Optic disc morphology of patients with OPA1 autosomal dominant optic atrophy

BACKGROUND/AIMS: Patients with autosomal dominant optic atrophy (ADOA) are genetically heterogeneous, but all have disc pallor. A degree of cupping in ADOA can make the distinction from normal tension glaucoma (NTG) clinically difficult. This study aimed to clarify the features of the optic nerve of patients with ADOA at the OPA1 locus. METHODS: 29 patients (58 eyes), from 12 families, were identified in a prospective observational study of patients with ADOA examined by a single observer between 1995 and 1998, in whom genetic analysis showed either evidence for linkage to chromosome 3q28 or mutations in the ADOA gene, OPA1. All of the patients had disc and fundal photographs available for retrospective analysis. Clinical data collected included disc appearance, intraocular pressure, Snellen visual acuity, Hardy-Rand-Rittler colour vision plates, and Humphrey 30-2 visual fields. RESULTS: Mean age at time of examination was 37 years and mean visual acuity was 6/24. Disc morphology showed temporal disc pallor in 30 eyes (52%) and total disc pallor in 28 eyes (48%). At least one disc showed a cup to disc ratio of more than 0.5 in 18 patients (28 discs, 48%). The temporal neuroretinal rim always showed pallor and shallow shelving (or saucerisation) was seen in 46 eyes (79%). Only 12 discs (21%) had deep excavation and baring of blood vessels. All of the patients had normal intraocular pressure and no family history of glaucoma. There was a temporal grey, pigmentary crescent in 12 patients (18 eyes, 31%) and peripapillary atrophy in 20 patients (40 eyes, 69%), but disc margin haemorrhages were not seen. There was no maculopathy or retinopathy. CONCLUSION: The optic disc morphology, described for the first time in this genetically homogeneous population of patients with OPA1 ADOA, shows a distinctive absence of a healthy neuroretinal rim and shallow saucerisation of the optic disc cup, with frequent peripapillary atrophy.     

A comprehensive survey of mutations in the OPA1 gene in patients with autosomal dominant optic atrophy

PURPOSE: To characterize the spectrum of mutations in the OPA1 gene in a large international panel of patients with autosomal dominant optic atrophy (adOA), to improve understanding of the range of functional deficits attributable to sequence variants in this gene, and to assess any genotype-phenotype correlations. METHODS: All 28 coding exons of OPA1, intron-exon splice sites, 273 bp 5' to exon 1, and two intronic regions with putative function were screened in 94 apparently unrelated white patients of European origin with adOA by single-strand conformational polymorphism (SSCP)-heteroduplex analysis and direct sequencing. Clinical data were collated, and putative mutations were tested for segregation in the respective families by SSCP analysis or direct sequencing and in 100 control chromosomes. Further characterization of selected splice site mutations was performed by RT-PCR of patient leukocyte RNA. Staining of mitochondria in leukocytes of patients and control subjects was undertaken to assess gross differences in morphology and cellular distribution. RESULTS: Twenty different mutations were detected, of which 14 were novel disease mutations (missense, nonsense, deletion-frameshift, and splice site alterations) and six were known mutations. Mutations were found in 44 (47%) of the 94 families included in the study. Ten new polymorphisms in the OPA1 gene were also identified. Mutations occur throughout the gene, with three clusters emerging: in the mitochondrial leader, in the highly conserved guanosine triphosphate (GTP)-binding domain, and in the -COOH terminus. Examination of leukocyte mitochondria from two unrelated patients with splice site mutations in OPA1 revealed no abnormalities of morphology or cellular distribution when compared with control individuals. CONCLUSIONS: This study describes 14 novel mutations in the OPA1 gene in patients with adOA, bringing the total number so far reported to 54. It is likely that many cases of adOA are due to mutations outside the coding region of OPA1 or to large-scale rearrangements. Evaluation of the mutation spectrum indicates more than one pathophysiological mechanism for adOA. Preliminary data suggests that phenotype-genotype correlation is complex, implying a role for other genetic modifying or environmental factors. No evidence was found of pathologic changes in leukocyte mitochondria of patients with adOA.     

