Primary Leber's Hereditary Optic Neuropathy Research Articles

Digenic Leigh syndrome on the background of the m.11778G>A Leber hereditary optic neuropathy variant.

Leigh syndrome spectrum (LSS) is a primary mitochondrial disorder defined neuropathologically by a subacute necrotizing encephalomyelopathy and characterized by bilateral basal ganglia and/or brainstem lesions. LSS is associated with variants in several mitochondrial DNA genes and more than 100 nuclear genes, most often related to mitochondrial complex I (CI) dysfunction. Rarely, LSS has been reported in association with primary Leber hereditary optic neuropathy (LHON) variants of the mitochondrial DNA, coding for CI subunits (m.3460G>A in MT-ND1, m.11778G>A in MT-ND4 and m.14484T>C in MT-ND6). The underlying mechanism by which these variants manifest as LSS, a severe neurodegenerative disease, as opposed to the LHON phenotype of isolated optic neuropathy, remains an open question. Here, we analyse the exome sequencing of six probands with LSS carrying primary LHON variants, and report digenic co-occurrence of the m.11778G > A variant with damaging heterozygous variants in nuclear disease genes encoding CI subunits as a plausible explanation. Our findings suggest a digenic mechanism of disease for m.11778G>A-associated LSS, consistent with recent reports of digenic disease in individuals manifesting with LSS due to biallelic variants in the recessive LHON-associated disease gene DNAJC30 in combination with heterozygous variants in CI subunits.

Genetic Screening for OPA1 and OPA3 Mutations in Patients with Suspected Inherited Optic Neuropathies

Autosomal-dominant optic atrophy (DOA) is one of the most common inherited optic neuropathies, and it is genetically heterogeneous, with mutations in both OPA1 and OPA3 known to cause disease. Approximately 60% of cases harbor OPA1 mutations, whereas OPA3 mutations have been reported in only 2 pedigrees with DOA and premature cataracts. The aim of this study was to determine the yield of OPA1 and OPA3 screening in a cohort of presumed DOA cases referred to a tertiary diagnostic laboratory. Retrospective case series. One hundred eighty-eight probands with bilateral optic atrophy referred for molecular genetic investigations at a tertiary diagnostic facility: 38 patients with an autosomal-dominant pattern of inheritance and 150 sporadic cases. OPA1 and OPA3 genetic testing was initially performed using polymerase chain reaction-based sequencing methods. The presence of large-scale OPA1 and OPA3 genomic rearrangements was assessed further with a targeted comparative genomic hybridization microarray platform. The 3 primary Leber hereditary optic neuropathy (LHON) mutations, m.3460G→>A, m.11778G→A, and m.14484T→C, also were screened in all patients. The proportion of patients with OPA1 and OPA3 pathogenic mutations. The clinical profile observed in molecularly confirmed DOA cases. Twenty-one different OPA1 mutations were found in 27 (14.4%) of the 188 probands screened. The mutations included 6 novel pathogenic variants and the first reported OPA1 initiation codon mutation at c.1A→T. An OPA1 missense mutation, c.239A→G (p.Y80C), was identified in an 11-year-old black girl with optic atrophy and peripheral sensorimotor neuropathy in her lower limbs. The OPA1 detection rate was significantly higher among individuals with a positive family history of visual failure (50.0%) compared with sporadic cases (5.3%). The primary LHON screen was negative in the patient cohort, and additional molecular investigations did not reveal any large-scale OPA1 rearrangements or OPA3 genetic defects. The mean baseline visual acuity for the OPA1-positive group was 0.48 logarithm of the minimum angle of resolution (units mean Snellen equivalent, 20/61; range, 20/20-20/400; 95% confidence interval, 20/52-20/71), and visual deterioration occurred in 54.2% of patients during follow-up. OPA1 mutations are the most common genetic defects identified in patients with suspected DOA, whereas OPA3 mutations are very rare in isolated optic atrophy cases.

Sporadic Bilateral Optic Neuropathy in Children: The Role of Mitochondrial Abnormalities

To evaluate a group of patients with isolated, early-onset, bilateral optic neuropathy for genetic and biochemical evidence of mitochondrial diseases. This case-control study involved 21 patients, 159 control subjects for mitochondrial (mt)DNA sequencing, and 40 control subjects for relative mtDNA content. Patients were identified who had had decreased vision since childhood due to bilateral optic neuropathy characterized by central visual loss with no other major neurologic or ocular abnormality and no clinical evidence of a mitochondrial syndrome. Clinical examination, electroretinograms, and neuroimaging were performed; the entire mtDNA coding region was sequenced in leukocytes of all patients; relative mtDNA content was assessed; and OPA1 and OPA3 nuclear genes associated with dominant and recessive optic atrophy, respectively, were sequenced. Main outcome measures were clinical description, nonsynonymous (NS) mtDNA nucleotide changes, relative mtDNA content, and OPA1 and OPA3 nucleotide changes. Twenty-one unrelated patients (16 male and 5 female; mean age at first examination 13.6 years) had bilateral moderate, relatively symmetric optic neuropathies and normal neurologic examinations other than strabismus in 11 and congenital nystagmus in 9. Four patients had optic nerve hypoplasia. One patient had the nt 11778 primary Leber hereditary optic neuropathy (LHON) mutation, and three others had mtDNA nucleotide changes predicted to be pathologic. The entire group had a small increase (6.7%) in relative mtDNA content of indeterminate statistical significance. No patient had a polymorphism or mutation of OPA1 or OPA3. A minority of these young patients with sporadic bilateral optic neuropathy had abnormalities of the mitochondrial parameters evaluated. This bilateral optic neuropathy may be due to other genetic, epigenetic, or environmental injury to the optic nerve or to mitochondrial defects not studied.