 (LOD score 6.695; theta = 0), and GATA31E08 (LOD score 4.940; theta = 0.083). Assessment of haplotypes and multipoint linkage analysis, which gave a maximum LOD score of 10.790 with the 1-LOD-unit support interval spanning approximately 7 cM, place the gene in a region between GATA172D05 and DXS1192. Evaluation of candidate genes CDR1 and SOX3 did not reveal mutations in affected male subjects.

Assessment of the interphotoreceptor matrix proteoglycan-1 (IMPG1) gene localised to 6q13-q15 in autosomal dominant Stargardt-like disease (ADSTGD), progressive bifocal chorioretinal atrophy (PBCRA), and North Carolina macular dystrophy (MCDR1).

We have recently characterised the genomic organisation of a novel interphotoreceptor matrix proteoglycan, IMPG1, and have mapped the gene locus to chromosome 6q13-q15 by fluorescence in situ hybridisation. As the interphotoreceptor matrix (IPM) is thought to play a critical role in retinal adhesion and the maintenance of photoreceptor cells, it is conceivable that a defect in one of the IPM components may cause degenerative lesions in retinal structures and thus may be associated with human retinopathies. By genetic linkage analysis, several retinal dystrophies including one form of autosomal dominant Stargardt-like macular dystrophy (STGD3), progressive bifocal chorioretinal atrophy (PBCRA), and North Carolina macular dystrophy (MCDR1) have previously been localised to a region on proximal 6q that overlaps the IMPG1 locus. We have therefore assessed the entire coding region of IMPG1 by exon amplification and subsequent single stranded conformational analysis in patients from 6q linked multigeneration families diagnosed with PBCRA and MCDR1, as well as a single patient from an autosomal dominant STGD pedigree unlinked to either of the two known STGD2 and STGD3 loci on chromosomes 13q and 6q, respectively. No disease associated mutations were identified. In addition, using an intragenic polymorphism, IMPG1 was excluded by genetic recombination from both the PBCRA and the MCDR1 loci. However, as the autosomal dominant Stargardt-like macular dystrophies are genetically heterogeneous, other forms of this disorder, in particular STGD3 previously linked to 6q, may be caused by mutations in IMPG1.