A novel mutation of the OPA1 gene responsible for isolated autosomal dominant optic atrophy in two brothers

Autosomal dominant optic atrophy, or Kjer disease, is the most frequent form of autosomal dominant optic neuropathy. We report a novel mutation of the OPA1 gene in two brothers with autosomal dominant optic atrophy and describe their clinical features. The two patients, aged 41 and 37, presented with a bilateral visual impairment that had been detected at the age of 4 in both of them. Their ophthalmoscopic examinations disclosed a bilateral optic atrophy and their Goldmann visual fields showed cecocentral scotomas. The patients thought their disease might be a Leber's hereditary optic neuropathy; however, mutations had ever been sought. When first seen by us, they wished to know whether their disorder might be transmitted to their children. They had a family history of visual impairment. We carried out mtDNA sequencing but we did not identify any primary or rare Leber's hereditary optic neuropathy mutations. On the other hand, the 30 coding exons of the OPA1 gene and the intron-exon junctions were amplified by polymerase chain reaction and sequenced. A novel mutation of the OPA1 gene was found in both brothers: a deletion of four nucleotides in intron 19, associated with anomalous splicing, demonstrating the pathogenicity of the mutation. These molecular analyses contributed to identifying a novel mutation of the OPA1 gene with a clinical phenotype of isolated optic atrophy.     

OPA1 mutations in Japanese patients suspected to have autosomal dominant optic atrophy

Purpose  

To report three types of heterozygous mutations in the OPA1 gene in five patients from three families with autosomal dominant optic atrophy (ADOA, MIM#165500).     

Pattern of retinal ganglion cell loss in dominant optic atrophy due to OPA1 mutations

Purpose

The majority of patients with autosomal dominant optic atrophy (DOA) harbour pathogenic OPA1mutations. Although DOA is characterised by the preferential loss of retinal ganglion cells (RGCs), about 20% of patients with OPA1mutations will develop a more severe disease variant (DOA+), with additional neuromuscular features. In this prospective, observational case series, optical coherence tomography (OCT) was used to define the pattern of retinal nerve fibre layer (RNFL) loss in patients with both the pure and syndromal forms of DOA.

Methods

Forty patients with a molecular diagnosis of DOA due to OPA1mutations were prospectively recruited from our neuro-ophthalmology clinic: 26 patients with isolated optic atrophy and 14 patients manifesting DOA+ features. Peripapillary RNFL thickness was measured with the Fast RNFL (3.4) acquisition protocol on a Stratus OCT.

Results

There was a statistically significant reduction in average RNFL thickness in the OPA1group compared with normal controls (P<0.0001). The percentage decrease was greatest in the temporal quadrant (59.0%), followed by the inferior (49.6%), superior (41.8%), and nasal (25.9%) quadrants. Patients with DOA+ features had worse visual outcomes compared with patients with pure DOA. Except in the temporal quadrant, RNFL measurements were significantly thinner for the DOA+ group. There was an inverse correlation between average RNFL thickness and logarithm of the minimum angle of resolution (LogMAR) visual acuity (P<0.0001).

Conclusions

RGC loss in DOA is characterised by severe involvement of the temporal papillomacular bundle, with relative sparing of the nasal fibres. RNFL thinning is more pronounced in patients with DOA+ phenotypes.     

Reduction of inner retinal thickness in patients with autosomal dominant optic atrophy associated with OPA1 mutations

PURPOSE: To determine the morphologic changes in the retina in the macula and around the optic disc in patients with autosomal dominant optic atrophy (ADOA) associated with a mutation in the OPA1 gene. METHODS: Cross-sectional images of the macular area of the retina were obtained by optical coherence tomography (OCT) in patients with ADOA who had a heterozygous mutation in the OPA1 gene. There were 15 eyes of eight patients from five families: four men and four women. The average age of the patients was 48.1 years. In the OCT images, the cross sections of the sensory retina were divided manually into four areas. The thickness of the overall sensory retina and the divided areas were measured at 1 and 2 mm on the temporal, nasal, superior, and inferior sides of the fovea as well as at the fovea. The thickness of the retinal nerve fiber layer (RNFL) around the optic discs was measured by taking circular scans (3.4 mm in diameter) centered on the optic disc. The results in the patients with ADOA were compared with those from 11 normal control subjects. RESULTS: The overall thickness of the sensory retina in the macular area was significantly thinner in the patients with ADOA than in the control subjects at all points except the fovea (P < 0.0001). The RNFL in the macular area in the patients with ADOA was significantly thinner than that in control subjects at all points (P < 0.0001), especially at 1 mm from the fovea. The circumpapillary RNFL was significantly thinner at the temporal, superior, and inferior areas in patients with ADOA but not in the nasal area. The total cross-sectional area of the circumpapillary RNFL was significantly correlated with visual acuity. The thickness of the combined ganglion cell layer, inner plexiform layer, inner nuclear layer, and outer plexiform layer in the macular area was significantly thinner in the patients (P < 0.0056). The thickness of the outer nuclear layer and the photoreceptor inner segments and the thickness of the photoreceptor outer segments were not significantly different between the patients with ADOA and normal control subjects. CONCLUSIONS: The RNFL and the layer including the ganglion cell layer are significantly thinner in patients with ADOA associated with an OPA1 gene mutation, whereas the photoreceptor layers are not affected morphologically. The inner retina is the main area of the retina altered in ADOA.     

