Novel mutations of the OPA1 gene in Chinese dominant optic atrophy

Concurrent OPA1 mutation and chromosome 3q deletion leading to Behr syndrome: a case report

Background

Optic atrophy 1 (OPA1) gene mutations are associated with dominantly inherited optic neuropathy resulting in a progressive loss of visual acuity. Compound heterozygous or homozygous variants that lead to severe phenotypes, including Behr syndrome, have been reported rarely.

Case presentation

Here, we present a 14-month-old boy with early onset optic atrophy, congenital cataracts, neuromuscular disorders, mental retardation, and developmental delay. Combined genetic testing, including whole exome sequencing (WES) and chromosomal microarray analysis, revealed a concurrent OPA1 variant (c.2189 T > C p.Leu730Ser) and de novo chromosome 3q deletion as pathogenic variants leading to the severe phenotype.

Conclusions

Our case is the first reporting a novel missense OPA1 variant co-occurring with a chromosomal microdeletion leading to a severe phenotype reminiscent of Behr syndrome. This expands the mutation spectrum of OPA1 and inheritance patterns of this disease.

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.

Multiethnic involvement in autosomal-dominant optic atrophy in Singapore

PurposeAutosomal-dominant optic atrophy (ADOA), often associated with mutations in the OPA1 gene (chromosome 3q28-q29) is rarely reported in Asia. Our aim was to identify and describe this condition in an Asian population in Singapore.Patients and methodsPreliminary cross-sectional study at the Singapore National Eye Centre, including patients with clinical suspicion of ADOA, who subsequently underwent genetic testing by direct sequencing of the OPA1 gene.ResultsAmong 12 patients (10 families) with clinically suspected ADOA, 7 patients (5 families) from 3 different ethnic origins (Chinese, Indian, and Malay) carried a heterozygous pathogenic variant in the OPA1 gene. The OPA1 mutations were located on exons 8, 9, 11, and 17: c.869G>A (p.Arg290Glu), c.892A>G (p.Ser298Gly), c.1140G>A (splicing mutation), and c.1669C>T (p.Arg557*), respectively. One splicing mutation (c.871-1G>A) was identified in intron 8. We also identified a novel mutation causing optic atrophy and deafness (c.892A>G (p.Ser298Gly)). Among the phenotypic features, colour pupillometry disclosed a dissociation between low vision and preserved pupillary light reflex in ADOA.ConclusionWe report the first cases of genetically confirmed OPA1-related ADOA from Singapore, including a novel mutation causing 'ADOA plus' syndrome. Further epidemiological studies are needed in order to determine the prevalence of ADOA in South-East Asia.