Clinical heterogeneity in autosomal dominant optic atrophy in two 3q28-qter linked central Illinois families

Meta-analysis of genotype-phenotype analysis of OPA1 mutations in autosomal dominant optic atrophy

Autosomal Dominant Optic Atrophy (ADOA) is a neuro-ophthalmic disease characterized by progressive bilateral vision loss, pallor of the optic disc, central vision loss, and impairment of color vision. Additionally, a small percentage of patients experience hearing loss and ataxia, while recent studies suggest disruption of cardiac and neuromuscular functions. In order to obtain a better understanding of the genotype-phenotype correlation of the various mutations in the optic atrophy 1 (OPA1) gene, we obtained both clinical and genetic information of ADOA patients from published reports. We conducted a systematic review of published OPA1 literature and identified 408 individuals with confirmed OPA1 mutations, 120 of whom reported extra-ocular (ADOA 'plus') manifestations through their descriptions of visual and multi-systemic symptoms. Our results show that there is a significant variation in frequency of the specific exons involved between the ADOA classic and ADOA 'plus' patients. Classic ADOA groups were more likely to have mutations in exon 8 and 9, while ADOA 'plus' groups were more likely to have mutations in exons 14, 15 and 17. Additional comparisons revealed significant differences between mutation types/domains and specific ADOA 'plus' manifestations. We also found that individuals with maternally inherited OPA1 mutations were significantly more likely to develop 'plus' manifestations than those with paternally inherited mutations. Overall, this study provides novel information regarding genotype-phenotype correlations of ADOA which warrants additional recommendations added to the current clinical management of ADOA patients.

Long-Term Follow-Up Study of Autosomal Dominant Optic Atrophy in an Australian Population

PURPOSE

This study aimed to describe the phenotype of Australian patients with a clinical diagnosis of dominant optic atrophy (DOA) and provide long-term follow-up data on its natural history.

DESIGN

Retrospective analysis.

METHODS

All patients with the clinical diagnosis of DOA observed during a 30-year period at a single tertiary referral center (Save Sight Institute, Sydney Eye Hospital, Sydney, Australia) with at least 12 months of follow-up were included in the study. Clinical characteristics were assessed with particular attention to change in visual acuity (VA).

RESULTS

There were 36 patients with DOA from 26 different Australian families. The most common clinical presentation of DOA was insidious onset of visual difficulties beginning in childhood. Mean (SD) age at diagnosis of DOA was 16 (14) years. During a mean follow-up period of 10.6 years (median, 10 years), 44% of study eyes had no change in VA, 35% had reduction of VA by 1 Snellen line, 13% had a reduction of VA by 2 Snellen lines, and 8% of the study eyes had a VA reduction of more than 2 Snellen lines. Six of 36 patients were legally blind at last follow-up.

CONCLUSIONS

There is considerable heterogeneity in the presenting VA and natural history of DOA between individual patients and within families with DOA, with VA ranging from 6/6 to hand motion perception. This study provides valuable information to aid the clinician counseling the long-term visual outcome in patients with DOA and their families.

The molecular mechanisms of OPA1-mediated optic atrophy in Drosophila model and prospects for antioxidant treatment

Mutations in optic atrophy 1 (OPA1), a nuclear gene encoding a mitochondrial protein, is the most common cause for autosomal dominant optic atrophy (DOA). The condition is characterized by gradual loss of vision, color vision defects, and temporal optic pallor. To understand the molecular mechanism by which OPA1 mutations cause optic atrophy and to facilitate the development of an effective therapeutic agent for optic atrophies, we analyzed phenotypes in the developing and adult Drosophila eyes produced by mutant dOpa1 (CG8479), a Drosophila ortholog of human OPA1. Heterozygous mutation of dOpa1 by a P-element or transposon insertions causes no discernable eye phenotype, whereas the homozygous mutation results in embryonic lethality. Using powerful Drosophila genetic techniques, we created eye-specific somatic clones. The somatic homozygous mutation of dOpa1 in the eyes caused rough (mispatterning) and glossy (decreased lens and pigment deposition) eye phenotypes in adult flies; this phenotype was reversible by precise excision of the inserted P-element. Furthermore, we show the rough eye phenotype is caused by the loss of hexagonal lattice cells in developing eyes, suggesting an increase in lattice cell apoptosis. In adult flies, the dOpa1 mutation caused an increase in reactive oxygen species (ROS) production as well as mitochondrial fragmentation associated with loss and damage of the cone and pigment cells. We show that superoxide dismutase 1 (SOD1), Vitamin E, and genetically overexpressed human SOD1 (hSOD1) is able to reverse the glossy eye phenotype of dOPA1 mutant large clones, further suggesting that ROS play an important role in cone and pigment cell death. Our results show dOpa1 mutations cause cell loss by two distinct pathogenic pathways. This study provides novel insights into the pathogenesis of optic atrophy and demonstrates the promise of antioxidants as therapeutic agents for this condition.

Optic atrophies are a group of neurodegenerative disorders characterized by a gradual loss of vision, color vision defects, and temporal optic pallor. Autosomal dominant optic atrophy (DOA), a type of optic atrophy, contributes to a large portion of optic atrophy cases. Mutations of the optic atrophy 1 (OPA1) gene are responsible for this condition. Here we describe mutant Drosophila that contain insertions in the Drosophila OPA1 ortholog, dOpa1. Heterozygous mutation causes no discernable eye phenotype, and homozygous mutation results in embryonic lethality. Using the powerful Drosophila genetic techniques, we created eye-specific mutants, giving rise to cells with two mutant copies of dOpa1 only in the Drosophila eye, and found that these eyes were rough (mispatterned) and glossy (decreased lens and pigment deposition). We found that these phenotypes were associated with fragmented mitochondria and were caused by elevated reactive oxygen species. The administration of antioxidants could ameliorate the phenotypes caused by mutation of dOpa1, offering new insight into treatment of this disease.

Dominant optic atrophy: correlation between clinical and molecular genetic studies

PURPOSE

To assess the clinical picture and molecular genetics of 14 Finnish families with dominant optic atrophy (DOA).

METHODS

The clinical status of family members was based on the assessment of visual acuity, colour vision, visual fields and optic nerve appearance; 31 individuals were affected, two suspect and 21 unaffected. A total of 30 coding exons and exon- intron boundaries of the OPA1 gene were sequenced in order to detect mutations.

RESULTS

Half the patients were diagnosed at the age of < or = 20 years. Ten out of 20 affected individuals followed up for > or = 6 years had a progressive disease and 10 had a stable disease. According to WHO criteria, 36% of the affected patients were visually handicapped. Eight OPA1 pathogenic mutations, all but one novel, and 18 neutral polymorphisms were detected.

CONCLUSION

The most sensitive indicators of DOA were optic disc pallor and dyschromatopsia. With molecular genetic analysis, asymptomatic mutation carriers and DOA cases with a mild clinical outcome were ascertained. No mutational hotspot or Finnish major mutation in the OPA1 gene could be demonstrated as most families carried a unique mutation. No obvious genotype- phenotype correlation could be detected. Detailed clinical assessment and exclusion of non-DOA families prior to mutation screening are necessary for obtaining a high mutation detection rate.