Reduction of oscillatory potentials and photopic negative response in patients with autosomal dominant optic atrophy with OPA1 mutations

PURPOSE: To study the electroretinographic (ERG) findings in patients with autosomal dominant optic atrophy (ADOA) with OPA1 mutations. METHODS: Eight ADOA patients (age range, 24-55 years; mean, 41 years) with OPA1 mutations were studied. In addition to routine ophthalmological tests, full-field ERGs including the rod response, mixed rod-cone response, oscillatory potentials (OPs), single-flash cone response, and photopic negative response (PhNR) were recorded and compared with those from 25 age-matched controls. The correlation between the ERG data and averaged retinal nerve fiber layer (RNFL) thickness around the optic disk measured by optical coherent tomography, mean deviation of the static perimetry (Humphrey 30-2 program), or corrected visual acuity was also examined. RESULTS: Amplitudes of the PhNR and OPs, both of which are believed to originate from inner retinal layers, were significantly smaller in ADOA patients than in control subjects (P < 0.01). Amplitudes of other ERG components were not statistically different in the two groups. OP amplitude was inversely correlated with the patient's age. The RNFL was thinner and the retinal sensitivities obtained by static perimetry were lower in ADOA patients, but these values were not correlated with the amplitude of PhNR or OPs. CONCLUSIONS: These results suggested that there are functional impairments not only in the ganglion cell layer but also in the inner nuclear and plexiform layers, including the amacrine cells of ADOA patients with OPA1 mutations.     

The association of autosomal dominant optic atrophy and moderate deafness may be due to the R445H mutation in the OPA1 gene

PURPOSE: To examine the involvement of the optic atrophy 1 (OPA1) gene in optic atrophy associated with moderate deafness. DESIGN: Observational case report.The entire coding sequence of the OPA1 gene was directly sequenced in the case of a patient suffering from optic atrophy associated with moderate deafness. RESULTS: A de novo heterozygous mutation R445H in the OPA1 gene was found. No similar mutation was detected in either of the patient's parents or in the 100 chromosome controls. CONCLUSION: The R445H mutation in OPA1 might be the cause of the association between dominant optic atrophy and moderate deafness, a phenotype that may be currently underdiagnosed.     

A novel OPA1 mutation responsible for autosomal dominant optic atrophy with high frequency hearing loss in a Chinese family

PURPOSE: To investigate the genetic findings and phenotypic characters of autosomal dominant optic atrophy (ADOA). DESIGN: Case report and experimental study. METHODS: Molecular genetic analysis and clinical examinations were performed in a Chinese family with ADOA. Mutations in OPA1 were detected by direct sequencing. Haplotypes were constructed and compared with the phenotypes in the family. RESULTS: Nine family members were diagnosed with ADOA and some of them were accompanied with hearing loss and/or high myopia. A novel heterozygous mutation, c.2848_2849delGA(p.Asp950CysfsX4), was detected in all ADOA patients. The mutation and the mutation bearing haplotype cosegregated with the nine affected members. One family member had high myopia without vision or hearing loss. This patient along with unaffected ones did not harbor the mutation. CONCLUSIONS: A novel mutation, c.2848_2849delGA in OPA1, was identified in a Chinese family with ADOA. This mutation is associated with hearing loss, but likely not high myopia.     

Autosomal dominant optic atrophy: penetrance and expressivity in patients with OPA1 mutations

PURPOSE: We identified families with autosomal dominant optic atrophy (ADOA), determined the number and type of OPA1 mutations, and investigated the phenotypic variation and penetrance in ADOA Australian pedigrees. DESIGN: Cross-sectional genetics study. METHODS: Probands were identified on the basis of characteristic clinical features of ADOA. We screened the OPA1 gene using single-strand conformational polymorphism, heteroduplex analysis (SSCP/HA), or by direct sequencing. Penetrance for pedigrees in which a mutation of OPA1 had been identified was calculated initially using all recruited individuals, and subanalysis was performed using only those families for which there was total recruitment of siblings. RESULTS: A total of 406 patients from 17 pedigrees were recruited, and OPA1 mutations were identified in 11/17 (65%) of these. The mean age at clinical examination was 38.2 +/- 19.9 years (median age, 35 years; range, four to 83 years). The median best-corrected visual acuity in OPA1-mutation carriers was 20/70 (range, 20/16 to hand movements [HM]). The penetrance in Australian ADOA pedigrees in the families with complete sibling recruitment was 82.5%. On the other hand, overall penetrance for all individuals harboring an OPA1 mutation was 88%. CONCLUSIONS: OPA1 mutations were identified in 11/17 (65%) of the ADOA pedigrees in this study. The penetrance in our cohort was lower than originally described (82.5% vs 98%) but higher than some recent studies since the availability of genotyping. It is anticipated that this figure would be even lower as more asymptomatic individuals are identified. There are likely to be other genetic and environmental modifiers influencing disease penetrance.     

Developmental expression profile of the optic atrophy gene product: OPA1 is not localized exclusively in the mammalian retinal ganglion cell layer

PURPOSE: Autosomal dominant optic atrophy (ADOA) is characterized by primary degeneration of retinal ganglion cells and atrophy of the optic nerve. The OPA1 gene encodes a 960-amino-acid protein. In the current study the temporal and spatial localization of OPA1 were examined in developing and adult murine ocular tissues and the adult human eye. Because the Bst/+ mouse has been postulated as a model of ADOA, the mOPA1 expression in the Bst/+ retina was also examined. METHODS: A polyclonal antibody generated against a C-terminal peptide of OPA1 was used to assess by immunohistochemistry the expression of mOPA1 in the wild-type embryonic and postnatal mouse ocular tissues and the Bst/+ retina. Western blot analyses of total proteins from a panel of adult human tissues were used to examine the expression of human OPA1, and spatial localization was assessed by immunohistochemistry. RESULTS: The ocular expression of mOPA1 begins at E15 in the inner retina in a location corresponding to that of the subsequently developing ganglion cell layer (GCL) and peaks between postnatal day (P)0 and P1 in the retina and the optic nerve. There is a sharp decline in mOPA1 expression after P2, but it is expressed at a basal level until at least P12 in the GCL, inner plexiform layer (IPL), and inner nuclear layer (INL) of the retina as well as in the optic nerve. In the adult Bst/+ retina, mOPA1 is strongly expressed in the GCL and IPL and weakly in the INL. In the adult human eye, OPA1 is expressed in the GCL, IPL, INL, and outer plexiform layer (OPL) of the retina and in the optic nerve, where it is observed only in the myelinated region. CONCLUSIONS: OPA1 is not restricted to the GCL of the mammalian retina, and its expression extends into the IPL, INL, and OPL. OPA1 is distinctly expressed in the myelinated region beyond the lamina cribrosa in the human optic nerve, whereas its expression is weaker in the mouse optic nerve. In the Bst/+ mouse retina, despite the structural defects, mOPA1 expression is comparable to that observed in the wild-type adult mouse retina. These observations suggest a wider role for OPA1 than previously anticipated.     

Prognostic DNA testing and counselling for dominant optic atrophy due to a novel OPA1 mutation

CASE REPORT: To report the case of a 26-year-old woman with a family history of dominant optic atrophy who requested DNA testing and counselling. Ophthalmologic examination showed her affected father had bilateral temporal papillary pallor. Direct genomic sequencing of the OPA1 gene revealed a novel heterozygous nonsense mutation (Arg879stop). Because no mutation in OPA1 was detected in the daughter, we could counsel her that the possibility was very low that she was a carrier or would pass the disease-causing gene to her children. COMMENTS: Our study provides evidence of the apparent value of molecular genetic analysis of OPA1 gene as predictive DNA testing, although the exact risk and benefit of this type of analysis awaits further study.     

OPA1 expression in the human retina and optic nerve

Mutations in the optic atrophy type 1 (OPA1) gene give rise to human autosomal dominant optic atrophy. The purpose of this study is to investigate OPA1 protein expression in the human retina and optic nerve. A rabbit polyclonal antiserum was generated using a fusion protein covering amino acids 647 to 808 of the human OPA1 protein as the immunogenic antigen. Western blot and immunofluorescence staining were performed to examine OPA1 expression in the human retina and optic nerve. In human retina, we found that OPA1 expression was clearly present in retinal ganglion cells and photoreceptors. OPA1 immunoreactivity was also present in the nerve fiber layer, inner plexiform layer and outer plexiform layer. However, OPA1 protein was not detected in the choline acetyltransferase-positive, calretinin-positive, and calbindin-positive amacrine cells, nor in the calbindin-positive horizontal cells. In the human optic nerve, expression of OPA1 was present in the axonal tract that was labeled with neurofilament specific antibody. In conclusion, expression of OPA1 gene is present in the mitochondria-rich regions of the retina and optic nerve. This suggests that OPA1 protein might be involved in the functioning of the mitochondria that are present in both inner and outer retinal neurons.     

A novel mutation of the type 1 optic atrophy(OPA1) gene in a Japanese family with OPA1

PURPOSE: To report a novel mutation of the type1 optic atrophy(OPA1) gene in a Japanese family with OPA1 and to describe the clinical features of this family. METHODS: Standard ocular examinations were performed on the proband and his two affected sons. The DNA sequence of all exons and splice sites of the OPA1 gene was determined to detect mutations. RESULTS: The proband and his sons had a heterozygous mutation of the OPA1 gene in the third nucleotide of intron 12(IVS12 + 3A-->T). Clinically, each patient had reduced visual acuity(onset within the first 6 years of life) and optic nerve pallor. The proband showed a central scotoma and generalized dyschromatopsia. This is the first report of OPA1 gene mutation in Japanese patients with familial optic atrophy. CONCLUSIONS: A mutation of the OPA1 gene was detected in a Japanese family with OPA1, which follows the same pattern as reported in Western countries. It is suggested that mutations of the OPA1 gene contribute to the development of optic nerve atrophy regardless of ethnic groups. Screening for the OPA1 gene mutation will be useful for diagnosis of OPA1 in Japanese patients.     

Structural model of the OPA1 GTPase domain may explain the molecular consequences of a novel mutation in a family with autosomal dominant optic atrophy

Autosomal dominant optic atrophy (ADOA) is the most frequent hereditary optic neuropathy. Three loci have been reported for ADOA: a major locus, harboring all identified mutations to date, maps to 3q28 (OPA1), a second locus is linked to 18q12.2-q12.3 (OPA4) and a third locus on 22q12.1-q13.1 (OPA5) has been reported recently. We describe a six-generation Iranian family in which optic atrophy runs as an autosomal dominant trait with an age of onset at 14-15years. We performed linkage analysis with markers mapping to 3q28 and 18q12.2-q12.3 and found linkage to 3q28. Subsequent sequencing of OPA1 identified a novel heterozygous missense mutation (c.1313A>G) replacing aspartic acid by glycine (p.D438G) in the GTPase domain of OPA1. Interestingly, another missense mutation at the same position (c.1313A>T, D438V) has been reported before in two unrelated German families, indicating a possible mutation hot spot. Further evidence supporting the importance of D438 is its conservation from human to acoelomata. OPA1 is believed to be the human orthologue of yeast MGM1, a dynamin-related protein required for the integrity of mitochondrial DNA. Homology modeling of the OPA1 GTPase domain revealed extensive structural similarity to the Dictyostelium dynamin A GTPase domain and showed that D438 may interact with residues of the G1 and the G4 motifs, which are crucial in coordinating GTP. Based on this analysis, we propose a mechanism which explains the gradual decline of vision in ADOA patients with OPA1 mutations at position 438.